PENGUIN BOOKS

THE BLANK SLATE

Steven Pinker is Johnstone Professor of Psychology at Harvard University. His research on visual cognition and the psychology of language has earned prizes from the National Academy of Sciences and the American Psychological Association. Pinker has also received many awards for his teaching at MIT and for his books How the Mind Works (which was also a finalist for the Pulitzer Prize) and The Language Instinct. He is an elected fellow of several scientific societies, associate editor of Cognition, and a member of the usage panel of the American Heritage Dictionary. He has written for The New York Times, Time, The New Yorker, The New Republic, Slate, and Technology Review.

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Praise for The Blank Slate

“A brilliant and forceful summary... A well-informed and well-written account of [human] limitations, [written with] a graceful interleaving of scientific and literary sources.... [This] fine book helps with a task that we all must begin to take seriously... Can it be that we have finally grown up?”

— Melvin Konner, The American Prospect

“This is a brilliant book. It is beautifully written, and addresses profound issues with courage and clarity. There is nothing else like it, and it is going to have an impact that extends well beyond the scientific academy.”

— Paul Bloom, Trends in Cognitive Sciences

“Steven Pinker has written an extremely good book — clear, well argued, fair, learned, tough, witty, humane, stimulating. I only hope that people study it carefully before rising up ideologically against him. If they do, they will see that the idea of an innately flawed but wonderfully rich human nature is a force for good, not evil.

— Colin McGinn, The Washington Post

“Steven Pinker is a man of encyclopedic knowledge and an incisive style of argument. His argument in The Blank Slate is that intellectual life in the West, and much of our social and political policy, was increasingly dominated through the twentieth century by a view of human nature that is fundamentally flawed; that this domination has been backed by something that amounts to academic terrorism (he does not put it quite so strongly): and that we would benefit  {ii}  substantially from a more realistic view. Pinker's exposition is thoroughly readable and of enviable clarity. His explanation of such a difficult technical matter as the analysis of variance and regression in twin studies, for example, would be very hard to better. He is not afraid of using strong language... in addition, parts of the book are delightfully funny.”

— John R. G. Turner, The Times Literary Supplement

“Anyone who has read Pinker's earlier books — including How the Mind Works and The Language Instinct — will rightly guess that his latest effort is similarly sweeping, erudite, sharply argued, richly footnoted and fun to read. It's also highly persuasive.”

— Michael Lemonick, Time

“[Pinker] makes his main argument persuasively and with great verve...

The Blank Slate ought to be read by anybody who feels they have had enough of nature-nurture rows or who thinks they already know where they stand on the science wars. It could change their minds... If nothing else, Mr. Pinker's book is a wonderfully readable taster of new research, much of it ingenious, designed to show that many more of our emotional biases and mental aptitudes than previously thought are hard-wired or, to use the old word, innate... This is a breath of air for a topic that has been politicized for too long.”

— The Economist

“[Pinker] wades resolutely into the comforting gloom surrounding these not quite forbidden topics and calmly, lucidly marshals the facts to ground his strikingly subversive Darwinian claims — subversive not of any of the things we properly hold dear but subversive of the phony protective layers of misinformation surrounding them... My reservations with Pinker's view [will be resolved] in the bright light of rational inquiry that he brings to these important topics.”

— Dan Dennett, The Times Literary Supplement

“The Blank Slate brilliantly delineates the current state of play in the nature-nurture debate. Read it to understand not just the moral and aesthetic blindness of your friends, but the misguided idealism of nations. A magnificent and timely work.”

— Fay Weldon, The Daily Telegraph

“[Pinker] points us in the direction of a more productive debate, a debate in which the implications of science are confronted forthrightly and not simply wished away by politicized scientists.”

— Francis Fukuyama, The Wall Street Journal  {iii} 

“The Blank Slate is... a stylish piece of work. I won't say it is better than The Language Instinct or How the Mind Works, but it is as good — which is very high praise indeed. What a superb thinker and writer he is: what a role model to young scientists. And how courageous to buck the liberal trend in science, while remaining in person the best sort of liberal. Pinker is a star, and the world of science is lucky to have him.”

— Richard Dawkins, The Times Literary Supplement

“The Blank Slate is not dismal at all, but unexpectedly bracing. It feels a bit like being burgled. You're shocked, your things are gone, but you can't help thinking about how you're going to replace them. What Steven Pinker has done is break into our common human home and steal our illusions.”

— John Morrish, The Independent

“As a brightly lighted path between what we would like to believe and what we need to know, [The Blank Slate] is required reading. Pinker presents an unanswerable case for accepting that man can be, as he is, both wired and free.”

— Frederic Raphael, Los Angeles Times

“Pinker's thinking and writing are first-rate; maybe even better than that. The Blank Slate is much-needed, long overdue and — if you are interested in what might be called the ‘human nature wars’ — somewhere between that old standby, ‘required reading,’ and downright indispensable. It is unlikely to change the minds of those who are rigidly committed to the blank slate perspective, but for anyone whose ‘nature’ includes even a modicum of open-mindedness, it should prove a revelation.”

— David Barash, Human Nature Review

“Pinker is one of those rare writers who is at once persuasive and comprehensive, informative and entertaining.”

— Kevin Shapiro, Commentary

“The fight for a separation of politics from science is an eminently sensible, logical, and ultimately humanistic task, and it took someone as brave as Pinker to dedicate himself to it....[This is a] necessary book, a book that in a more truthful intellectual climate — one open to the idea that any knowledge about ourselves can only enhance our ability to act well and compassionately — would not have had to be written. In this climate, however, we should be grateful that it was.”

— Daniel Smith, The Boston Globe  {iv} 

“The Blank Slate deserves to be read carefully and with an open mind... This landmark book makes an important contribution to the argument about nature vs. nurture in humans. Whether or not most readers end up on Pinker's side of the fence, one can hope that his thoroughness and reasoning will shed light into the darker corners where research has been suppressed by taboos, and where freedom of thought and speech have been inhibited by fear of consequences for asking forbidden questions.”

— Nancy Jeannette Friedlander, The San Diego Union-Tribune

“This book is a modern magnum opus. The scholarship alone is mind-boggling, a monument of careful research, meticulous citation, breadth of input from diverse fields, great writing and humor.”

— Tom Paskal, The Montreal Gazette

“A delightfully provocative read... A constantly dynamic, if tacit, exchange between the author and his readers.”

— Patrick Watson, The Globe and Mail

“A feast of a book. Pinker's analytical and impish mind ranges from Charles Darwin to Abigail Van Buren, from scientific studies to Annie Hall.... It will be a rare reader who agrees with everything in this book. But it is an intelligent book that says what it means and thinks about what it is saying.... Though much of the book is about human differences, the bigger idea is inherited similarity — the ‘psychological unity of our species.’ It is not a blank slate but a slate with a face — a face that might be called human nature. When Pinker starts describing it, the reader will surely recognize it.”

— Bruce Ramsey, The Seattle Times

THE BLANK SLATE

The Modern Denial
of Human Nature

Steven Pinker

PENGUIN BOOKS

To Don, Judy, Leda, and John

PENGUIN BOOKS

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Copyright © Steven Pinker, 2002
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Grateful acknowledgment is made for permission to reprint the following copyrighted material. Page 22: Lyrics from “A Simple Desultory Philippic (or How I Was Robert McNamara'd into Submission)”; copyright © 1965, Paul Simon; used by permission of the publisher: Paul Simon Music. Page 57: Chart, “Percentage of Male Deaths Caused by Warfare,” from War Before Civilization by Lawrence H. Keeley, copyright © 1996 by Oxford University Press, Inc.; used by permission of Oxford University Press, Inc. Page 88: Diagram of the wiring of the primate visual system from Michael Gazzaniga, The Cognitive Neurosciences, The MIT Press (1996). Page 179: Lyrics from “Gee, Officer Krupke” by Leonard Bernstein & Stephen Sondheim; © 1956, Amberson Holdings LLC and Stephen Sondheim; copyright renewed; Leonard Bernstein Music Publishing Company LLC, publisher; used by permission. Page 199: Diagram, “Turning the Tables,” from Mind Sights by Roger N. Shepard, © 1990 by Roger N. Shepard; reprinted by permission of Henry Holt and Company, LLC. “Checker Shadow Illusion” © Edward Adelson, 2002; reprinted with permission. Page 326: Lyrics from “You Don't Mess Around with Jim,” written by Jim Croce; © 1972 (renewed), Time in a Bottle/Croce Publishing (ASCAP); all rights reserved; used by permission.

THE LIBRARY OF CONGRESS HAS CATALOGUED THE HARDCOVER EDITION AS FOLLOWS:
Pinker, Steven, 1954-
The blank slate : the modern denial of human nature / Steven Pinker.
p. cm.
Includes bibliographical references (p.) and index.
ISBN 0-670-03151-8 (hc.)
ISBN 0 14 20.0334 4 (pbk.)
1. Nature and nurture. I. Title.
BF341.P47 2002 155.2'34 — dc21 2002022719

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PREFACE

“Not another book on nature and nurture! Are there really people out there who still believe that the mind is a blank slate? Isn't it obvious to anyone with more than one child, to anyone who has been in a heterosexual relationship, or to anyone who has noticed that children learn language but house pets don't, that people are born with certain talents and temperaments? Haven't we all moved beyond the simplistic dichotomy between heredity and environment and realized that all behavior comes out of an interaction between the two?”

This is the kind of reaction I got from colleagues when I explained my plans for this book. At first glance the reaction is not unreasonable. Maybe nature versus nurture is a dead issue. Anyone familiar with current writings on mind and behavior has seen claims to the middle ground like these:

If the reader is now convinced that either the genetic or environmental explanation has won out to the exclusion of the other, we have not done a sufficiently good job of presenting one side or the other. It seems highly likely to us that both genes and environment have something to do with this issue. What might the mix be? We are resolutely agnostic on that issue; as far as we can determine, the evidence does not yet justify an estimate.

This is not going to be one of those books that says everything is genetic: it isn't. The environment is just as important as the genes. The things children experience while they are growing up are just as important as the things they are born with.

Even when a behavior is heritable, an individual's behavior is still a product of development, and thus it has a causal environmental component.... The modern understanding of how phenotypes are inherited through the replication of both genetic and environmental  {viii}  conditions suggests that... cultural traditions — behaviors copied by children from their parents — are likely to be crucial.

If you think these are innocuous compromises that show that everyone has outgrown the nature-nurture debate, think again. The quotations come, in fact, from three of the most incendiary books of the last decade. The first is from The Bell Curve by Richard Herrnstein and Charles Murray, who argue that the difference in average IQ scores between American blacks and American whites has both genetic and environmental causes.¹ The second is from The Nurture Assumption by Judith Rich Harris, who argues that children's personalities are shaped by their genes as well as by their environments, so similarities between children and their parents may come from their shared genes and not just from the effects of parenting.² The third is from A Natural History of Rape by Randy Thornhill and Craig Palmer, who argue that rape is not simply a product of culture but also has roots in the nature of men's sexuality.³ For invoking nurture and nature, not nurture alone, these authors have been picketed, shouted down, subjected to searing invective in the press, even denounced in Congress. Others expressing such opinions have been censored, assaulted, or threatened with criminal prosecution.⁴

The idea that nature and nurture interact to shape some part of the mind might turn out to be wrong, but it is not wishy-washy or unexceptionable, even in the twenty-first century, thousands of years after the issue was framed. When it comes to explaining human thought and behavior, the possibility that heredity plays any role at all still has the power to shock. To acknowledge human nature, many think, is to endorse racism, sexism, war, greed, genocide, nihilism, reactionary politics, and neglect of children and the disadvantaged. Any claim that the mind has an innate organization strikes people not as a hypothesis that might be incorrect but as a thought it is immoral to think.

This book is about the moral, emotional, and political colorings of the concept of human nature in modern life. I will retrace the history that led people to see human nature as a dangerous idea, and I will try to unsnarl the moral and political rat's nests that have entangled the idea along the way. Though no book on human nature can hope to be uncontroversial, I did not write it to be yet another “explosive” book, as dust jackets tend to say. I am not, as many people assume, countering an extreme “nurture” position with an extreme “nature” position, with the truth lying somewhere in between. In some cases, an extreme environmentalist explanation is correct: which language you speak is an obvious example, and differences among races and ethnic groups in test scores may be another. In other cases, such as certain inherited neurological disorders, an extreme hereditarian explanation is correct. In most cases the correct explanation will invoke a complex interaction between heredity and environment: culture is crucial, but culture could not exist without mental  {ix}  faculties that allow humans to create and learn culture to begin with. My goal in this book is not to argue that genes are everything and culture is nothing — no one believes that — but to explore why the extreme position (that culture is everything) is so often seen as moderate, and the moderate position is seen as extreme.

Nor does acknowledging human nature have the political implications so many fear. It does not, for example, require one to abandon feminism, or to accept current levels of inequality or violence, or to treat morality as a fiction. For the most part I will try not to advocate particular policies or to advance the agenda of the political left or right. I believe that controversies about policy almost always involve tradeoffs between competing values, and that science is equipped to identify the tradeoffs but not to resolve them. Many of these tradeoffs, I will show, arise from features of human nature, and by clarifying them I hope to make our collective choices, whatever they are, better informed. If I am an advocate, it is for discoveries about human nature that have been ignored or suppressed in modern discussions of human affairs.

Why is it important to sort this all out? The refusal to acknowledge human nature is like the Victorians’ embarrassment about sex, only worse: it distorts our science and scholarship, our public discourse, and our day-to-day lives. Logicians tell us that a single contradiction can corrupt a set of statements and allow falsehoods to proliferate through it. The dogma that human nature does not exist, in the face of evidence from science and common sense that it does, is just such a corrupting influence.

First, the doctrine that the mind is a blank slate has distorted the study of human beings, and thus the public and private decisions that are guided by that research. Many policies on parenting, for example, are inspired by research that finds a correlation between the behavior of parents and the behavior of children. Loving parents have confident children, authoritative parents (neither too permissive nor too punitive) have well-behaved children, parents who talk to their children have children with better language skills, and so on. Everyone concludes that to grow the best children, parents must be loving, authoritative, and talkative, and if children don't turn out well it must be the parents’ fault. But the conclusions depend on the belief that children are blank slates. Parents, remember, provide their children with genes, not just a home environment. The correlations between parents and children may be telling us only that the same genes that make adults loving, authoritative, and talkative make their children self-confident, well-behaved, and articulate. Until the studies are redone with adopted children (who get only their environment, not their genes, from their parents), the data are compatible with the possibility that genes make all the difference, the possibility that parenting makes all the difference, or anything in between. Yet in almost every instance, the most extreme position — that parents are everything — is the only one researchers entertain.  {x} 

The taboo on human nature has not just put blinkers on researchers but turned any discussion of it into a heresy that must be stamped out. Many writers are so desperate to discredit any suggestion of an innate human constitution that they have thrown logic and civility out the window. Elementary distinctions — “some” versus “all,” “probable” versus “always,” “is” versus “ought” — are eagerly flouted to paint human nature as an extremist doctrine and thereby steer readers away from it. The analysis of ideas is commonly replaced by political smears and personal attacks. This poisoning of the intellectual atmosphere has left us unequipped to analyze pressing issues about human nature just as new scientific discoveries are making them acute.

The denial of human nature has spread beyond the academy and has led to a disconnect between intellectual life and common sense. I first had the idea of writing this book when I started a collection of astonishing claims from pundits and social critics about the malleability of the human psyche: that little boys quarrel and fight because they are encouraged to do so; that children enjoy sweets because their parents use them as a reward for eating vegetables; that teenagers get the idea to compete in looks and fashion from spelling bees and academic prizes; that men think the goal of sex is an orgasm because of the way they were socialized. The problem is not just that these claims are preposterous but that the writers did not acknowledge they were saying things that common sense might call into question. This is the mentality of a cult, in which fantastical beliefs are flaunted as proof of one's piety. That mentality cannot coexist with an esteem for the truth, and I believe it is responsible for some of the unfortunate trends in recent intellectual life. One trend is a stated contempt among many scholars for the concepts of truth, logic, and evidence. Another is a hypocritical divide between what intellectuals say in public and what they really believe. A third is the inevitable reaction: a culture of “politically incorrect” shock jocks who revel in anti-intellectualism and bigotry, emboldened by the knowledge that the intellectual establishment has forfeited claims to credibility in the eyes of the public.

Finally, the denial of human nature has not just corrupted the world of critics and intellectuals but has done harm to the lives of real people. The theory that parents can mold their children like clay has inflicted childrearing regimes on parents that are unnatural and sometimes cruel. It has distorted the choices faced by mothers as they try to balance their lives, and multiplied the anguish of parents whose children haven't turned out the way they hoped. The belief that human tastes are reversible cultural preferences has led social planners to write off people's enjoyment of ornament, natural light, and human scale and force millions of people to live in drab cement boxes. The romantic notion that all evil is a product of society has justified the release of dangerous psychopaths who promptly murdered innocent people. And the conviction  {xi}  that humanity could be reshaped by massive social engineering projects led to some of the greatest atrocities in history.

Though many of my arguments will be coolly analytical — that an acknowledgment of human nature does not, logically speaking, imply the negative outcomes so many people fear — I will not try to hide my belief that they have a positive thrust as well. “Man will become better when you show him what he is like,” wrote Chekhov, and so the new sciences of human nature can help lead the way to a realistic, biologically informed humanism. They expose the psychological unity of our species beneath the superficial differences of physical appearance and parochial culture. They make us appreciate the wondrous complexity of the human mind, which we are apt to take for granted precisely because it works so well. They identify the moral intuitions that we can put to work in improving our lot. They promise a naturalness in human relationships, encouraging us to treat people in terms of how they do feel rather than how some theory says they ought to feel. They offer a touchstone by which we can identify suffering and oppression wherever they occur, unmasking the rationalizations of the powerful. They give us a way to see through the designs of self-appointed social reformers who would liberate us from our pleasures. They renew our appreciation for the achievements of democracy and of the rule of law. And they enhance the insights of artists and philosophers who have reflected on the human condition for millennia.

An honest discussion of human nature has never been more timely. Throughout the twentieth century, many intellectuals tried to rest principles of decency on fragile factual claims such as that human beings are biologically indistinguishable, harbor no ignoble motives, and are utterly free in their ability to make choices. These claims are now being called into question by discoveries in the sciences of mind, brain, genes, and evolution. If nothing else, the completion of the Human Genome Project, with its promise of an unprecedented understanding of the genetic roots of the intellect and the emotions, should serve as a wake-up call. The new scientific challenge to the denial of human nature leaves us with a challenge. If we are not to abandon values such as peace and equality, or our commitments to science and truth, then we must pry these values away from claims about our psychological makeup that are vulnerable to being proven false.

This book is for people who wonder where the taboo against human nature came from and who are willing to explore whether the challenges to the taboo are truly dangerous or just unfamiliar. It is for those who are curious about the emerging portrait of our species and curious about the legitimate criticisms of that portrait. It is for those who suspect that the taboo against human nature has left us playing without a full deck as we deal with the pressing issues confronting us. And it is for those who recognize that the sciences of  {xii}  mind, brain, genes, and evolution are permanently changing our view of ourselves and wonder whether the values we hold precious will wither, survive, or (as I argue) be enhanced.

~

It is a pleasure to acknowledge the friends and colleagues who improved this book in innumerable ways. Helena Cronin, Judith Rich Harris, Geoffrey Miller, Orlando Patterson, and Donald Symons offered deep and insightful analyses of every aspect, and I can only hope that the final version is worthy of their wisdom. I profited as well from invaluable comments by Ned Block, David Buss, Nazli Choucri, Leda Cosmides, Denis Dutton, Michael Gazzaniga, David Geary, George Graham, Paul Gross, Marc Hauser, Owen Jones, David Kemmerer, David Lykken, Gary Marcus, Roslyn Pinker, Robert Plomin, James Rachels, Thomas Sowell, John Tooby, Margo Wilson, and William Zimmerman. My thanks also go to the colleagues who reviewed chapters in their areas of expertise: Josh Cohen, Richard Dawkins, Ronald Green, Nancy Kanwisher, Lawrence Katz, Glenn Loury, Pauline Maier, Anita Patterson, Mriganka Sur, and Milton J. Wilkinson.

I thank many others who graciously responded to requests for information or offered suggestions that found their way into the book: Mahzarin Banaji, Chris Bertram, Howard Bloom, Thomas Bouchard, Brian Boyd, Donald Brown, Jennifer Campbell, Rebecca Cann, Susan Carey, Napoleon Chagnon, Martin Daly, Irven DeVore, Dave Evans, Jonathan Freedman, Jennifer Ganger, Howard Gardner, Tamar Gendler, Adam Gopnik, Ed Hagen, David Housman, Tony Ingram, William Irons, Christopher Jencks, Henry Jenkins, Jim Johnson, Erica Jong, Douglas Kenrick, Samuel Jay Keyser, Stephen Kosslyn, Robert Kurzban, George Lakoff, Eric Lander, Loren Lomasky, Martha Nussbaum, Mary Parlee, Larry Squire, Wendy Steiner, Randy Thornhill, James Watson, Torsten Wiesel, and Robert Wright.

The themes of this book were first presented at forums whose hosts and audiences provided vital feedback. They include the Center for Bioethics at the University of Pennsylvania; the Cognition, Brain, and Art Symposium at the Getty Research Institute; the Developmental Behavior Genetics conference at the University of Pittsburgh; the Human Behavior and Evolution Society; the Humane Leadership Project at the University of Pennsylvania; the Institute on Race and Social Division at Boston University; the School of Humanities, Arts, and Social Sciences at MIT; the Neurosciences Research Program at the Neurosciences Institute; the Positive Psychology Summit; the Society for Evolutionary Analysis in Law; and the Tanner Lectures on Human Values at Yale University.

I am happy to acknowledge the superb environment for teaching and inquiry at the Massachusetts Institute of Technology, and the support of Mriganka Sur, head of the Department of Brain and Cognitive Sciences, Robert  {xiii}  Silbey, dean of the School of Science, Charles Vest, president of MIT, and many colleagues and students. John Bearley, the librarian of the Teuber Library, tracked down scholarly materials and answers to questions no matter how obscure. I also gratefully acknowledge the financial support of the MIT Mac Vicar Faculty Fellows program and the Peter de Florez chair. My research on language is supported by NIH Grant HD18381.

Wendy Wolf at Viking Penguin and Stefan McGrath at Penguin Books provided excellent advice and welcome good cheer. I thank them and my agents, John Brockman and Katinka Matson, for their efforts on behalf of the book. I am delighted that Katya Rice agreed to copy-edit this book, our fifth collaboration.

My heartfelt appreciation goes to my family, the Pinkers, Boodmans, and Subbiah-Adamses, for their love and support. Special thanks to my wife, Ilavenil Subbiah, for her wise advice and loving encouragement.

This book is dedicated to four people who have been dear friends and profound influences: Donald Symons, Judith Rich Harris, Leda Cosmides, and John Tooby.

CONTENTS

THE BLANK SLATE

THE BLANK SLATE, THE NOBLE
SAVAGE, AND THE GHOST
IN THE MACHINE

E

veryone has a theory of human nature. Everyone has to anticipate the behavior of others, and that means we all need theories about what makes people tick. A tacit theory of human nature — that behavior is caused by thoughts and feelings — is embedded in the very way we think about people. We fill out this theory by introspecting on our own minds and assuming that our fellows are like ourselves, and by watching people's behavior and filing away generalizations. We absorb still other ideas from our intellectual climate: from the expertise of authorities and the conventional wisdom of the day.

Our theory of human nature is the wellspring of much in our lives. We consult it when we want to persuade or threaten, inform or deceive. It advises us on how to nurture our marriages, bring up our children, and control our own behavior. Its assumptions about learning drive our educational policy; its assumptions about motivation drive our policies on economics, law, and crime. And because it delineates what people can achieve easily, what they can achieve only with sacrifice or pain, and what they cannot achieve at all, it affects our values: what we believe we can reasonably strive for as individuals and as a society. Rival theories of human nature are entwined in different ways of life and different political systems, and have been a source of much conflict over the course of history.

For millennia, the major theories of human nature have come from religion.¹ The Judeo-Christian tradition, for example, offers explanations for much of the subject matter now studied by biology and psychology. Humans are made in the image of God and are unrelated to animals.² Women are derivative of men and destined to be ruled by them.³ The mind is an immaterial substance: it has powers possessed by no purely physical structure, and can continue to exist when the body dies.⁴ The mind is made up of several components, including a moral sense, an ability to love, a capacity for reason that recognizes whether an act conforms to ideals of goodness, and a decision  {2}  faculty that chooses how to behave. Although the decision faculty is not bound by the laws of cause and effect, it has an innate tendency to choose sin. Our cognitive and perceptual faculties work accurately because God implanted ideals in them that correspond to reality and because he coordinates their functioning with the outside world. Mental health comes from recognizing God's purpose, choosing good and repenting sin, and loving God and one's fellow humans for God's sake.

The Judeo-Christian theory is based on events narrated in the Bible.. We know that the human mind has nothing in common with the minds of animals because the Bible says that humans were created separately. We know that the design of women is based on the design of men because in the second telling of the creation of women Eve was fashioned from the rib of Adam. Human decisions cannot be the inevitable effects of some cause, we may surmise, because God held Adam and Eve responsible for eating the fruit of the tree of knowledge, implying that they could have chosen otherwise. Women are dominated by men as punishment for Eve's disobedience, and men and women inherit the sinfulness of the first couple.

The Judeo-Christian conception is still the most popular theory of human nature in the United States. According to recent polls, 76 percent of Americans believe in the biblical account of creation, 79 percent believe that the miracles in the Bible actually took place, 76 percent believe in angels, the devil, and other immaterial souls, 67 percent believe they will exist in some form after their death, and only 15 percent believe that Darwin's theory of evolution is the best explanation for the origin of human life on Earth.⁵ Politicians on the right embrace the religious theory explicitly, and no mainstream politician would dare contradict it in public. But the modern sciences of cosmology, geology, biology, and archaeology have made it impossible for a scientifically literate person to believe that the biblical story of creation actually took place. As a result, the Judeo-Christian theory of human nature is no longer explicitly avowed by most academics, journalists, social analysts, and other intellectually engaged people.

Nonetheless, every society must operate with a theory of human nature, and our intellectual mainstream is committed to another one. The theory is seldom articulated or overtly embraced, but it lies at the heart of a vast number of beliefs and policies. Bertrand Russell wrote, “Every man, wherever he goes, is encompassed by a cloud of comforting convictions, which move with him like flies on a summer day.” For intellectuals today, many of those convictions are about psychology and social relations. I will refer to those convictions as the Blank Slate: the idea that the human mind has no inherent structure and can be inscribed at will by society or ourselves.

That theory of human nature — namely, that it barely exists — is the topic of this book. Just as religions contain a theory of human nature, so theories of  {3}  human nature take on some of the functions of religion, and the Blank Slate has become the secular religion of modern intellectual life. It is seen as a source of values, so the fact that it is based on a miracle — a complex mind arising out of nothing — is not held against it. Challenges to the doctrine from skeptics and scientists have plunged some believers into a crisis of faith and have led others to mount the kinds of bitter attacks ordinarily aimed at heretics and infidels. And just as many religious traditions eventually reconciled themselves to apparent threats from science (such as the revolutions of Copernicus and Darwin), so, I argue, will our values survive the demise of the Blank Slate.

The chapters in this part of the book (Part I) are about the ascendance of the Blank Slate in modern intellectual life, and about the new view of human nature and culture that is beginning to challenge it. In succeeding parts we will witness the anxiety evoked by this challenge (Part II) and see how the anxiety may be assuaged (Part III). Then I will show how a richer conception of human nature can provide insight into language, thought, social life, and morality (Part IV) and how it can clarify controversies on politics, violence, gender, childrearing, and the arts (Part V). Finally I will show how the passing of the Blank Slate is less disquieting, and in some ways less revolutionary, than it first appears (Part VI).

Chapter 1

The Official Theory

“Blank slate” is a loose translation of the medieval Latin term tabula rasa — literally, “scraped tablet.” It is commonly attributed to the philosopher John Locke (1632–1704), though in fact he used a different metaphor. Here is the famous passage from An Essay Concerning Human Understanding:

Let us then suppose the mind to be, as we say, white paper void of all characters, without any ideas. How comes it to be furnished? Whence comes it by that vast store which the busy and boundless fancy of man has painted on it with an almost endless variety? Whence has it all the materials of reason and knowledge? To this I answer, in one word, from EXPERIENCE.¹

Locke was taking aim at theories of innate ideas in which people were thought to be born with mathematical ideals, eternal truths, and a notion of God. His alternative theory, empiricism, was intended both as a theory of psychology — how the mind works — and as a theory of epistemology — how we come to know the truth. Both goals helped motivate his political philosophy, often honored as the foundation of liberal democracy. Locke opposed dogmatic justifications for the political status quo, such as the authority of the church and the divine right of kings, which had been touted as self-evident truths. He argued that social arrangements should be reasoned out from scratch and agreed upon by mutual consent, based on knowledge that any person could acquire. Since ideas are grounded in experience, which varies from person to person, differences of opinion arise not because one mind is equipped to grasp the truth and another is defective, but because the two minds have had different histories. Those differences therefore ought to be tolerated rather than suppressed. Locke's notion of a blank slate also undermined a hereditary royalty and aristocracy, whose members could claim no innate wisdom or merit if their minds had started out as blank as everyone else's. It also spoke against  {6}  the institution of slavery, because slaves could no longer be thought of as innately inferior or subservient.

During the past century the doctrine of the Blank Slate has set the agenda for much of the social sciences and humanities. As we shall see, psychology has sought to explain all thought, feeling, and behavior with a few simple mechanisms of learning. The social sciences have sought to explain all customs and social arrangements as a product of the socialization of children by the surrounding culture: a system of words, images, stereotypes, role models, and contingencies of reward and punishment. A long and growing list of concepts that would seem natural to the human way of thinking (emotions, kinship, the sexes, illness, nature, the world) are now said to have been “invented” or “socially constructed.”²

The Blank Slate has also served as a sacred scripture for political and ethical beliefs. According to the doctrine, any differences we see among races, ethnic groups, sexes, and individuals come not from differences in their innate constitution but from differences in their experiences. Change the experiences — by reforming parenting, education, the media, and social rewards — and you can change the person. Underachievement, poverty, and antisocial behavior can be ameliorated; indeed, it is irresponsible not to do so. And discrimination on the basis of purportedly inborn traits of a sex or ethnic group is simply irrational.

~

The Blank Slate is often accompanied by two other doctrines, which have also attained a sacred status in modern intellectual life. My label for the first of the two is commonly attributed to the philosopher Jean-Jacques Rousseau (1712–1778), though it really comes from John Dryden's The Conquest of Granada, published in 1670:

The concept of the noble savage was inspired by European colonists’ discovery of indigenous peoples in the Americas, Africa, and (later) Oceania. It captures the belief that humans in their natural state are selfless, peaceable, and untroubled, and that blights such as greed, anxiety, and violence are the products of civilization. In 1755 Rousseau wrote:

So many authors have hastily concluded that man is naturally cruel, and requires a regular system of police to be reclaimed; whereas nothing can be more gentle than him in his primitive state, when placed by nature at  {7}  an equal distance from the stupidity of brutes and the pernicious good sense of civilized man....

The more we reflect on this state, the more convinced we shall be that it was the least subject of any to revolutions, the best for man, and that nothing could have drawn him out of it but some fatal accident, which, for the public good, should never have happened. The example of the savages, most of whom have been found in this condition, seems to confirm that mankind was formed ever to remain in it, that this condition is the real youth of the world, and that all ulterior improvements have been so many steps, in appearance towards the perfection of individuals, but in fact towards the decrepitness of the species.³

First among the authors that Rousseau had in mind was Thomas Hobbes (1588–1679), who had presented a very different picture:

Hereby it is manifest, that during the time men live without a common power to keep them all in awe, they are in that condition which is called war; and such a war as is of every man against every man....

In such condition there is no place for industry, because the fruit thereof is uncertain: and consequently no culture of the earth; no navigation, nor use of the commodities that may be imported by sea; no commodious building; no instruments of moving and removing such things as require much force; no knowledge of the face of the earth; no account of time; no arts; no letters; no society; and which is worst of all, continual fear, and danger of violent death; and the life of man, solitary, poor, nasty, brutish, and short.⁴

Hobbes believed that people could escape this hellish existence only by surrendering their autonomy to a sovereign person or assembly. He called it a leviathan, the Hebrew word for a monstrous sea creature subdued by Yahweh at the dawn of creation.

Much depends on which of these armchair anthropologists is correct. If people are noble savages, then a domineering leviathan is unnecessary. Indeed, by forcing people to delineate private property for the state to recognize — property they might otherwise have shared — the leviathan creates the very greed and belligerence it is designed to control. A happy society would be our birthright; all we would need to do is eliminate the institutional barriers that keep it from us. If, in contrast, people are naturally nasty, the best we can hope for is an uneasy truce enforced by police and the army. The two theories have implications for private life as well. Every child is born a savage (that is, uncivilized), so if savages are naturally gentle, childrearing is a matter of providing  {8}  children with opportunities to develop their potential, and evil people are products of a society that has corrupted them. If savages are naturally nasty, then childrearing is an arena of discipline and conflict, and evil people are showing a dark side that was insufficiently tamed.

The actual writings of philosophers are always more complex than the theories they come to symbolize in the textbooks. In reality, the views of Hobbes and Rousseau are not that far apart. Rousseau, like Hobbes, believed (incorrectly) that savages were solitary, without ties of love or loyalty, and without any industry or art (and he may have out-Hobbes'd Hobbes in claiming they did not even have language). Hobbes envisioned — indeed, literally drew — his leviathan as an embodiment of the collective will, which was vested in it by a kind of social contract; Rousseau's most famous work is called The Social Contract, and in it he calls on people to subordinate their interests to a “general will.”

Nonetheless, Hobbes and Rousseau limned contrasting pictures of the state of nature that have inspired thinkers in the centuries since. No one can fail to recognize the influence of the doctrine of the Noble Savage in contemporary consciousness. We see it in the current respect for all things natural (natural foods, natural medicines, natural childbirth) and the distrust of the man-made, the unfashionability of authoritarian styles of childrearing and education, and the understanding of social problems as repairable defects in our institutions rather than as tragedies inherent to the human condition.

~

The other sacred doctrine that often accompanies the Blank Slate is usually attributed to the scientist, mathematician, and philosopher Rene Descartes (1596–1650):

There is a great difference between mind and body, inasmuch as body is by nature always divisible, and the mind is entirely indivisible.... When I consider the mind, that is to say, myself inasmuch as I am only a thinking being, I cannot distinguish in myself any parts, but apprehend myself to be clearly one and entire; and though the whole mind seems to be united to the whole body, yet if a foot, or an arm, or some other part, is separated from the body, I am aware that nothing has been taken from my mind. And the faculties of willing, feeling, conceiving, etc. cannot be properly speaking said to be its parts, for it is one and the same mind which employs itself in willing and in feeling and understanding. But it is quite otherwise with corporeal or extended objects, for there is not one of them imaginable by me which my mind cannot easily divide into parts.... This would be sufficient to teach me that the mind or soul of man is entirely different from the body, if I had not already been apprised of it on other grounds.⁵  {9} 

A memorable name for this doctrine was given three centuries later by a detractor, the philosopher Gilbert Ryle (1900–1976):

There is a doctrine about the nature and place of minds which is so prevalent among theorists and even among laymen that it deserves to be described as the official theory.... The official doctrine, which hails chiefly from Descartes, is something like this. With the doubtful exception of idiots and infants in arms every human being has both a body and a mind. Some would prefer to say that every human being is both a body and a mind. His body and his mind are ordinarily harnessed together, but after the death of the body his mind may continue to exist and function. Human bodies are in space and are subject to mechanical laws which govern all other bodies in space.... But minds are not in space, nor are their operations subject to mechanical laws....

... Such in outline is the official theory. I shall often speak of it, with deliberate abusiveness, as “the dogma of the Ghost in the Machine.”⁶

The Ghost in the Machine, like the Noble Savage, arose in part as a reaction to Hobbes. Hobbes had argued that life and mind could be explained in mechanical terms. Light sets our nerves and brain in motion, and that is what it means to see. The motions may persist like the wake of a ship or the vibration of a plucked string, and that is what it means to imagine. “Quantities” get added or subtracted in the brain, and that is what it means to think.

Descartes rejected the idea that the mind could operate by physical principles. He thought that behavior, especially speech, was not caused by anything, but freely chosen. He observed that our consciousness, unlike our bodies and other physical objects, does not feel as if it is divisible into parts or laid out in space. He noted that we cannot doubt the existence of our minds — indeed, we cannot doubt that we are our minds — because the very act of thinking presupposes that our minds exist. But we can doubt the existence of our bodies, because we can imagine ourselves to be immaterial spirits who merely dream or hallucinate that we are incarnate.

Descartes also found a moral bonus in his dualism (the belief that the mind is a different kind of thing from the body): “There is none which is more effectual in leading feeble spirits from the straight path of virtue, than to imagine that the soul of the brute is of the same nature as our own, and that in consequence, after this life we have nothing to fear or to hope for, any more than the flies and the ants.”⁷ Ryle explains Descartes's dilemma:

When Galileo showed that his methods of scientific discovery were competent to provide a mechanical theory which should cover every  {10}  occupant of space, Descartes found in himself two conflicting motives. As a man of scientific genius he could not but endorse the claims of mechanics, yet as a religious and moral man he could not accept, as Hobbes accepted, the discouraging rider to those claims, namely that human nature differs only in degree of complexity from clockwork.⁸

It can indeed be upsetting to think of ourselves as glorified gears and springs. Machines are insensate, built to be used, and disposable; humans are sentient, possessing of dignity and rights, and infinitely precious. A machine has some workaday purpose, such as grinding grain or sharpening pencils; a human being has higher purposes, such as love, worship, good works, and the creation of knowledge and beauty. The behavior of machines is determined by the ineluctable laws of physics and chemistry; the behavior of people is freely chosen. With choice comes freedom, and therefore optimism about our possibilities for the future. With choice also comes responsibility, which allows us to hold people accountable for their actions. And of course if the mind is separate from the body, it can continue to exist when the body breaks down, and our thoughts and pleasures will not someday be snuffed out forever.

As I mentioned, most Americans continue to believe in an immortal soul, made of some nonphysical substance, which can part company with the body. But even those who do not avow that belief in so many words still imagine that somehow there must be more to us than electrical and chemical activity in the brain. Choice, dignity, and responsibility are gifts that set off human beings from everything else in the universe, and seem incompatible with the idea that we are mere collections of molecules. Attempts to explain behavior in mechanistic terms are commonly denounced as “reductionist” or “determinist.” The denouncers rarely know exactly what they mean by those words, but everyone knows they refer to something bad. The dichotomy between mind and body also pervades everyday speech, as when we say “Use your head,” when we refer to “out-of-body experiences,” and when we speak of “John's body,” or for that matter “John's brain,” which presupposes an owner, John, that is somehow separate from the brain it owns. Journalists sometimes speculate about “brain transplants” when they really should be calling them “body transplants,” because, as the philosopher Dan Dennett has noted, this is the one transplant operation in which it is better to be the donor than the recipient.

The doctrines of the Blank Slate, the Noble Savage, and the Ghost in the Machine — or, as philosophers call them, empiricism, romanticism, and dualism — are logically independent, but in practice they are often found together. If the slate is blank, then strictly speaking it has neither injunctions to do good nor injunctions to do evil. But good and evil are asymmetrical: there are more ways to harm people than to help them, and harmful acts can hurt them to a  {11}  greater degree than virtuous acts can make them better off. So a blank slate, compared with one filled with motives, is bound to impress us more by its inability to do harm than by its inability to do good. Rousseau did not literally believe in a blank slate, but he did believe that bad behavior is a product of learning and socialization.⁹ “Men are wicked,” he wrote; “a sad and constant experience makes proof unnecessary.”¹⁰ But this wickedness comes from society: “There is no original perversity in the human heart. There is not a single vice to be found in it of which it cannot be said how and whence it entered.”¹¹ If the metaphors in everyday speech are a clue, then all of us, like Rousseau, associate blankness with virtue rather than with nothingness. Think of the moral connotations of the adjectives clean, fair, immaculate, lily-white, pure, spotless, unmarred, and unsullied, and of the nouns blemish, blot, mark, stain, and taint.

The Blank Slate naturally coexists with the Ghost in the Machine, too, since a slate that is blank is a hospitable place for a ghost to haunt. If a ghost is to be at the controls, the factory can ship the device with a minimum of parts. The ghost can read the body's display panels and pull its levers, with no need for a high-tech executive program, guidance system, or CPU. The more not-clockwork there is controlling behavior, the less clockwork we need to posit. For similar reasons, the Ghost in the Machine happily accompanies the Noble Savage. If the machine behaves ignobly, we can blame the ghost, which freely chose to carry out the iniquitous acts; we need not probe for a defect in the machine's design.

~

Philosophy today gets no respect. Many scientists use the term as a synonym for effete speculation. When my colleague Ned Block told his father that he would major in the subject, his father's reply was “Luft!” — Yiddish for “air.” And then there's the joke in which a young man told his mother he would become a Doctor of Philosophy and she said, “Wonderful! But what kind of disease is philosophy?”

But far from being idle or airy, the ideas of philosophers can have repercussions for centuries. The Blank Slate and its companion doctrines have infiltrated the conventional wisdom of our civilization and have repeatedly surfaced in unexpected places. William Godwin (1756–1835), one of the founders of liberal political philosophy, wrote that “children are a sort of raw material put into our hands,” their minds “like a sheet of white paper.”¹² More sinisterly, we find Mao Zedong justifying his radical social engineering by saying, “It is on a blank page that the most beautiful poems are written.”¹³ Even Walt Disney was inspired by the metaphor. “I think of a child's mind as a blank book,” he wrote. “During the first years of his life, much will be written on the pages. The quality of that writing will affect his life profoundly.”¹⁴  {12} 

Locke could not have imagined that his words would someday lead to Bambi (intended by Disney to teach self-reliance); nor could Rousseau have anticipated Pocahontas, the ultimate noble savage. Indeed, the soul of Rousseau seems to have been channeled by the writer of a recent Thanksgiving op-ed piece in the Boston Globe:

I would submit that the world native Americans knew was more stable, happier, and less barbaric than our society today.... there were no employment problems, community harmony was strong, substance abuse unknown, crime nearly nonexistent. What warfare there was between tribes was largely ritualistic and seldom resulted in indiscriminate or wholesale slaughter. While there were hard times, life was, for the most part, stable and predictable.... Because the native people respected what was around them, there was no loss of water or food resources because of pollution or extinction, no lack of materials for the daily essentials, such as baskets, canoes, shelter, or firewood.¹⁵

Not that there haven't been skeptics:

The third doctrine, too, continues to make its presence felt in modern times. In 2001 George W. Bush announced that the American government will not fund research on human embryonic stem cells if scientists have to destroy new embryos to extract them (the policy permits research on stem-cell lines that were previously extracted from embryos). He derived the policy after consulting not just with scientists but with philosophers and religious thinkers. Many of them framed the moral problem in terms of “ensoulment,” the moment at which the cluster of cells that will grow into a child is endowed with a soul. Some argued that ensoulment occurs at conception, which implies that the blastocyst (the five-day-old ball of cells from which stem cells are taken) is morally equivalent to a person and that destroying it is a form of murder.¹⁶ That argument proved decisive, which means that the  {13}  American policy on perhaps the most promising medical technology of the twenty-first century was decided by pondering the moral issue as it might have been framed centuries before: When does the ghost first enter the machine?

These are just a few of the fingerprints of the Blank Slate, the Noble Savage, and the Ghost in the Machine on modern intellectual life. In the following chapters we will see how the seemingly airy ideas of Enlightenment philosophers entrenched themselves in modern consciousness, and how recent discoveries are casting those ideas in doubt.

Chapter 2

Silly Putty

The Danish philologist Otto Jespersen (1860–1943) is one of history's most beloved linguists. His vivid books are still read today, especially Growth and Structure of the English Language, first published in 1905. Though Jespersen's scholarship is thoroughly modern, the opening pages remind us we are not reading a contemporary book:

There is one expression that continually comes to my mind whenever I think of the English language and compare it with others: it seems to be positively and expressly masculine, it is the language of a grown-up man and has very little childish or feminine about it....

To bring out one of these points I select at random, by way of contrast, a passage from the language of Hawaii: “I kona hiki ana aku ilaila ua hookipa ia mai la oia me ke aloha pumehana loa.” Thus it goes on, no single word ends in a consonant, and a group of two or more consonants is never found. Can any one be in doubt that even if such a language sounds pleasantly and be full of music and harmony the total impression is childlike and effeminate? You do not expect much vigor or energy in a people speaking such a language; it seems adapted only to inhabitants of sunny regions where the soil requires scarcely any labour on the part of man to yield him everything he wants, and where life therefore does not bear the stamp of a hard struggle against nature and fellow-creatures. In a lesser degree we find the same phonetic structure in such languages as Italian and Spanish; but how different are our Northern tongues.¹

And so he continues, advertising the virility, sobriety, and logic of English — and ends the chapter: “As the language is, so also is the nation.”

No modern reader can fail to be shocked by the sexism, racism, and chauvinism of the discussion: the implication that women are childlike, the  {15}  stereotyping of a colonized people as indolent, the gratuitous exalting of the author's own culture. Equally surprising are the sorry standards to which the great scholar here has sunk. The suggestion that a language can be “grown-up” and “masculine” is so subjective as to be meaningless. He attributes a personality trait to an entire people without any evidence, then advances two theories — that phonology reflects personality, and that warm climates breed laziness — without invoking even correlational data, let alone proof of causation. Even on his home ground the reasoning is flimsy. Languages with a consonant-vowel syllable structure like Hawaiian call for longer words to convey the same amount of information, hardly what you would expect in a people without “vigor or energy.” And the consonant-encrusted syllables of English are liable to be swallowed and misheard, hardly what you would expect from a logical, businesslike people.

But perhaps most disturbing is Jespersen's obliviousness to the possibility that he might be saying anything exceptionable. He took it for granted that his biases would be shared by his readers, whom he knew to be fellow men and speakers of “our” Northern tongues. “Can any one be in doubt?” he asked rhetorically; “you do not expect much vigor” from such a people, he asserted. The inferiority of women and other races needed neither justification nor apology.

I bring up Otto Jespersen, a man of his time, to show how standards have changed. The passage is a random sample of intellectual life a century ago; equally disturbing passages could have been taken from just about any writer of the nineteenth or early twentieth century.² It was a time of white men taking up the burden of leading their “new-caught sullen peoples, half-devil and half-child”; of shores teeming with huddled masses and wretched refuse; of European imperial powers looking (and sometimes throwing) daggers at one another. Imperialism, immigration, nationalism, and the legacy of slavery made differences between ethnic groups all too obvious. Some appeared educated and cultured, others ignorant and backward; some used fists and clubs to preserve their safety, others paid the police and the army to do it. It was tempting to assume that northern Europeans were an advanced race suited to rule the others. Just as convenient was the belief that women were constitutionally suited for the kitchen, church, and children, a belief supported by “research” showing that brainwork was bad for their physical and mental health.

Racial prejudice, too, had a scientific patina. Darwin's theory of evolution was commonly misinterpreted as an explanation of intellectual and moral progress rather than an explanation of how living things adapt to an ecological niche. The nonwhite races, it was easy to think, were rungs on an evolutionary ladder between the apes and the Europeans. Worse, Darwin's follower Herbert Spencer wrote that do-gooders would only interfere with the progress of evolution if they tried to improve the lot of the impoverished classes and  {16}  races, who were, in Spencer's view, biologically less fit. The doctrine of Social Darwinism (or, as it ought to be called, Social Spencerism, for Darwin wanted no part of it) attracted such unsurprising spokesmen as John D. Rockefeller and Andrew Carnegie.³ Darwin's cousin Francis Galton had suggested that human evolution should be given a helping hand by discouraging the less fit from breeding, a policy he called eugenics.⁴ Within a few decades laws were passed that called for the involuntary sterilization of delinquents and the “feebleminded” in Canada, the Scandinavian countries, thirty American states, and, ominously, Germany. The Nazis’ ideology of inferior races was later used to justify the murder of millions of Jews, Gypsies, and homosexuals.

We have come a long way. Though attitudes far worse than Jespersen's continue to thrive in much of the world and in parts of our society, they have been driven out of mainstream intellectual life in Western democracies. Today no respectable public figure in the United States, Britain, or Western Europe can casually insult women or sling around invidious stereotypes of other races or ethnic groups. Educated people try to be conscious of their hidden prejudices and to measure them against the facts and against the sensibilities of others. In public life we try to judge people as individuals, not as specimens of a sex or ethnic group. We try to distinguish might from right and our parochial tastes from objective merit, and therefore respect cultures that are different or poorer than ours. We realize that no mandarin is wise enough to be entrusted with directing the evolution of the species, and that it is wrong in any case for the government to interfere with such a personal decision as having a child. The very idea that the members of an ethnic group should be persecuted because of their biology fills us with revulsion.

These changes were cemented by the bitter lessons of lynchings, world wars, forced sterilizations, and the Holocaust, which showcased the grave implications of denigrating an ethnic group. But they emerged earlier in the twentieth century, the spinoff of an unplanned experiment: the massive immigration, social mobility, and diffusion of knowledge of the modern era. Most Victorian gentlemen could not have imagined that the coming century would see a nation-state forged by Jewish pioneers and soldiers, a wave of African American public intellectuals, or a software industry in Bangalore. Nor could they have anticipated that women would lead nations in wars, run huge corporations, or win Nobel Prizes in science. We now know that people of both sexes and all races are capable of attaining any station in life.

This sea change included a revolution in the treatment of human nature by scientists and scholars. Academics were swept along by the changing attitudes to race and sex, but they also helped to direct the tide by holding forth on human nature in books and magazines and by lending their expertise to government agencies. The prevailing theories of mind were refashioned to make racism and sexism as untenable as possible. The doctrine of the Blank  {17}  Slate became entrenched in intellectual life in a form that has been called the Standard Social Science Model or social constructionism.⁵ The model is now second nature to people and few are aware of the history behind it.⁶ Carl Degler, the foremost historian of this revolution, sums it up this way:

What the available evidence does seem to show is that ideology or a philosophical belief that the world could be a freer and more just place played a large part in the shift from biology to culture. Science, or at least certain scientific principles or innovative scholarship also played a role in the transformation, but only a limited one. The main impetus came from the will to establish a social order in which innate and immutable forces of biology played no role in accounting for the behavior of social groups.⁷

The takeover of intellectual life by the Blank Slate followed different paths in psychology and in the other social sciences, but they were propelled by the same historical events and progressive ideology. By the second and third decades of the twentieth century, stereotypes of women and ethnic groups were starting to look silly. Waves of immigrants from southern and eastern Europe, including many Jews, were filling the cities and climbing the social ladder. African Americans had taken advantage of the new “Negro colleges,” had migrated northward, and had begun the Harlem Renaissance. The graduates of flourishing women's colleges helped launch the first wave of feminism. For the first time not all professors and students were white Anglo-Saxon Protestant males. To say that this sliver of humanity was constitutionally superior had not only become offensive but went against what people could see with their own eyes. The social sciences in particular were attracting women, Jews, Asians, and African Americans, some of whom became influential thinkers.

Many of the pressing social problems of the first decades of the twentieth century concerned the less fortunate members of these groups. Should more immigrants be let in, and if so, from which countries? Once here, should they be encouraged to assimilate, and if so, how? Should women be given equal political rights and economic opportunities? Should blacks and whites be integrated? Other challenges were posed by children.⁸ Education had become compulsory and a responsibility of the state. As the cities teemed and family ties loosened, troubled and troublesome children became everyone's problem, and new institutions were invented to deal with them, such as kindergartens, orphanages, reform schools, fresh-air camps, humane societies, and boys’ and girls’ clubs. Child development was suddenly on the front burner. These social challenges were not going to go away, and the most humane assumption was that all human beings had an equal potential to prosper if they were given the  {18}  right upbringing and opportunities. Many social scientists saw it as their job to reinforce that assumption.

~

Modern psychological theory, as every introductory textbook makes clear, has roots in John Locke and other Enlightenment thinkers. For Locke the Blank Slate was a weapon against the church and tyrannical monarchs, but these threats had subsided in the English-speaking world by the nineteenth century. Locke's intellectual heir John Stuart Mill (1806–1873) was perhaps the first to apply his blank-slate psychology to political concerns we recognize today. He was an early supporter of women's suffrage, compulsory education, and the improvement of the conditions of the lower classes. This interacted with his stands in psychology and philosophy, as he explained in his autobiography:

I have long felt that the prevailing tendency to regard all the marked distinctions of human character as innate, and in the main indelible, and to ignore the irresistible proofs that by far the greater part of those differences, whether between individuals, races, or sexes, are such as not only might but naturally would be produced by differences in circumstances, is one of the chief hindrances to the rational treatment of great social questions, and one of the greatest stumbling blocks to human improvement. ... [This tendency is] so agreeable to human indolence, as well as to conservative interests generally, that unless attacked at the very root, it is sure to be carried to even a greater length than is really justified by the more moderate forms of intuitional philosophy.⁹

By “intuitional philosophy” Mill was referring to Continental intellectuals who maintained (among other things) that the categories of reason were innate. Mill wanted to attack their theory of psychology at the root to combat what he thought were its conservative social implications. He refined a theory of learning called associationism (previously formulated by Locke) that tried to explain human intelligence without granting it any innate organization. According to this theory, the blank slate is inscribed with sensations, which Locke called “ideas” and modern psychologists call “features.” Ideas that repeatedly appear in succession (such as the redness, roundness, and sweetness of an apple) become associated, so that any one of them can call to mind the others. And similar objects in the world activate overlapping sets of ideas in the mind. For example, after many dogs present themselves to the senses, the features that they share (fur, barking, four legs, and so on) hang together to stand for the category “dog.”

The associationism of Locke and Mill has been recognizable in  {19}  psychology ever since. It became the core of most models of learning, especially in the approach called behaviorism, which dominated psychology from the 1920s to the 1960s. The founder of behaviorism, John B. Watson (1878–1958), wrote one of the century's most famous pronouncements of the Blank Slate:

Give me a dozen healthy infants, well-formed, and my own specified world to bring them up in and I'll guarantee to take any one at random and train him to become any type of specialist I might select — doctor, lawyer, artist, merchant-chief, and yes, even beggar-man and thief, regardless of his talents, penchants, tendencies, abilities, vocations, and race of his ancestors.¹⁰

In behaviorism, an infant's talents and abilities didn't matter because there was no such thing as a talent or an ability. Watson had banned them from psychology, together with other contents of the mind, such as ideas, beliefs, desires, and feelings. They were subjective and unmeasurable, he said, and unfit for science, which studies only objective and measurable things. To a behaviorist, the only legitimate topic for psychology is overt behavior and how it is controlled by the present and past environment. (There is an old joke in psychology: What does a behaviorist say after making love? “It was good for you; how was it for me?”)

Locke's “ideas” had been replaced by “stimuli” and “responses,” but his laws of association survived as laws of conditioning. A response can be associated with a new stimulus, as when Watson presented a baby with a white rat and then clanged a hammer against an iron bar, allegedly making the baby associate fear with fur. And a response could be associated with a reward, as when a cat in a box eventually learned that pulling a string opened a door and allowed it to escape. In these cases an experimenter set up a contingency between a stimulus and another stimulus or between a response and a reward. In a natural environment, said the behaviorists, these contingencies are part of the causal texture of the world, and they inexorably shape the behavior of organisms, including humans.

Among the casualties of behaviorist minimalism was the rich psychology of William James (1842–1910). James had been inspired by Darwin's argument that perception, cognition, and emotion, like physical organs, had evolved as biological adaptations. James invoked the notion of instinct to explain the preferences of humans, not just those of animals, and he posited numerous mechanisms in his theory of mental life, including short-term and long-term memory. But with the advent of behaviorism they all joined the index of forbidden concepts. The psychologist J. R. Kantor wrote in 1923: “Brief is the answer to the question as to what is the relationship between  {20}  social psychology and instincts. Plainly, there is no relationship.”¹¹ Even sexual desire was redefined as a conditioned response. The psychologist Zing Yang Kuo wrote in 1929:

Behavior is not a manifestation of hereditary factors, nor can it be expressed in terms of heredity. [It is] a passive and forced movement mechanically and solely determined by the structural pattern of the organism and the nature of environmental forces.... All our sexual appetites are the result of social stimulation. The organism possesses no ready-made reaction to the other sex, any more than it possesses innate ideas.¹²

Behaviorists believed that behavior could be understood independently of the rest of biology, without attention to the genetic makeup of the animal or the evolutionary history of the species. Psychology came to consist of the study of learning in laboratory animals. B. E. Skinner (1904–1990), the most famous psychologist in the middle decades of the twentieth century, wrote a book called The Behavior of Organisms in which the only organisms were rats and pigeons and the only behavior was lever pressing and key pecking. It took a trip to the circus to remind psychologists that species and their instincts mattered after all. In an article called “The Misbehavior of Organisms,” Skinner's students Keller and Marian Breland reported that when they tried to use his techniques to train animals to insert poker chips into vending machines, the chickens pecked the chips, the raccoons washed them, and the pigs tried to root them with their snouts.¹³ And behaviorists were as hostile to the brain as they were to genetics. As late as 1974, Skinner wrote that studying the brain was just another misguided quest to find the causes of behavior inside the organism rather than out in the world.¹⁴

Behaviorism not only took over psychology but infiltrated the public consciousness. Watson wrote an influential childrearing manual recommending that parents establish rigid feeding schedules for their children and give them a minimum of attention and love. If you comfort a crying child, he wrote, you will reward him for crying and thereby increase the frequency of crying behavior. (Benjamin Spock's Baby and Child Care, first published in 1946 and famous for recommending indulgence toward children, was in part a reaction to Watson.) Skinner wrote several bestsellers arguing that harmful behavior is neither instinctive nor freely chosen but inadvertently conditioned. If we turned society into a big Skinner box and controlled behavior deliberately rather than haphazardly, we could eliminate aggression, overpopulation, crowding, pollution, and inequality, and thereby attain Utopia.¹⁵ The noble savage became the noble pigeon.  {21} 

Strict behaviorism is pretty much dead in psychology, but many of its attitudes live on. Associationism is the learning theory assumed by many mathematical models and neural network simulations of learning.¹⁶ Many neuroscientists equate learning with the forming of associations, and look for an associative bond in the physiology of neurons and synapses, ignoring other kinds of computation that might implement learning in the brain.¹⁷ (For example, storing the value of a variable in the brain, as in “x = 3,” is a critical computational step in navigating and foraging, which are highly developed talents of animals in the wild. But this kind of learning cannot be reduced to the formation of associations, and so it has been ignored in neuroscience.) Psychologists and neuroscientists still treat organisms interchangeably, seldom asking whether a convenient laboratory animal (a rat, a cat, a monkey) is like or unlike humans in crucial ways.¹⁸ Until recently, psychology ignored the content of beliefs and emotions and the possibility that the mind had evolved to treat biologically important categories in different ways.¹⁹ Theories of memory and reasoning didn't distinguish thoughts about people from thoughts about rocks or houses. Theories of emotion didn't distinguish fear from anger, jealousy, or love.²⁰ Theories of social relations didn't distinguish among family, friends, enemies, and strangers.²¹ Indeed, the topics in psychology that most interest laypeople — love, hate, work, play, food, sex, status, dominance, jealousy, friendship, religion, art — are almost completely absent from psychology textbooks.

One of the major documents of late twentieth-century psychology was the two-volume Parallel Distributed Processing by David Rumelhart, James McClelland, and their collaborators, which presented a style of neural network modeling called connectionism.²² Rumelhart and McClelland argued that generic associationist networks, subjected to massive amounts of training, could explain all of cognition. They realized that this theory left them without a good answer to the question “Why are people smarter than rats?” Here is their answer:

Given all of the above, the question does seem a bit puzzling.... People have much more cortex than rats do or even than other primates do; in particular they have very much more ... brain structure not dedicated to input/output — and presumably, this extra cortex is strategically placed in the brain to subserve just those functions that differentiate people from rats or even apes....

But there must be another aspect to the difference between rats and people as well. This is that the human environment includes other people and the cultural devices that they have developed to organize their thinking processes.²³  {22} 

Humans, then, are just rats with bigger blank slates, plus something called “cultural devices.” And that brings us to the other half of the twentieth-century revolution in social science.

~

He's so unhip, when you say “Dylan,”

He thinks you're talkin’ about Dylan Thomas (whoever he was).

The man ain't got no culture.

— Simon and Garfunkel

The word culture used to refer to exalted genres of entertainment, such as poetry, opera, and ballet. The other familiar sense — “the totality of socially transmitted behavior patterns, arts, beliefs, institutions, and all other products of human work and thought” — is only a century old. This change in the English language is just one of the legacies of the father of modern anthropology, Franz Boas (1858–1942).

The ideas of Boas, like the ideas of the major thinkers in psychology, were rooted in the empiricist philosophers of the Enlightenment, in this case George Berkeley (1685–1753). Berkeley formulated the theory of idealism, the notion that ideas, not bodies and other hunks of matter, are the ultimate constituents of reality. After twists and turns that are too convoluted to recount here, idealism became influential among nineteenth-century German thinkers. It was embraced by the young Boas, a German Jew from a secular, liberal family.

Idealism allowed Boas to lay a new intellectual foundation for egalitarianism. The differences among human races and ethnic groups, he proposed, come not from their physical constitution but from their culture, a system of ideas and values spread by language and other forms of social behavior. Peoples differ because their cultures differ. Indeed, that is how we should refer to them: the Eskimo culture or the Jewish culture, not the Eskimo race or the Jewish race. The idea that minds are shaped by culture served as a bulwark against racism and was the theory one ought to prefer on moral grounds. Boas wrote, “I claim that, unless the contrary can be proved, we must assume that all complex activities are socially determined, not hereditary.”²⁴

Boas's case was not just a moral injunction; it was rooted in real discoveries. Boas studied native peoples, immigrants, and children in orphanages to prove that all groups of humans had equal potential. Turning Jespersen on his head, Boas showed that the languages of primitive peoples were not simpler than those of Europeans; they were just different. Eskimos’ difficulty in discriminating the sounds of our language, for example, is matched by our difficulty in discriminating the sounds of theirs. True, many non-Western languages lack the means to express certain abstract concepts. They may have no words for numbers higher than three, for example, or no word for  {23}  goodness in general as opposed to the goodness of a particular person. But those limitations simply reflect the daily needs of those people as they live their lives, not an infirmity in their mental abilities. As in the story of Socrates drawing abstract philosophical concepts out of a slave boy, Boas showed that he could elicit new word forms for abstract concepts like “goodness” and “pity” out of a Kwakiutl native from the Pacific Northwest. He also observed that when native peoples come into contact with civilization and acquire things that have to be counted, they quickly adopt a full-blown counting system.²⁵

For all his emphasis on culture, Boas was not a relativist who believed that all cultures are equivalent, nor was he an empiricist who believed in the Blank Slate. He considered European civilization superior to tribal cultures, insisting only that all peoples were capable of achieving it. He did not deny that there might be a universal human nature, or that there might be differences among people within an ethnic group. What mattered to him was the idea that all ethnic groups are endowed with the same basic mental abilities.²⁶ Boas was right about this, and today it is accepted by virtually all scholars and scientists.

But Boas had created a monster. His students came to dominate American social science, and each generation outdid the previous one in its sweeping pronouncements. Boas's students insisted not just that differences among ethnic groups must be explained in terms of culture but that every aspect of human existence must be explained in terms of culture. For example, Boas had favored social explanations unless they were disproven, but his student Albert Kroeber favored them regardless of the evidence. “Heredity,” he wrote, “cannot be allowed to have acted any part in history.”²⁷ Instead, the chain of events shaping a people “involves the absolute conditioning of historical events by other historical events.”²⁸

Kroeber did not just deny that social behavior could be explained by innate properties of minds. He denied that it could be explained by any properties of minds. A culture, he wrote, is superorganic — it floats in its own universe, free of the flesh and blood of actual men and women: “Civilization is not mental action but a body or stream of products of mental exercise.... Mentality relates to the individual. The social or cultural, on the other hand, is in its essence non-individual. Civilization as such begins only where the individual ends.”²⁹

These two ideas — the denial of human nature, and the autonomy of culture from individual minds — were also articulated by the founder of sociology, Emile Durkheim (1858–1917), who had foreshadowed Kroeber's doctrine of the superorganic mind:

Every time that a social phenomenon is directly explained by a psychological phenomenon, we may be sure that the explanation is false.... The group thinks, feels, and acts quite differently from the way in which  {24}  members would were they isolated.... If we begin with the individual in seeking to explain phenomena, we shall be able to understand nothing of what takes place in the group.... Individual natures are merely the indeterminate material that the social factor molds and transforms. Their contribution consists exclusively in very general attitudes, in vague and consequently plastic predispositions.³⁰

And he laid down a law for the social sciences that would be cited often in the century to come: “The determining cause of a social fact should be sought among the social facts preceding it and not among the states of individual consciousness.”³¹

Both psychology and the other social sciences, then, denied that the minds of individual people were important, but they set out in different directions from there. Psychology banished mental entities like beliefs and desires altogether and replaced them with stimuli and responses. The other social sciences located beliefs and desires in cultures and societies rather than in the heads of individual people. The different social sciences also agreed that the contents of cognition — ideas, thoughts, plans, and so on — were really phenomena of language, overt behavior that anyone could hear and write down. (Watson proposed that “thinking” really consisted of teensy movements of the mouth and throat.) But most of all they shared a dislike of instincts and evolution. Prominent social scientists repeatedly declared the slate to be blank:

Instincts do not create customs; customs create instincts, for the putative instincts of human beings are always learned and never native.

— Ellsworth Faris (1927)³²

Cultural phenomena ... are in no respect hereditary but are characteristically and without exception acquired.

— George Murdock (1932)³³

Man has no nature; what he has is history.

— Jose Ortega y Gasset (1935)³⁴

With the exception of the instinctoid reactions in infants to sudden withdrawals of support and to sudden loud noises, the human being is entirely instinctless.... Man is man because he has no instincts, because everything he is and has become he has learned, acquired, from his culture, from the man-made part of the environment, from other human beings.

— Ashley Montagu (1973)³⁵  {25} 

True, the metaphor of choice was no longer a scraped tablet or white paper. Durkheim had spoken of “indeterminate material,” some kind of blob that was molded or pounded into shape by culture. Perhaps the best modern metaphor is Silly Putty, the rubbery stuff that children use both to copy printed matter (like a blank slate) and to mold into desired shapes (like indeterminate material). The malleability metaphor resurfaced in statements by two of Boas's most famous students:

Most people are shaped to the form of their culture because of the malleability of their original endowment.... The great mass of individuals take quite readily the form that is presented to them.

— Ruth Benedict (1934)³⁶

We are forced to conclude that human nature is almost unbelievably malleable, responding accurately and contrastingly to contrasting cul tural conditions.

— Margaret Mead (1935)³⁷

Others likened the mind to some kind of sieve:

Much of what is commonly called “human nature” is merely culture thrown against a screen of nerves, glands, sense organs, muscles, etc.

— Leslie White (1949)³⁸

Or to the raw materials for a factory:

Human nature is the rawest, most undifferentiated of raw material.

— Margaret Mead (1928)³⁹

Our ideas, our values, our acts, even our emotions, are, like our nervous system itself, cultural products — products manufactured, indeed, out of tendencies, capacities, and dispositions with which we were born, but manufactured nonetheless.

— Clifford Geertz (1973)⁴⁰

Or to an unprogrammed computer:

Man is the animal most desperately dependent upon such extragenetic, outside-the-skin control mechanisms, such cultural programs, for ordering his behavior.

— Clifford Geertz (1973)⁴¹  {26} 

Or to some other amorphous entity that can have many things done to it:

Cultural psychology is the study of the way cultural traditions and social practices regulate, express, transform, and permute the human psyche, resulting less in psychic unity for humankind than in ethnic divergences in mind, self and emotion.

— Richard Shweder (1990)⁴²

The superorganic or group mind also became an article of faith in social science. Robert Lowie (another Boas student) wrote, “The principles of psychology are as incapable of accounting for the phenomena of culture as is gravitation to account for architectural styles.”⁴³ And in case you missed its full implications, the anthropologist Leslie White spelled it out:

Instead of regarding the individual as a First Cause, as a prime mover, as the initiator and determinant of the culture process, we now see him as a component part, and a tiny and relatively insignificant part at that, of a vast, socio-cultural system that embraces innumerable individuals at any one time and extends back into their remote past as well.... For purposes of scientific interpretation, the culture process may be regarded as a thing sui generis; culture is explainable in terms of culture.⁴⁴

In other words, we should forget about the mind of an individual person like you, that tiny and insignificant part of a vast sociocultural system. The mind that counts is the one belonging to the group, which is capable of thinking, feeling, and acting on its own.

The doctrine of the superorganism has had an impact on modern life that extends well beyond the writings of social scientists. It underlies the tendency to reify “society” as a moral agent that can be blamed for sins as if it were a person. It drives identity politics, in which civil rights and political perquisites are allocated to groups rather than to individuals. And as we shall see in later chapters, it defined some of the great divides between major political systems in the twentieth century.

~

The Blank Slate was not the only part of the official theory that social scientists felt compelled to prop up. They also strove to consecrate the Noble Savage. Mead painted a Gauguinesque portrait of native peoples as peaceable, egalitarian, materially satisfied, and sexually unconnected. Her uplifting vision of who we used to be — and therefore who we can become again — was accepted by such otherwise skeptical writers as Bertrand Russell and H.L. Mencken. Ashley Montagu (also from the Boas circle), a prominent public intellectual from the 1950s until his recent death, tirelessly invoked the doctrine  {27}  of the Noble Savage to justify the quest for brotherhood and peace and to refute anyone who might think such efforts were futile. In 1950, for example, he drafted a manifesto for the newly formed UNESCO that declared, “Biological studies lend support to the ethic of universal brotherhood, for man is born with drives toward co-operation, and unless these drives are satisfied, men and nations alike fall ill.”⁴⁵ With the ashes of thirty-five million victims of World War II still warm or radioactive, a reasonable person might wonder how “biological studies” could show anything of the kind. The draft was rejected, but Montagu had better luck in the decades to come, when UNESCO and many scholarly societies adopted similar resolutions.⁴⁶

More generally, social scientists saw the malleability of humans and the autonomy of culture as doctrines that might bring about the age-old dream of perfecting mankind. We are not stuck with what we don't like about our current predicament, they argued. Nothing prevents us from changing it except a lack of will and the benighted belief that we are permanently consigned to it by biology. Many social scientists have expressed the hope of a new and improved human nature:

I felt (and said so early) that the environmental explanation was preferable, whenever justified by the data, because it was more optimistic, holding out the hope of improvement.

— Otto Klineberg (1928)⁴⁷

Modern sociology and modern anthropology are one in saying that the substance of culture, or civilization, is social tradition and that this social tradition is indefinitely modifiable by further learning on the part of men for happier and better ways of living together.... Thus the scientific study of institutions awakens faith in the possibility of remaking both human nature and human social life.

— Charles Ellwood (1922)⁴⁸

Barriers in many fields of knowledge are falling below the new optimism which is that anybody can learn anything.... We have turned away from the concept of human ability as something fixed in the physiological structure, to that of a flexible and versatile mechanism subject to great improvement.

— Robert Faris (1961)⁴⁹

Though psychology is not as politicized as some of the other social sciences, it too is sometimes driven by a Utopian vision in which changes in child-rearing and education will ameliorate social pathologies and improve human welfare. And psychological theorists sometimes try to add moral heft to arguments for connectionism or other empiricist theories with warnings about the  {28}  pessimistic implications of innatist theories. They argue, for example, that innatist theories open the door to inborn differences, which could foster racism, or that the theories imply that human traits are unchangeable, which could weaken support for social programs.⁵⁰

~

Twentieth-century social science embraced not just the Blank Slate and the Noble Savage but the third member of the trinity, the Ghost in the Machine. The declaration that we can change what we don't like about ourselves became a watchword of social science. But that only raises the question “Who or what is the ‘we'?” If the “we” doing the remaking are just other hunks of matter in the biological world, then any malleability of behavior we discover would be cold comfort, because we, the molders, would be biologically constrained and therefore might not mold people, or allow ourselves to be molded, in the most socially salutary way. A ghost in the machine is the ultimate liberator of human will — including the will to change society — from mechanical causation. The anthropologist Loren Eiseley made this clear when he wrote:

The mind of man, by indetermination, by the power of choice and cultural communication, is on the verge of escape from the blind control of that deterministic world with which the Darwinists had unconsciously shackled man. The inborn characteristics laid upon him by the biological extremists have crumbled away.... Wallace saw and saw correctly, that with the rise of man the evolution of parts was to a marked degree outmoded, that mind was now the arbiter of human destiny.⁵¹

The “Wallace” that Eiseley is referring to is Alfred Russel Wallace (1823–1913), the co-discoverer with Darwin of natural selection. Wallace parted company from Darwin by claiming that the human mind could not be explained by evolution and must have been designed by a superior intelligence. He certainly did believe that the mind of man could escape “the blind control of a deterministic world.” Wallace became a spiritualist and spent the later years of his career searching for a way to communicate with the souls of the dead.

The social scientists who believed in an absolute separation of culture from biology may not have literally believed in a spook haunting the brain. Some used the analogy of the difference between living and nonliving matter. Kroeber wrote: “The dawn of the social... is not a link in any chain, not a step in a path, but a leap to another plane.... [It is like] the first occurrence of life in the hitherto lifeless universe.... From this moment on there should be two worlds in place of one.”⁵² And Lowie insisted that it was “not mysticism, but sound scientific method” to say that culture was “sui generis” and could be explained only by culture, because everyone knows that in biology a living cell can come only from another living cell.⁵³  {29} 

At the time that Kroeber and Lowie wrote, they had biology on their side. Many biologists still thought that living things were animated by a special essence, an elan vital, and could not be reduced to inanimate matter. A 1931 history of biology, referring to genetics as it was then understood, said, “Thus the last of the biological theories leaves us where we first started, in the presence of a power called life or psyche which is not only of its own kind but unique in each and all of its exhibitions.”⁵⁴ In the next chapter we will see that the analogy between the autonomy of culture and the autonomy of life would prove to be more telling than these social scientists realized.

Chapter 3

The Last Wall to Fall

In 1755 Samuel Johnson wrote that his dictionary should not be expected to “change sublunary nature, and clear the world at once from folly, vanity, and affectation.” Few people today are familiar with the lovely word sublunary, literally “below the moon.” It alludes to the ancient belief in a strict division between the pristine, lawful, unchanging cosmos above and our grubby, chaotic, fickle Earth below. The division was already obsolete when Johnson used the word: Newton had shown that the same force that pulled an apple toward the ground kept the moon in its celestial orbit.

Newton's theory that a single set of laws governed the motions of all objects in the universe was the first event in one of the great developments in human understanding: the unification of knowledge, which the biologist E. O. Wilson has termed consilience.¹ Newton's breaching of the wall between the terrestrial and the celestial was followed by a collapse of the once equally firm (and now equally forgotten) wall between the creative past and the static present. That happened when Charles Lyell showed that the Earth was sculpted in the past by forces we see today (such as earthquakes and erosion) acting over immense spans of time.

The living and nonliving, too, no longer occupy different realms. In 1628 William Harvey showed that the human body is a machine that runs by hydraulics and other mechanical principles. In 1828 Friedrich Wohler showed that the stuff of life is not a magical, pulsating gel but ordinary compounds following the laws of chemistry. Charles Darwin showed how the astonishing diversity of life and its ubiquitous signs of design could arise from the physical process of natural selection among replicators. Gregor Mendel, and then James Watson and Francis Crick, showed how replication itself could be understood in physical terms.

The unification of our understanding of life with our understanding of matter and energy was the greatest scientific achievement of the second half of the twentieth century. One of its many consequences was to pull the rug out  {31}  from under social scientists like Kroeber and Lowie who had invoked the “sound scientific method” of placing the living and nonliving in parallel universes. We now know that cells did not always come from other cells and that the emergence of life did not create a second world where before there was just one. Cells evolved from simpler replicating molecules, a nonliving part of the physical world, and may be understood as collections of molecular machinery — fantastically complicated machinery, of course, but machinery nonetheless.

This leaves one wall standing in the landscape of knowledge, the one that twentieth-century social scientists guarded so jealously. It divides matter from mind, the material from the spiritual, the physical from the mental, biology from culture, nature from society, and the sciences from the social sciences, humanities, and arts. The division was built into each of the doctrines of the official theory: the blank slate given by biology versus the contents inscribed by experience and culture, the nobility of the savage in the state of nature versus the corruption of social institutions, the machine following inescapable laws versus the ghost that is free to choose and to improve the human condition.

But this wall, too, is falling. New ideas from four frontiers of knowledge — the sciences of mind, brain, genes, and evolution — are breaching the wall with a new understanding of human nature. In this chapter I will show how they are filling in the blank slate, declassing the noble savage, and exorcising the ghost in the machine. In the following chapter I will show that this new conception of human nature, connected to biology from below, can in turn be connected to the humanities and social sciences above. That new conception can give the phenomena of culture their due without segregating them into a parallel universe.

~

The first bridge between biology and culture is the science of mind, cognitive science.² The concept of mind has been perplexing for as long as people have reflected on their thoughts and feelings. The very idea has spawned paradoxes, superstitions, and bizarre theories in every period and culture. One can almost sympathize with the behaviorists and social constructionists of the first half of the twentieth century, who looked on minds as enigmas or conceptual traps that were best avoided in favor of overt behavior or the traits of a culture.

But beginning in the 1950s with the cognitive revolution, all that changed. It is now possible to make sense of mental processes and even to study them in the lab. And with a firmer grasp on the concept of mind, we can see that many tenets of the Blank Slate that once seemed appealing are now unnecessary or even incoherent. Here are five ideas from the cognitive revolution that have revamped how we think and talk about minds.

The first idea: The mental world can be grounded in the physical world by the concepts of information, computation, and feedback. A great divide between  {32}  mind and matter has always seemed natural because behavior appears to have a different kind of trigger than other physical events. Ordinary events have causes, it seems, but human behavior has reasons. I once participated in a BBC television debate on whether “science can explain human behavior.” Arguing against the resolution was a philosopher who asked how we might explain why someone was put in jail. Say it was for inciting racial hatred. The intention, the hatred, and even the prison, she said, cannot be described in the language of physics. There is simply no way to define “hatred” or “jail” in terms of the movements of particles. Explanations of behavior are like narratives, she argued, couched in the intentions of actors — a plane completely separate from natural science. Or take a simpler example. How might we explain why Rex just walked over to the phone? We would not say that phone-shaped stimuli caused Rex's limbs to swing in certain arcs. Rather, we might say that he wanted to speak to his friend Cecile and knew that Cecile was home. No explanation has as much predictive power as that one. If Rex was no longer on speaking terms with Cecile, or if he remembered that Cecile was out bowling that night, his body would not have risen off the couch.

For millennia the gap between physical events, on the one hand, and meaning, content, ideas, reasons, and intentions, on the other, seemed to cleave the universe in two. How can something as ethereal as “inciting hatred” or “wanting to speak to Cecile” actually cause matter to move in space? But the cognitive revolution unified the world of ideas with the world of matter using a powerful new theory: that mental life can be explained in terms of information, computation, and feedback. Beliefs and memories are collections of information — like facts in a database, but residing in patterns of activity and structure in the brain. Thinking and planning are systematic transformations of these patterns, like the operation of a computer program. Wanting and trying are feedback loops, like the principle behind a thermostat: they receive information about the discrepancy between a goal and the current state of the world, and then they execute operations that tend to reduce the difference. The mind is connected to the world by the sense organs, which transduce physical energy into data structures in the brain, and by motor programs, by which the brain controls the muscles.

This general idea may be called the computational theory of mind. It is not the same as the “computer metaphor” of the mind, the suggestion that the mind literally works like a human-made database, computer program, or thermostat. It says only that we can explain minds and human-made information processors using some of the same principles. It is just like other cases in which the natural world and human engineering overlap. A physiologist might invoke the same laws of optics to explain how the eye works and how a camera works without implying that the eye is like a camera in every detail.

The computational theory of mind does more than explain the existence  {33}  of knowing, thinking, and trying without invoking a ghost in the machine (though that would be enough of a feat). It also explains how those processes can be intelligent — how rationality can emerge from a mindless physical process. If a sequence of transformations of information stored in a hunk of matter (such as brain tissue or silicon) mirrors a sequence of deductions that obey the laws of logic, probability, or cause and effect in the world, they will generate correct predictions about the world. And making correct predictions in pursuit of a goal is a pretty good definition of “intelligence.”³

Of course there is no new thing under the sun, and the computational theory of mind was foreshadowed by Hobbes when he described mental activity as tiny motions and wrote that “reasoning is but reckoning.” Three and a half centuries later, science has caught up to his vision. Perception, memory, imagery, reasoning, decision making, language, and motor control are being studied in the lab and successfully modeled as computational paraphernalia such as rules, strings, matrices, pointers, lists, files, trees, arrays, loops, propositions, and networks. For example, cognitive psychologists are studying the graphics system in the head and thereby explaining how people “see” the solution to a problem in a mental image. They are studying the web of concepts in long-term memory and explaining why some facts are easier to recall than others. They are studying the processor and memory used by the language system to learn why some sentences are a pleasure to read and others a difficult slog.

And if the proof is in the computing, then the sister field of artificial intelligence is confirming that ordinary matter can perform feats that were supposedly performable by mental stuff alone. In the 1950s computers were already being called “electronic brains” because they could calculate sums, organize data, and prove theorems. Soon they could correct spelling, set type, solve equations, and simulate experts on restricted topics such as picking stocks and diagnosing diseases. For decades we psychologists preserved human bragging rights by telling our classes that no computer could read text, decipher speech, or recognize faces, but these boasts are obsolete. Today software that can recognize printed letters and spoken words comes packaged with home computers. Rudimentary programs that understand or translate sentences are available in many search engines and Help programs, and they are steadily improving. Face-recognition systems have advanced to the point that civil libertarians are concerned about possible abuse when they are used with security cameras in public places.

Human chauvinists can still write off these low-level feats. Sure, they say, the input and output processing can be fobbed off onto computational modules, but you still need a human user with the capacity for judgment, reflection, and creativity. But according to the computational theory of mind, these capacities are themselves forms of information processing and can be implemented in a computational system. In 1997 an IBM computer called Deep  {34}  Blue defeated the world chess champion Garry Kasparov, and unlike its predecessors, it did not just evaluate trillions of moves by brute force but was fitted with strategies that intelligently responded to patterns in the game. Newsweek called the match “The Brain's Last Stand.” Kasparov called the outcome “the end of mankind.”

You might still object that chess is an artificial world with discrete moves and a clear winner, perfectly suited to the rule-crunching of a computer. People, on the other hand, live in a messy world offering unlimited moves and nebulous goals. Surely this requires human creativity and intuition — which is why everyone knows that computers will never compose a symphony, write a story, or paint a picture. But everyone may be wrong. Recent artificial intelligence systems have written credible short stories,⁴ composed convincing Mozart-like symphonies,⁵ drawn appealing pictures of people and landscapes,⁶ and conceived clever ideas for advertisements.⁷

None of this is to say that the brain works like a digital computer, that artificial intelligence will ever duplicate the human mind, or that computers are conscious in the sense of having first-person subjective experience. But it does suggest that reasoning, intelligence, imagination, and creativity are forms of information processing, a well-understood physical process. Cognitive science, with the help of the computational theory of mind, has exorcised at least one ghost from the machine.

A second idea: The mind cannot be a blank slate, because blank slates don't do anything. As long as people had only the haziest concept of what a mind was or how it might work, the metaphor of a blank slate inscribed by the environment did not seem too outrageous. But as soon as one starts to think seriously about what kind of computation enables a system to see, think, speak, and plan, the problem with blank slates becomes all too obvious: they don't do anything. The inscriptions will sit there forever unless something notices patterns in them, combines them with patterns learned at other times, uses the combinations to scribble new thoughts onto the slate, and reads the results to guide behavior toward goals. Locke recognized this problem and alluded to something called “the understanding,” which looked at the inscriptions on the white paper and carried out the recognizing, reflecting, and associating. But of course explaining how the mind understands by invoking something called “the understanding” is circular.

This argument against the Blank Slate was stated pithily by Gottfried Wilhelm Leibniz (1646–1716) in a reply to Locke. Leibniz repeated the empiricist motto “There is nothing in the intellect that was not first in the senses,” then added, “except the intellect itself.”⁸ Something in the mind must be innate, if it is only the mechanisms that do the learning. Something has to see a world of objects rather than a kaleidoscope of shimmering pixels. Something has to infer the content of a sentence rather than parrot back the exact wording.  {35}  Something has to interpret other people's behavior as their attempts to achieve goals rather than as trajectories of jerking arms and legs.

In the spirit of Locke, one could attribute these feats to an abstract noun — perhaps not to “the understanding” but to “learning,” “intelligence,” “plasticity,” or “adaptiveness.” But as Leibniz remarked, to do so is to “ [save appearances] by fabricating faculties or occult qualities,... and fancying them to be like little demons or imps which can without ado perform whatever is wanted, as though pocket watches told the time by a certain horological faculty without needing wheels, or as though mills crushed grain by a fractive faculty without needing anything in the way of millstones.”⁹ Leibniz, like Hobbes (who had influenced him), was ahead of his time in recognizing that intelligence is a form of information processing and needs complex machinery to carry it out. As we now know, computers don't understand speech or recognize text as they roll off the assembly line; someone has to install the right software first. The same is likely to be true of the far more demanding performance of the human being. Cognitive modelers have found that mundane challenges like walking around furniture, understanding a sentence, recalling a fact, or guessing someone's intentions are formidable engineering problems that are at or beyond the frontiers of artificial intelligence. The suggestion that they can be solved by a lump of Silly Putty that is passively molded by something called “culture” just doesn't cut the mustard.

This is not to say that cognitive scientists have put the nature-nurture debate completely behind them; they are still spread out along a continuum of opinion on how much standard equipment comes with the human mind. At one end are the philosopher Jerry Fodor, who has suggested that all concepts might be innate (even “doorknob” and “tweezers”), and the linguist Noam Chomsky, who believes that the word “learning” is misleading and we should say that children “grow” language instead.¹⁰ At the other end are the connectionists, including Rumelhart, McClelland, Jeffrey Elman, and Elizabeth Bates, who build relatively simple computer models and train the living daylights out of them.¹¹ Fans locate the first extreme, which originated at the Massachusetts Institute of Technology, at the East Pole, the mythical place from which all directions are west. They locate the second extreme, which originated at the University of California, San Diego, at the West Pole, the mythical place from which all directions are east. (The names were suggested by Fodor during an MIT seminar at which he was fulminating against a “West Coast theorist” and someone pointed out that the theorist worked at Yale, which is, technically, on the East Coast.)¹²

But here is why the East Pole-West Pole debate is different from the ones that preoccupied philosophers for millennia: neither side believes in the Blank Slate. Everyone acknowledges that there can be no learning without innate circuitry to do the learning. In their West Pole manifesto Rethinking Innateness,  {36}  Bates and Elman and their coauthors cheerfully concede this point: “No learning rule can be entirely devoid of theoretical content nor can the tabula ever be completely rasa”¹³ They explain:

There is a widespread belief that connectionist models (and modelers) are committed to an extreme form of empiricism; and that any form of innate knowledge is to be avoided like the plague.... We obviously do not subscribe to this point of view.... There are good reasons to believe that some kinds of prior constraints [on learning models] are necessary. In fact, all connectionist models necessarily make some assumptions which must be regarded as constituting innate constraints.¹⁴

The disagreements between the two poles, though significant, are over the details: how many innate learning networks there are, and how specifically engineered they are for particular jobs. (We will explore some of these disagreements in Chapter 5.)

A third idea: An infinite range of behavior can be generated by finite combinatorial programs in the mind. Cognitive science has undermined the Blank Slate and the Ghost in the Machine in another way. People can be forgiven for scoffing at the suggestion that human behavior is “in the genes” or “a product of evolution” in the senses familiar from the animal world. Human acts are not selected from a repertoire of knee-jerk reactions like a fish attacking a red spot or a hen sitting on eggs. Instead, people may worship goddesses, auction kitsch on the Internet, play air guitar, fast to atone for past sins, build forts out of lawn chairs, and so on, seemingly without limit. A glance at National Geographic shows that even the strangest acts in our own culture do not exhaust what our species is capable of. If anything goes, one might think, then perhaps we are Silly Putty, or unconstrained agents, after all.

But that impression has been made obsolete by the computational approach to the mind, which was barely conceivable in the era in which the Blank Slate arose. The clearest example is the Chomskyan revolution in language.¹⁵ Language is the epitome of creative and variable behavior. Most utterances are brand-new combinations of words, never before uttered in the history of humankind. We are nothing like Tickle Me Elmo dolls who have a fixed list of verbal responses hard-wired in. But, Chomsky pointed out, for all its open-endedness language is not a free-for-all; it obeys rules and patterns. An English speaker can utter unprecedented strings of words such as Every day new universes come into existence, or He likes his toast with cream cheese and ketchup, or My car has been eaten by wolverines. But no one would say Car my been eaten has wolverines by or most of the other possible orderings of English words. Something in the head must be capable of generating not just any combinations of words but highly systematic ones.  {37} 

That something is a kind of software, a generative grammar that can crank out new arrangements of words. A battery of rules such as “An English sentence contains a subject and a predicate,” “A predicate contains a verb, an object, and a complement,” and “The subject of eat is the eater” can explain the boundless creativity of a human talker. With a few thousand nouns that can fill the subject slot and a few thousand verbs that can fill the predicate slot, one already has several million ways to open a sentence. The possible combinations quickly multiply out to unimaginably large numbers. Indeed, the repertoire of sentences is theoretically infinite, because the rules of language use a trick called recursion. A recursive rule allows a phrase to contain an example of itself, as in She thinks that he thinks that they think that he knows and so on, ad infinitum. And if the number of sentences is infinite, the number of possible thoughts and intentions is infinite too, because virtually every sentence expresses a different thought or intention. The combinatorial grammar for language meshes with other combinatorial programs in the head for thoughts and intentions. A fixed collection of machinery in the mind can generate an infinite range of behavior by the muscles.¹⁶

Once one starts to think about mental software instead of physical behavior, the radical differences among human cultures become far smaller, and that leads to a fourth new idea: Universal mental mechanisms can underlie superficial variation across cultures. Again, we can use language as a paradigm case of the open-endedness of behavior. Humans speak some six thousand mutually unintelligible languages. Nonetheless, the grammatical programs in their minds differ far less than the actual speech coming out of their mouths. We have known for a long time that all human languages can convey the same kinds of ideas. The Bible has been translated into hundreds of non-Western languages, and during World War II the U.S. Marine Corps conveyed secret messages across the Pacific by having Navajo Indians translate them to and from their native language. The fact that any language can be used to convey any proposition, from theological parables to military directives, suggests that all languages are cut from the same cloth.

Chomsky proposed that the generative grammars of individual languages are variations on a single pattern, which he called Universal Grammar. For example, in English the verb comes before the object (drink beer) and the preposition comes before the noun phrase (from the bottle). In Japanese the object comes before the verb (beer drink) and the noun phrase comes before the preposition, or, more accurately, the postposition (the bottle from). But it is a significant discovery that both languages have verbs, objects, and pre– or postpositions to start with, as opposed to having the countless other conceivable kinds of apparatus that could power a communication system. And it is even more significant that unrelated languages build their phrases by assembling a head (such as a verb or preposition) and a complement (such as a noun  {38}  phrase) and assigning a consistent order to the two. In English the head comes first; in Japanese the head comes last. But everything else about the structure of phrases in the two languages is pretty much the same. And so it goes with phrase after phrase and language after language. The common kinds of heads and complements can be ordered in 128 logically possible ways, but 95 percent of the world's languages use one of two: either the English ordering or its mirror image the Japanese ordering.¹⁷ A simple way to capture this uniformity is to say that all languages have the same grammar except for a parameter or switch that can be flipped to either the “head-first” or “head-last” setting. The linguist Mark Baker has recently summarized about a dozen of these parameters, which succinctly capture most of the known variation among the languages of the world.¹⁸

Distilling the variation from the universal patterns is not just a way to tidy up a set of messy data. It can also provide clues about the innate circuitry that makes learning possible. If the universal part of a rule is embodied in the neural circuitry that guides babies when they first learn language, it could explain how children learn language so easily and uniformly and without the benefit of instruction. Rather than treating the sound coming out of Mom's mouth as just an interesting noise to mimic verbatim or to slice and dice in arbitrary ways, the baby listens for heads and complements, pays attention to how they are ordered, and builds a grammatical system consistent with that ordering.

This idea can make sense of other kinds of variability across cultures. Many anthropologists sympathetic to social constructionism have claimed that emotions familiar to us, like anger, are absent from some cultures.¹⁹ (A few anthropologists say there are cultures with no emotions at all!)²⁰ For example, Catherine Lutz wrote that the Ifaluk (a Micronesian people) do not experience our “anger” but instead undergo an experience they call song. Song is a state of dudgeon triggered by a moral infraction such as breaking a taboo or acting in a cocky manner. It licenses one to shun, frown at, threaten, or gossip about the offender, though not to attack him physically. The target of song experiences another emotion allegedly unknown to Westerners: metagu, a state of dread that impels him to appease the song-ful one by apologizing, paying a fine, or offering a gift.

The philosophers Ron Mallon and Stephen Stich, inspired by Chomsky and other cognitive scientists, point out that the issue of whether to call Ifaluk song and Western anger the same emotion or different emotions is a quibble about the meaning of emotion words: whether they should be defined in terms of surface behavior or underlying mental computation.²¹ If an emotion is defined by behavior, then emotions certainly do differ across cultures. The Ifaluk react emotionally to a woman working in the taro gardens while menstruating or to a man entering a birthing house, and we do not. We react emotionally to someone shouting a racial epithet or raising the middle finger, but  {39}  as far as we know, the Ifaluk do not. But if an emotion is defined by mental mechanisms — what psychologists like Paul Ekman and Richard Lazarus call “affect programs” or “if–then formulas” (note the computational vocabulary) — we and the Ifaluk are not so different after all.²² We might all be equipped with a program that responds to an affront to our interests or our dignity with an unpleasant burning feeling that motivates us to punish or to exact compensation. But what counts as an affront, whether we feel it is permissible to glower in a particular setting, and what kinds of retribution we think we are entitled to, depend on our culture. The stimuli and responses may differ, but the mental states are the same, whether or not they are perfectly labeled by words in our language.

And as in the case of language, without some innate mechanism for mental computation, there would be no way to learn the parts of a culture that do have to be learned. It is no coincidence that the situations that provoke song among the Ifaluk include violating a taboo, being lazy or disrespectful, and refusing to share, but do not include respecting a taboo, being kind and deferential, and standing on one's head. The Ifaluk construe the first three as similar because they evoke the same affect program — they are perceived as affronts. That makes it easier to learn that they call for the same reaction and makes it more likely that those three would be lumped together as the acceptable triggers for a single emotion.

The moral, then, is that familiar categories of behavior — marriage customs, food taboos, folk superstitions, and so on — certainly do vary across cultures and have to be learned, but the deeper mechanisms of mental computation that generate them may be universal and innate. People may dress differently, but they may all strive to flaunt their status via their appearance. They may respect the rights of the members of their clan exclusively or they may extend that respect to everyone in their tribe, nation-state, or species, but all divide the world into an in-group and an out-group. They may differ in which outcomes they attribute to the intentions of conscious beings, some allowing only that artifacts are deliberately crafted, others believing that illnesses come from magical spells cast by enemies, still others believing that the entire world was brought into being by a creator. But all of them explain certain events by invoking the existence of entities with minds that strive to bring about goals. The behaviorists got it backwards: it is the mind, not behavior, that is lawful.

A fifth idea: The mind is a complex system composed of many interacting parts. The psychologists who study emotions in different cultures have made another important discovery. Candid facial expressions appear to be the same everywhere, but people in some cultures learn to keep a poker face in polite company.²³ A simple explanation is that the affect programs fire up facial expressions in the same way in all people, but a separate system of “display rules” governs when they can be shown.  {40} 

The difference between these two mechanisms underscores another insight of the cognitive revolution. Before the revolution, commentators invoked enormous black boxes such as “the intellect” or “the understanding,” and they made sweeping pronouncements about human nature, such as that we are essentially noble or essentially nasty. But we now know that the mind is not a homogeneous orb invested with unitary powers or across-the-board traits. The mind is modular, with many parts cooperating to generate a train of thought or an organized action. It has distinct information-processing systems for filtering out distractions, learning skills, controlling the body, remembering facts, holding information temporarily, and storing and executing rules. Cutting across these data-processing systems are mental faculties (sometimes called multiple intelligences) dedicated to different kinds of content, such as language, number, space, tools, and living things. Cognitive scientists at the East Pole suspect that the content-based modules are differentiated largely by the genes;²⁴ those at the West Pole suspect they begin as small innate biases in attention and then coagulate out of statistical patterns in the sensory input.²⁵ But those at both poles agree that the brain is not a uniform meatloaf. Still another layer of information-processing systems can be found in the affect programs, that is, the systems for motivation and emotion.

The upshot is that an urge or habit coming out of one module can be translated into behavior in different ways — or suppressed altogether — by some other module. To take a simple example, cognitive psychologists believe that a module called the “habit system” underlies our tendency to produce certain responses habitually, such as responding to a printed word by pronouncing it silently. But another module, called the “supervisory attention system,” can override it and focus on the information relevant to a stated problem, such as naming the color of the ink the word is printed in, or thinking up an action that goes with the word.²⁶ More generally, the interplay of mental systems can explain how people can entertain revenge fantasies that they never act on, or can commit adultery only in their hearts. In this way the theory of human nature coming out of the cognitive revolution has more in common with the Judeo-Christian theory of human nature, and with the psychoanalytic theory proposed by Sigmund Freud, than with behaviorism, social constructionism, and other versions of the Blank Slate. Behavior is not just emitted or elicited, nor does it come directly out of culture or society. It comes from an internal struggle among mental modules with differing agendas and goals.

The idea from the cognitive revolution that the mind is a system of universal, generative computational modules obliterates the way that debates on human nature have been framed for centuries. It is now simply misguided to ask whether humans are flexible or programmed, whether behavior is universal or varies across cultures, whether acts are learned or innate, whether we are essentially good or essentially evil. Humans behave flexibly because they are  {41}  programmed: their minds are packed with combinatorial software that can generate an unlimited set of thoughts and behavior. Behavior may vary across cultures, but the design of the mental programs that generate it need not vary. Intelligent behavior is learned successfully because we have innate systems that do the learning. And all people may have good and evil motives, but not everyone may translate them into behavior in the same way.

~

The second bridge between mind and matter is neuroscience, especially cognitive neuroscience, the study of how cognition and emotion are implemented in the brain.²⁷ Francis Crick wrote a book about the brain called The Astonishing Hypothesis, alluding to the idea that all our thoughts and feelings, joys and aches, dreams and wishes consist in the physiological activity of the brain.²⁸ Jaded neuroscientists, who take the idea for granted, snickered at the title, but Crick was right: the hypothesis is astonishing to most people the first time they stop to ponder it. Who cannot sympathize with the imprisoned Dmitri Karamazov as he tries to make sense of what he has just learned from a visiting academic?

Imagine: inside, in the nerves, in the head — that is, these nerves are there in the brain ... (damn them!) there are sort of little tails, the little tails of those nerves, and as soon as they begin quivering ... that is, you see, I look at something with my eyes and then they begin quivering, those little tails ... and when they quiver, then an image appears ... it doesn't appear at once, but an instant, a second, passes ... and then something like a moment appears; that is, not a moment — devil take the moment! — but an image; that is, an object, or an action, damn it! That's why I see and then think, because of those tails, not at all because I've got a soul, and that I am some sort of image and likeness. All that is nonsense! Rakitin explained it all to me yesterday, brother, and it simply bowled me over. It's magnificent, Alyosha, this science! A new man's arising — that I understand.... And yet I am sorry to lose God!²⁹

Dostoevsky's prescience is itself astonishing, because in 1880 only the rudiments of neural functioning were understood, and a reasonable person could have doubted that all experience arises from quivering nerve tails. But no longer. One can say that the information-processing activity of the brain causes the mind, or one can say that it is the mind, but in either case the evidence is overwhelming that every aspect of our mental lives depends entirely on physiological events in the tissues of the brain.

When a surgeon sends an electrical current into the brain, the person can have a vivid, lifelike experience. When chemicals seep into the brain, they can alter the person's perception, mood, personality, and reasoning. When a patch  {42}  of brain tissue dies, a part of the mind can disappear: a neurological patient may lose the ability to name tools, recognize faces, anticipate the outcome of his behavior, empathize with others, or keep in mind a region of space or of his own body. (Descartes was thus wrong when he said that “the mind is entirely indivisible” and concluded that it must be completely different from the body.) Every emotion and thought gives off physical signals, and the new technologies for detecting them are so accurate that they can literally read a person's mind and tell a cognitive neuroscientist whether the person is imagining a face or a place. Neuroscientists can knock a gene out of a mouse (a gene also found in humans) and prevent the mouse from learning, or insert extra copies and make the mouse learn faster. Under the microscope, brain tissue shows a staggering complexity — a hundred billion neurons connected by a hundred trillion synapses — that is commensurate with the staggering complexity of human thought and experience. Neural network modelers have begun to show how the building blocks of mental computation, such as storing and retrieving a pattern, can be implemented in neural circuitry. And when the brain dies, the person goes out of existence. Despite concerted efforts by Alfred Russel Wallace and other Victorian scientists, it is apparently not possible to communicate with the dead.

Educated people, of course, know that perception, cognition, language, and emotion are rooted in the brain. But it is still tempting to think of the brain as it was shown in old educational cartoons, as a control panel with gauges and levers operated by a user — the self, the soul, the ghost, the person, the “me.” But cognitive neuroscience is showing that the self, too, is just another network of brain systems.

The first hint came from Phineas Gage, the nineteenth-century railroad worker familiar to generations of psychology students. Gage was using a yard-long spike to tamp explosive powder into a hole in a rock when a spark ignited the powder and sent the spike into his cheekbone, through his brain, and out the top of his skull. Phineas survived with his perception, memory, language, and motor functions intact. But in the famous understatement of a co-worker, “Gage was no longer Gage.” A piece of iron had literally turned him into a different person, from courteous, responsible, and ambitious to rude, unreliable, and shiftless. It did this by impaling his ventromedial prefrontal cortex, the region of the brain above the eyes now known to be involved in reasoning about other people. Together with other areas of the prefrontal lobes and the limbic system (the seat of the emotions), it anticipates the consequences of one's actions and selects behavior consonant with one's goals.³⁰

Cognitive neuroscientists have not only exorcised the ghost but have shown that the brain does not even have a part that does exactly what the ghost is supposed to do: review all the facts and make a decision for the rest of the brain to carry out.³¹ Each of us feels that there is a single “I” in control. But that  {43}  is an illusion that the brain works hard to produce, like the impression that our visual fields are rich in detail from edge to edge. (In fact, we are blind to detail outside the fixation point. We quickly move our eyes to whatever looks interesting, and that fools us into thinking that the detail was there all along.) The rain does have supervisory systems in the prefrontal lobes and anterior cingulate cortex, which can push the buttons of behavior and override habits and urges. But those systems are gadgets with specific quirks and limitations; they are not implementations of the rational free agent traditionally identified with the soul or the self.

One of the most dramatic demonstrations of the illusion of the unified self comes from the neuroscientists Michael Gazzaniga and Roger Sperry, who showed that when surgeons cut the corpus callosum joining the cerebral hemispheres, they literally cut the self in two, and each hemisphere can exercise free will without the other one's advice or consent. Even more disconcertingly, the left hemisphere constantly weaves a coherent but false account of the behavior chosen without its knowledge by the right. For example, if an experimenter flashes the command “WALK” to the right hemisphere (by keeping it in the part of the visual field that only the right hemisphere can see), the person will comply with the request and begin to walk out of the room. But when the person (specifically, the person's left hemisphere) is asked why he just got up, he will say, in all sincerity, “To get a Coke” — rather than “I don't really know” or “The urge just came over me” or “You've been testing me for years since I had the surgery, and sometimes you get me to do things but I don't know exactly what you asked me to do.” Similarly, if the patient's left hemisphere is shown a chicken and his right hemisphere is shown a snowfall, and both hemispheres have to select a picture that goes with what they see (each using a different hand), the left hemisphere picks a claw (correctly) and the right picks a shovel (also correctly). But when the left hemisphere is asked why the whole person made those choices, it blithely says, “Oh, that's simple. The chicken claw goes with the chicken, and you need a shovel to clean out the chicken shed.”³²

The spooky part is that we have no reason to think that the baloney-generator in the patient's left hemisphere is behaving any differently from ours as we make sense of the inclinations emanating from the rest of our brains. The conscious mind — the self or soul — is a spin doctor, not the commander in chief. Sigmund Freud immodestly wrote that “humanity has in the course of time had to endure from the hands of science three great outrages upon its naïve self-love”: the discovery that our world is not the center of the celestial spheres but rather a speck in a vast universe, the discovery that we were not specially created but instead descended from animals, and the discovery that often our conscious minds do not control how we act but merely tell us a story about our actions. He was right about the cumulative impact, but it was  {44}  cognitive neuroscience rather than psychoanalysis that conclusively delivered the third blow.

Cognitive neuroscience is undermining not just the Ghost in the Machine but also the Noble Savage. Damage to the frontal lobes does not only dull the person or subtract from his behavioral repertoire but can unleash aggressive attacks.³³ That happens because the damaged lobes no longer serve as inhibitory brakes on parts of the limbic system, particularly a circuit that links the amygdala to the hypothalamus via a pathway called the stria terminalis. Connections between the frontal lobe in each hemisphere and the limbic system provide a lever by which a person's knowledge and goals can override other mechanisms, and among those mechanisms appears to be one designed to generate behavior that harms other people.³⁴

Nor is the physical structure of the brain a blank slate. In the mid-nineteenth century the neurologist Paul Broca discovered that the folds and wrinkles of the cerebral cortex do not squiggle randomly like fingerprints but have a recognizable geometry. Indeed, the arrangement is so consistent from brain to brain that each fold and wrinkle can be given a name. Since that time neuroscientists have discovered that the gross anatomy of the brain — the sizes, shapes, and connectivity of its lobes and nuclei, and the basic plan of the cerebral cortex — is largely shaped by the genes in normal prenatal development.³⁵ So is the quantity of gray matter in the different regions of the brains of different people, including the regions that underlie language and reasoning.³⁶

This innate geometry and cabling can have real consequences for thinking, feeling, and behavior. As we shall see in a later chapter, babies who suffer damage to particular areas of the brain often grow up with permanent deficits in particular mental faculties. And people born with variations on the typical plan have variations in the way their minds work. According to a recent study of the brains of identical and fraternal twins, differences in the amount of gray matter in the frontal lobes are not only genetically influenced but are significantly correlated with differences in intelligence.³⁷ A study of Albert Einstein's brain revealed that he had large, unusually shaped inferior parietal lobules, which participate in spatial reasoning and intuitions about number.³⁸ Gay men are likely to have a smaller third interstitial nucleus in the anterior hypothalamus, a nucleus known to have a role in sex differences.³⁹ And convicted murderers and other violent, antisocial people are likely to have a smaller and less active prefrontal cortex, the part of the brain that governs decision making and inhibits impulses.⁴⁰ These gross features of the brain are almost certainly not sculpted by information coming in from the senses, which implies that differences in intelligence, scientific genius, sexual orientation, and impulsive violence are not entirely learned.

Indeed, until recently the innateness of brain structure was an embarrassment  {45}  for neuroscience. The brain could not possibly be wired by the genes down to the last synapse, because there isn't nearly enough information in the genome to do so. And we know that people learn throughout their lives, and products of that learning have to be stored in the brain somehow. Unless you believe in a ghost in the machine, everything a person learns has to affect some part of the brain; more accurately, learning is a change in some part of the brain. But it was difficult to find the features of the brain that reflected those changes amid all that innate structure. Becoming stronger in math or motor coordination or visual discrimination does not bulk up the brain the way becoming stronger at weightlifting bulks up the muscles.

Now, at last, neuroscience is beginning to catch up with psychology by discovering changes in the brain that underlie learning. As we shall see, the boundaries between swatches of cortex devoted to different body parts, talents, and even physical senses can be adjusted by learning and practice. Some neuroscientists are so excited by these discoveries that they are trying to push the pendulum in the other direction, emphasizing the plasticity of the cerebral cortex. But for reasons that I will review in Chapter 5, most neuroscientists believe that these changes take place within a matrix of genetically organized structure. There is much we don't understand about how the brain is laid out in development, but we know that it is not indefinitely malleable by experience.

~

THE THIRD BRIDGE between the biological and the mental is behavioral genetics, the study of how genes affect behavior.⁴¹ All the potential for thinking, learning, and feeling that distinguishes humans from other animals lies in the information contained in the DNA of the fertilized ovum. This is most obvious when we compare species. Chimpanzees brought up in a human home do not speak, think, or act like people, and that is because of the information in the ten megabytes of DNA that differ between us. Even the two species of chimpanzees, common chimps and bonobos, which differ in just a few tenths of one percent of their genomes, part company in their behavior, as zookeepers first discovered when they inadvertently mixed the two. Common chimps are among the most aggressive mammals known to zoology, bonobos among the most peaceable; in common chimps the males dominate the females, in bonobos the females have the upper hand; common chimps have sex for procreation, bonobos for recreation. Small differences in the genes can lead to large differences in behavior. They can affect the size and shape of the different parts of the brain, their wiring, and the nanotechnology that releases, binds, and recycles hormones and neurotransmitters.

The importance of genes in organizing the normal brain is underscored by the many ways in which nonstandard genes can give rise to nonstandard minds. When I was an undergraduate an exam question in Abnormal Psychology asked, “What is the best predictor that a person will become schizophrenic?”  {46}  The answer was, “Having an identical twin who is schizophrenic.” At the time it was a trick question, because the reigning theories of schizophrenia pointed to societal stress, “schizophrenogenic mothers,” double binds, and other life experiences (none of which turned out to have much, if any, importance); hardly anyone thought about genes as a possible cause. But even then the evidence was there: schizophrenia is highly concordant within pairs of identical twins, who share all their DNA and most of their environment, but far less concordant within pairs of fraternal twins, who share only half their DNA (of the DNA that varies in the population) and most of their environment. The trick question could be asked — and would have the same answer — for virtually every cognitive and emotional disorder or difference ever observed. Autism, dyslexia, language delay, language impairment, learning disability, left-handedness, major depressions, bipolar illness, obsessive-compulsive disorder, sexual orientation, and many other conditions run in families, are more concordant in identical than in fraternal twins, are better predicted by people's biological relatives than by their adoptive relatives, and are poorly predicted by any measurable feature of the environment.⁴²

Genes not only push us toward exceptional conditions of mental functioning but scatter us within the normal range, producing much of the variation in ability and temperament that we notice in the people around us. The famous Chas Addams cartoon from The New Yorker is only a slight exaggeration:

© The New Yorker Collection 1981. Charles Addams from cartoonbank.com. All rights reserved.  {47}

Identical twins think and feel in such similar ways that they sometimes suspect they are linked by telepathy. When separated at birth and reunited as adults they say they feel they have known each other all their lives. Testing confirms that identical twins, whether separated at birth or not, are eerily alike (though far from identical) in just about any trait one can measure. They are similar in verbal, mathematical, and general intelligence, in their degree of life satisfaction, and in personality traits such as introversion, agreeableness, neucriticism, conscientiousness, and openness to experience. They have similar attitudes toward controversial issues such as the death penalty, religion, and modern music. They resemble each other not just in paper-and-pencil tests but in consequential behavior such as gambling, divorcing, committing crimes, getting into accidents, and watching television. And they boast dozens of shared idiosyncrasies such as giggling incessantly, giving interminable answers to simple questions, dipping buttered toast in coffee, and — in the case of Abigail van Buren and Ann Landers — writing indistinguishable syndicated advice columns. The crags and valleys of their electroencephalograms (brainwaves) are as alike as those of a single person recorded on two occasions, and the wrinkles of their brains and distribution of gray matter across cortical areas are also similar.⁴³

The effects of differences in genes on differences in minds can be measured, and the same rough estimate — substantially greater than zero, but substantially less than 100 percent — pops out of the data no matter what measuring stick is used. Identical twins are far more similar than fraternal twins, whether they are raised apart or together; identical twins raised apart are highly similar; biological siblings, whether raised together or apart, are far more similar than adoptive siblings. Many of these conclusions come from massive studies in Scandinavian countries where governments keep huge databases on their citizens, and they employ the best-validated measuring instruments known to psychology. Skeptics have offered alternative explanations that try to push the effects of the genes to zero — they suggest that identical twins separated at birth may have been placed in similar adoptive homes, that they may have contacted each other before being tested, that they look alike and hence may have been treated alike, and that they shared a womb in addition to their genes. But as we shall see in the chapter on children, these explanations have all been tested and rejected. Recently a new kind of evidence may be piled on the heap. “Virtual twins” are the mirror image of identical twins raised apart: they are unrelated siblings, one or both adopted, who are raised together from infancy. Though they are the same age and are growing up in the same family, the psychologist Nancy Segal found that their IQ scores are barely correlated.⁴⁴ One father in the study said that despite efforts to treat them alike, the virtual twins are “like night and day.”

Twinning and adoption are natural experiments that offer strong indirect  {48}  evidence that differences in minds can come from differences in genes. Recently geneticists have pinpointed some of the genes that can cause the differences. A single wayward nucleotide in a gene called FOXP2 causes a hereditary disorder in speech and language.⁴⁵ A gene on the same chromosome, LIM-kinasel, produces a protein found in growing neurons that helps install the faculty of spatial cognition: when the gene is deleted, the person has normal intelligence but cannot assemble objects, arrange blocks, or copy shapes.⁴⁶ One version of the gene IGF2R is associated with high general intelligence, accounting for as many as four IQ points and two percent of the variation in intelligence among normal individuals.⁴⁷ If you have a longer than average version of the D4DR dopamine receptor gene, you are more likely to be a thrill seeker, the kind of person who jumps out of airplanes, clambers up frozen waterfalls, or has sex with strangers.⁴⁸ If you have a shorter version of a stretch of DNA that inhibits the serotonin transporter gene on chromosome 17, you are more likely to be neurotic and anxious, the kind of person who can barely function at social gatherings for fear of offending someone or acting like a fool.⁴⁹

Single genes with large consequences are the most dramatic examples of the effects of genes on the mind, but they are not the most representative examples. Most psychological traits are the product of many genes with small effects that are modulated by the presence of other genes, rather than the product of a single gene with a large effect that shows up come what may. That is why studies of identical twins (two people who share all their genes) consistently show powerful genetic effects on a trait even when the search for a single gene for that trait is unsuccessful.

In 2001 the complete sequence of the human genome was published, and with it came a powerful new ability to identify genes and their products, including those that are active in the brain. In the coming decade, geneticists will identify genes that differentiate us from chimpanzees, infer which of them were subject to natural selection during the millions of years our ancestors evolved into humans, identify which combinations are associated with normal, abnormal, and exceptional mental abilities, and begin to trace the chain of causation in fetal development by which genes shape the brain systems that let us learn, feel, and act.

People sometimes fear that if the genes affect the mind at all they must determine it in every detail. That is wrong, for two reasons. The first is that most effects of genes are probabilistic. If one identical twin has a trait, there is usually no more than an even chance that the other will have it, despite their having a complete genome in common. Behavioral geneticists estimate that only about half of the variation in most psychological traits within a given environment correlates with the genes. In the chapter on children, we will explore what this means and where the other half of the variation comes from.

The second reason that genes aren't everything is that their effects can  {49}  vary depending on the environment. A simple example may be found in any genetic textbook. While different strains of corn grown in a single field will vary in height because of their genes, a single strain of corn grown in different fields — one arid, the other irrigated — will vary in height because of the environment. A human example comes from Woody Allen. Though his fame, fortune, and ability to attract beautiful women may depend on having genes that a sense of humor, in Stardust Memories he explains to an envious childhood friend that there is a crucial environmental factor as well: “We live la society that puts a big value on jokes.... If I had been an Apache Indian, those guys didn't need comedians, so I'd be out of work.” The meaning of findings in behavioral genetics for our understanding of human nature has to be worked out for each case. An aberrant gene that causes a disorder shows that the standard version of the gene is necessary to have a normal human mind. But what the standard version does is not immediately obvious. If a gear with a broken tooth goes clunk on every turn, we do not conclude that the tooth in its intact form was a clunk-suppressor. And so a gene that disrupts a mental ability need not be a defective version of a gene that is “for” that ability. It may produce a toxin that interferes with normal brain development, or it may leave a chink in the immune system that allows a pathogen to infect the brain, or it may make the person look stupid or sinister and thereby affect how other people react to him. In the past, geneticists couldn't rule out the boring possibilities (the ones that don't involve brain function directly), and skeptics intimated that all genetic effects might be boring, merely warping or defacing a blank slate rather than being an ineffective version of a gene that helps to give structure to a complex brain. But increasingly researchers are able to tie genes to the brain.

A promising example is the F0XP2 gene, associated with a speech and language disorder in a large family.⁵⁰ The aberrant nucleotide has been found in every impaired member of the family (and in one unrelated person with the same syndrome), but it was not found in any of the unimpaired members, nor was it found in 364 chromosomes from unrelated normal people. The gene belongs to a family of genes for transcription factors — proteins that turn on other genes — that are known to play important roles in embryogenesis. The mutation disrupts the part of the protein that latches onto a particular region of DNA, the key step in turning on the right gene at the right time. The gene appears to be strongly active in fetal brain tissue, and a closely related version found in mice is active in the developing cerebral cortex. These are signs, according to the authors of the study, that the normal version of the gene triggers a cascade of events that help organize a part of the developing brain.

The meaning of genetic variation among normal individuals (as opposed to genetic defects that cause a disorder) also has to be thought through with care. An innate difference among people is not the same thing as an innate  {50}  human nature that is universal across the species. Documenting the ways that people vary will not directly reveal the workings of human nature, any more than documenting the ways that automobiles vary will directly reveal how car engines work. Nonetheless, genetic variation certainly has implications for human nature. If there are many ways for a mind to vary genetically, the mind must have many genetically influenced parts and attributes that make the variation possible. Also, any modern conception of human nature that is rooted in biology (as opposed to traditional conceptions of human nature that are rooted in philosophy, religion, or common sense) must predict that the faculties making up human nature show quantitative variation, even if their fundamental design (how they work) is universal. Natural selection depends on genetic variation, and though it reduces that variation as it shapes organisms over the generations, it never uses it up completely.⁵¹

Whatever their exact interpretation turns out to be, the findings of behavioral genetics are highly damaging to the Blank Slate and its companion doctrines. The slate cannot be blank if different genes can make it more or less smart, articulate, adventurous, shy, happy, conscientious, neurotic, open, introverted, giggly, spatially challenged, or likely to dip buttered toast in coffee. For genes to affect the mind in all these ways, the mind must have many parts and features for the genes to affect. Similarly, if the mutation or deletion of a gene can target a cognitive ability as specific as spatial construction or a personality trait as specific as sensation-seeking, that trait may be a distinct component of a complex psyche.

Moreover, many of the traits affected by genes are far from noble. Psychologists have discovered that our personalities differ in five major ways: we are to varying degrees introverted or extroverted, neurotic or stable, incurious or open to experience, agreeable or antagonistic, and conscientious or undirected. Most of the 18,000 adjectives for personality traits in an unabridged dictionary can be tied to one of these five dimensions, including such sins and flaws as being aimless, careless, conforming, impatient, narrow, rude, self-pitying, selfish, suspicious, uncooperative, and undependable. All five of the major personality dimensions are heritable, with perhaps 40 to 50 percent of the variation in a typical population tied to differences in their genes. The unfortunate wretch who is introverted, neurotic, narrow, selfish, and undependable is probably that way in part because of his genes, and so, most likely, are the rest of us who have tendencies in any of those directions as compared with our fellows.

It's not just unpleasant temperaments that are partly heritable, but actual behavior with real consequences. Study after study has shown that a willingness to commit antisocial acts, including lying, stealing, starting fights, and destroying property, is partly heritable (though like all heritable traits it is exercised more in some environments than in others).⁵² People who commit  {51}  truly heinous acts, such as bilking elderly people out of their life savings, raping a succession of women, or shooting convenience store clerks lying on the floor during a robbery, are often diagnosed with “psychopathy” or “antisocial personality disorder.”⁵³ Most psychopaths showed signs of malice from the time they were children. They bullied smaller children, tortured animals, lied habitually, and were incapable of empathy or remorse, often despite normal family backgrounds and the best efforts of their distraught parents. Most experts on psychopathy believe that it comes from a genetic predisposition, though in some cases it may come from early brain damage.⁵⁴ In either case genetics and neuroscience are showing that a heart of darkness cannot always be blamed on parents or society.

And the genes, even if they by no means seal our fate, don't sit easily with the intuition that we are ghosts in machines either. Imagine that you are agonizing over a choice — which career to pursue, whether to get married, how to vote, what to wear that day. You have finally staggered to a decision when the phone rings. It is the identical twin you never knew you had. During the joyous conversation it comes out that she has just chosen a similar career, has decided to get married at around the same time, plans to cast her vote for the same presidential candidate, and is wearing a shirt of the same color — just as the behavioral geneticists who tracked you down would have bet. How much discretion did the “you” making the choices actually have if the outcome could have been predicted in advance, at least probabilistically, based on events that took place in your mother's Fallopian tubes decades ago?

~

The fourth bridge from biology to culture is evolutionary psychology, the study of the phylogenetic history and adaptive functions of the mind.⁵⁵ It holds out the hope of understanding the design or purpose of the mind — not in some mystical or teleological sense, but in the sense of the simulacrum of engineering that pervades the natural world. We see these signs of engineering everywhere: in eyes that seem designed to form images, in hearts that seem designed to pump blood, in wings that seem designed to lift birds in flight.

Darwin showed, of course, that the illusion of design in the natural world can be explained by natural selection. Certainly an eye is too well engineered to have arisen by chance. No wart or tumor or product of a big mutation could be lucky enough to have a lens, an iris, a retina, tear ducts, and so on, all perfectly arranged to form an image. Nor is the eye a masterpiece of engineering literally fashioned by a cosmic designer who created humans in his own image. The human eye is uncannily similar to the eyes of other organisms and has quirky vestiges of extinct ancestors, such as a retina that appears to have been installed backwards.⁵⁶ Today's organs are replicas of organs in our ancestors whose design worked better than the alternatives, thereby enabling them to become our ancestors.⁵⁷ Natural selection is the only physical process we know of  {52}  that can simulate engineering, because it is the only process in which how well something works can play a causal role in how it came to be.

Evolution is central to the understanding of life, including human life. Like all living things, we are outcomes of natural selection; we got here because we inherited traits that allowed our ancestors to survive, find mates, and reproduce. This momentous fact explains our deepest strivings: why having a thankless child is sharper than a serpent's tooth, why it is a truth universally acknowledged that a single man in possession of a good fortune must be in want of a wife, why we do not go gentle into that good night but rage, rage against the dying of the light.

Evolution is central to understanding ourselves because signs of design in human beings do not stop at the heart or the eye. For all its exquisite engineering, an eye is useless without a brain. Its output is not the meaningless patterns of a screen saver, but raw material for circuitry that computes a representation of the external world. That representation feeds other circuits that make sense of the world by imputing causes to events and placing them in categories that allow useful predictions. And that sense-making, in turn, works in the service of motives such as hunger, fear, love, curiosity, and the pursuit of status and esteem. As I mentioned, abilities that seem effortless to us — categorizing events, deducing cause and effect, and pursuing conflicting goals — are major challenges in designing an intelligent system, ones that robot designers strive, still unsuccessfully, to duplicate.

So signs of engineering in the human mind go all the way up, and that is why psychology has always been evolutionary. Cognitive and emotional faculties have always been recognized as nonrandom, complex, and useful, and that means they must be products either of divine design or of natural selection. But until recently evolution was seldom explicitly invoked within psychology, because with many topics, folk intuitions about what is adaptive are good enough to make headway. You don't need an evolutionary biologist to tell you that depth perception keeps an animal from falling off cliffs and bumping into trees, that thirst keeps it from drying out, or that it's better to remember what works and what doesn't than to be an amnesiac.

But with other aspects of our mental life, particularly in the social realm, the function of a faculty is not so easy to guess. Natural selection favors organisms that are good at reproducing in some environment. When the environment consists of rocks, grass, and snakes, it's fairly obvious which strategies work and which ones don't. But when the relevant environment consists of other members of the species evolving their own strategies, it is not so obvious. In the game of evolution, is it better to be monogamous or polygamous? Gentle or aggressive? Cooperative or selfish? Indulgent with children or stern with them? Optimistic, pragmatic, or pessimistic?

For questions like these, hunches are unhelpful, and that is why  {53}  evolutionary biology has increasingly been brought into psychology. Evolutionary biologists tell us that it is a mistake to think of anything conducive to people's well-being — group cohesion, the avoidance of violence, monogamous pair bonding, aesthetic pleasure, self-esteem — as an “adaptation.” What is “adaptive” in everyday life is not necessarily an “adaptation” in the technical sense of being a trait that was favored by natural selection in a species’ evolutionary history. Natural selection is the morally indifferent process in which the most effective replicators outreproduce the alternatives and come to prevail in a population. The selected genes will therefore be the “selfish” ones, in Richard Dawkins's metaphor — more accurately, the megalomaniacal ones, those that make the most copies of themselves.⁵⁸ An adaptation is anything brought about by the genes that helps them fulfill this metaphorical obsession, whether or not it also fulfills human aspirations. And this is a strikingly different conception from our everyday intuitions about what our faculties were designed for.

The megalomania of the genes does not mean that benevolence and co-operation cannot evolve, any more than the law of gravity proves that flight cannot evolve. It means only that benevolence, like flight, is a special state of affairs in need of an explanation, not something that just happens. It can evolve only in particular circumstances and has to be supported by a suite of cognitive and emotional faculties. Thus benevolence (and other social motives) must be dragged into the spotlight rather than treated as part of the furniture. In the sociobiological revolution of the 1970s, evolutionary biologists replaced the fuzzy feeling that organisms evolve to serve the greater good with deductions of what kinds of motives are likely to evolve when organisms interact with offspring, mates, siblings, friends, strangers, and adversaries.

When the predictions were combined with some basic facts about the hunter-gatherer lifestyle in which humans evolved, parts of the psyche that were previously inscrutable turned out to have a rationale as legible as those for depth perception and the regulation of thirst. An eye for beauty, for example, locks onto faces that show signs of health and fertility — just as one would j predict if it had evolved to help the beholder find the fittest mate.⁵⁹ The emotions of sympathy, gratitude, guilt, and anger allow people to benefit from cooperation without being exploited by liars and cheats.⁶⁰ A reputation for toughness and a thirst for revenge were the best defense against aggression in a world in which one could not call 911 to summon the police.⁶¹ Children acquire spoken language instinctively but written language only by the sweat of their brow, because spoken language has been a feature of human life for tens or hundreds of millennia whereas written language is a recent and slow-spreading invention.⁶²

None of this means that people literally strive to replicate their genes. If that's how the mind worked, men would line up outside sperm banks and  {54}  women would pay to have their eggs harvested and given away to infertile couples. It means only that inherited systems for learning, thinking, and feeling have a design that would have led, on average, to enhanced survival and reproduction in the environment in which our ancestors evolved. People enjoy eating, and in a world without junk food, that led them to nourish themselves, even if the nutritional content of the food never entered their minds. People love sex and love children, and in a world without contraception, that was enough for the genes to take care of themselves.

The difference between the mechanisms that impel organisms to behave in real time and the mechanisms that shaped the design of the organism over evolutionary time is important enough to merit some jargon. A proximate cause of behavior is the mechanism that pushes behavior buttons in real time, such as the hunger and lust that impel people to eat and have sex. An ultimate cause is the adaptive rationale that led the proximate cause to evolve, such as the need for nutrition and reproduction that gave us the drives of hunger and lust. The distinction between proximate and ultimate causation is indispensable in understanding ourselves because it determines the answer to every question of the form “Why did that person act as he did?” To take a simple example, ultimately people crave sex in order to reproduce (because the ultimate cause of sex is reproduction), but proximately they may do everything they can not to reproduce (because the proximate cause of sex is pleasure).

The difference between proximate and ultimate goals is another kind of proof that we are not blank slates. Whenever people strive for obvious rewards like health and happiness, which make sense both proximately and ultimately, one could plausibly suppose that the mind is equipped only with a desire to be happy and healthy and a cause-and-effect calculus that helps them get what they want. But people often have desires that subvert their proximate well-being, desires that they cannot articulate and that they (and their society) may try unsuccessfully to extirpate. They may covet their neighbor's spouse, eat themselves into an early grave, explode over minor slights, fail to love their stepchildren, rev up their bodies in response to a stressor that they cannot fight or flee, exhaust themselves keeping up with the Joneses or climbing the corporate ladder, and prefer a sexy and dangerous partner to a plain but dependable one. These personally puzzling drives have a transparent evolutionary rationale, and they suggest that the mind is packed with cravings shaped by natural selection, not with a generic desire for personal well-being.

Evolutionary psychology also explains why the slate is not blank. The mind was forged in Darwinian competition, and an inert medium would have been outperformed by rivals outfitted with high technology — with acute perceptual systems, savvy problem-solvers, cunning strategists, and sensitive feedback circuits. Worse still, if our minds were truly malleable they would be easily manipulated by our rivals, who could mold or condition us  {55}  into serving their needs rather than our own. A malleable mind would quickly be selected out.

Researchers in the human sciences have begun to flesh out the hypothesis that the mind evolved with a universal complex design. Some anthropologists have returned to an ethnographic record that used to trumpet differences among cultures and have found an astonishingly detailed set of aptitudes and tastes that all cultures have in common. This shared way of thinking, feeling, and living makes us look like a single tribe, which the anthropologist Donald Brown has called the Universal People, after Chomsky's Universal Grammar.⁶³ Hundreds of traits, from fear of snakes to logical operators, from romantic love to humorous insults, from poetry to food taboos, from exchange of goods to mourning the dead, can be found in every society ever documented. It's not that every universal behavior directly reflects a universal component of human nature — many arise from an interplay between universal properties of the mind, universal properties of the body, and universal properties of the world. Nonetheless, the sheer richness and detail in the rendering of the Universal People comes as a shock to any intuition that the mind is a blank slate or that cultures can vary without limit, and there is something on the list to refute almost any theory growing out of those intuitions. Nothing can substitute for seeing Brown's list in full; it is reproduced, with his permission, as an appendix (see p. 435).

The idea that natural selection has endowed humans with a universal complex mind has received support from other quarters. Child psychologists no longer believe that the world of an infant is a blooming, buzzing confusion, because they have found signs of the basic categories of mind (such as those for objects, people, and tools) in young babies.⁶⁴ Archaeologists and paleontologists have found that prehistoric humans were not brutish troglodytes but exercised their minds with art, ritual, trade, violence, cooperation, technology, and symbols.⁶⁵ And primatologists have shown that our hairy relatives are not like lab rats waiting to be conditioned but are outfitted with many complex faculties that used to be considered uniquely human, including concepts, a spatial sense, tool use, jealousy, parental love, reciprocity, peacemaking, and differences between the sexes.⁶⁶ With so many mental abilities appearing in all human cultures, in children before they have acquired culture, and in creatures that have little or no culture, the mind no longer looks like a formless lump pounded into shape by culture.

But it is the doctrine of the Noble Savage that has been most mercilessly debunked by the new evolutionary thinking. A thoroughly noble anything is an unlikely product of natural selection, because in the competition among genes for representation in the next generation, noble guys tend to finish last. Conflicts of interest are ubiquitous among living things, since two animals cannot both eat the same fish or monopolize the same mate. To the extent that  {56}  social motives are adaptations that maximize copies of the genes that produced them, they should be designed to prevail in such conflicts, and one way to prevail is to neutralize the competition. As William James put it, just a bit too flamboyantly, “We, the lineal representatives of the successful enactors of one scene of slaughter after another, must, whatever more pacific virtues we may also possess, still carry about with us, ready at any moment to burst into flame, the smoldering and sinister traits of character by means of which they lived through so many massacres, harming others, but themselves unharmed.”⁶⁷

From Rousseau to the Thanksgiving editorialist of Chapter 1, many intellectuals have embraced the image of peaceable, egalitarian, and ecology-loving natives. But in the past two decades anthropologists have gathered data on life and death in pre-state societies rather than accepting the warm and fuzzy stereotypes. What did they find? In a nutshell: Hobbes was right, Rousseau was wrong.

To begin with, the stories of tribes out there somewhere who have never heard of violence turn out to be urban legends. Margaret Mead's descriptions of peace-loving New Guineans and sexually nonchalant Samoans were based on perfunctory research and turned out to be almost perversely wrong. As the anthropologist Derek Freeman later documented, Samoans may beat or kill their daughters if they are not virgins on their wedding night, a young man who cannot woo a virgin may rape one to extort her into eloping, and the family of a cuckolded husband may attack and kill the adulterer.⁶⁸ The !Kung San of the Kalahari Desert had been described by Elizabeth Marshall Thomas as “the harmless people” in a book with that title. But as soon as anthropologists camped out long enough to accumulate data, they discovered that the !Kung San have a murder rate higher than that of American inner cities. They learned as well that a group of the San had recently avenged a murder by sneaking into the killer's group and executing every man, woman, and child as they slept.⁶⁹ But at least the !Kung San exist. In the early 1970s the New York Times Magazine reported the discovery of the “gentle Tasaday” of the Philippine rainforest, a people with no words for conflict, violence, or weapons. The Tasaday turned out to be local farmers dressed in leaves for a photo opportunity so that cronies of Ferdinand Marcos could set aside their “homeland” as a preserve and enjoy exclusive mineral and logging rights.⁷⁰

Anthropologists and historians have also been counting bodies. Many intellectuals tout the small numbers of battlefield casualties in pre-state societies as evidence that primitive warfare is largely ritualistic. They do not notice that two deaths in a band of fifty people is the equivalent of ten million deaths in a country the size of the United States. The archaeologist Lawrence Keeley has summarized the proportion of male deaths caused by war in a number of societies for which data are available:⁷¹  {57} 

The first eight bars, which range from almost 10 percent to almost 60 percent, come from indigenous peoples in South America and New Guinea. The nearly invisible bar at the bottom represents the United States and Europe in the twentieth century and includes the statistics from two world wars. Moreover, Keeley and others have noted that native peoples are dead serious when they carry out warfare. Many of them make weapons as damaging as their technology permits, exterminate their enemies when they can get away with it, and enhance the experience by torturing captives, cutting off trophies, and feasting on enemy flesh.⁷²

Counting societies instead of bodies leads to equally grim figures. In 1978 the anthropologist Carol Ember calculated that 90 percent of hunter-gatherer societies are known to engage in warfare, and 64 percent wage war at least once every two years.⁷³ Even the 90 percent figure may be an underestimate, because anthropologists often cannot study a tribe long enough to measure outbreaks that occur every decade or so (imagine an anthropologist studying the peaceful Europeans between 1918 and 1938). In 1972 another anthropologist, W. T. Divale, investigated 99 groups of hunter-gatherers from 37 cultures, and found that 68 were at war at the time, 20 had been at war five to twenty-five years before, and all the others reported warfare in the more distant past.⁷⁴ Based on these and other ethnographic surveys, Donald Brown includes conflict, rape, revenge, jealousy, dominance, and male coalitional violence as human universals.⁷⁵

It is, of course, understandable that people are squeamish about acknowledging the violence of pre-state societies. For centuries the stereotype of the  {58}  savage savage was used as a pretext to wipe out indigenous peoples and steal their lands. But surely it is unnecessary to paint a false picture of a people as peaceable and ecologically conscientious in order to condemn the great crimes against them, as if genocide were wrong only when the victims are nice guys.

The prevalence of violence in the kinds of environments in which we evolved does not mean that our species has a death wish, an innate thirst for blood, or a territorial imperative. There are good evolutionary reasons for the members of an intelligent species to try to live in peace. Many computer simulations and mathematical models have shown that cooperation pays off in evolutionary terms as long as the cooperators have brains with the right combination of cognitive and emotional faculties.⁷⁶ Thus while conflict is a human universal, so is conflict resolution. Together with all their nasty and brutish motives, all peoples display a host of kinder, gentler ones: a sense of morality, justice, and community, an ability to anticipate consequences when choosing how to act, and a love of children, spouses, and friends.⁷⁷ Whether a group of people will engage in violence or work for peace depends on which set of motives is engaged, a topic I will pursue at length in later chapters.

Not everyone will be comforted by such reassurances, though, because they eat away at the third cherished assumption of modern intellectual life. Love, will, and conscience are in the traditional job description for the soul and have always been placed in opposition to mere “biological” functions. If those faculties are “biological” too — that is, evolutionary adaptations implemented in the circuitry of the brain — then the ghost is left with even less to do and might as well be pensioned off for good.

Chapter 4

Culture Vultures

Like all men of Babylon, I have been proconsul; like all, I have been a slave. Look here — my right hand has no index finger. Look here — through this gash in my cape you can see on my stomach a crimson tattoo — it is the second letter, Beth. On nights when the moon is full, this symbol gives me power over men with the mark of Gimel, but it subjects me to those with the Aleph, who on nights when there is no moon owe obedience to those marked with the Gimel. In the half-light of dawn, in a cellar, standing before a black altar, I have slit the throats of sacred bulls. Once, for an entire lunar year, I was declared invisible — I would cry out and no one would heed my call, I would steal bread and not be beheaded....

I owe that almost monstrous variety to an institution — the Lottery — which is unknown in other nations, or at work in them imperfectly or secretly.¹

Jorge Luis Borges's story “The Lottery in Babylon” is perhaps the best depiction of the idea that culture is a set of roles and symbols that mysteriously descend on passive individuals. His lottery began as the familiar game in which a winning ticket was rewarded by a jackpot. But to enhance the suspense the operators added a few numbers that presented the ticket holder with a fine rather than a reward. They then imposed prison sentences on those who did not pay the fines, and the system expanded into a variety of nonmonetary punishments and rewards. The lottery became free, compulsory, omnipotent, and increasingly mysterious. People began to speculate on how it worked and whether it even continued to exist.

At first glance human cultures do appear to have the monstrous variety of a Borgesian lottery. Members of Homo sapiens ingest everything from maggots and worms to cow urine and human flesh. They bind, cut, scar, and stretch body parts in ways that would make the most perforated Western  {60}  teenager wince. They sanction kinky sexual practices like teenagers receiving daily fellatio from younger boys and parents arranging marriages between their five-year-olds. The apparent caprice of cultural variation leads naturally to the doctrine that culture lives in a separate universe from brains, genes, and evolution. And this separation depends in turn on the concept of a slate that is left blank by biology and written upon by culture. Now that I have tried to convince you that the slate is not blank, it is time to put culture back into the picture. That will complete the consilience that runs from the life sciences through the sciences of human nature to the social sciences, humanities, and arts.

In this chapter I will lay out an alternative to the belief that culture is like a lottery. Culture can be seen instead as a part of the human phenotype: the distinctive design that allows us to survive, prosper, and perpetuate our lineages. Humans are a knowledge-using, cooperative species, and culture emerges naturally from that lifestyle. To preview: The phenomena we call “culture” arise as people pool and accumulate their discoveries, and as they institute conventions to coordinate their labors and adjudicate their conflicts. When groups of people separated by time and geography accumulate different discoveries and conventions, we use the plural and call them cultures. Different cultures, then, don't come from different kinds of genes — Boas and his heirs were right about that — but they don't live in a separate world or stamp a shape onto formless minds either.

The first step in connecting culture to the sciences of human nature is to recognize that culture, for all its importance, is not some miasma that seeps into people through their skin. Culture relies on neural circuitry that accomplishes the feat we call learning. Those circuits do not make us indiscriminate mimics but have to work in surprisingly subtle ways to make the transmission of culture possible. That is why a focus on innate faculties of mind is not an alternative to a focus on learning, culture, and socialization, but rather an attempt to explain how they work.

Take the case of a person's mother tongue, which is a learned cultural skill par excellence. A parrot and a child both learn something when exposed to speech, but only the child has a mental algorithm that extracts words and rules from the sound wave and uses them to utter and understand an unlimited number of new sentences. The innate endowment for language is in fact an innate mechanism for learning language.² In the same way, for children to learn about culture they cannot be mere video cameras that passively record sights and sounds. They must be equipped with mental machinery that can extract the beliefs and values underlying other people's behavior so that the children themselves can become competent members of the culture.³

Even the humblest act of cultural learning — imitating the behavior of a  {61}  parent or a peer — is more complicated than it looks. To appreciate what goes on in our minds when we effortlessly learn from other people, we have to imagine what it would be like to have some other kind of mind. Fortunately, cognitive scientists have imagined it for us by plumbing the minds of robots, animals, and people whose minds are impaired.

The artificial intelligence researcher Rodney Brooks, who wants to build a robot capable of learning by imitation, immediately faced this problem when he considered using techniques for learning that are common in computer science:

The robot is observing a person opening a glass jar. The person approaches the robot and places the jar on a table near the robot. The person rubs his hands together and then sets himself to removing the lid from the jar. He grasps the glass jar in one hand and the lid in the other and begins to unscrew the lid by turning it counter-clockwise. While he is opening the jar, he pauses to wipe his brow, and glances at the robot to see what it is doing. He then resumes opening the jar. The robot then attempts to imitate the action. [But] which parts of the action to be imitated are important (such as turning the lid counter-clockwise), and which aren't (such as wiping your brow)?... How can the robot abstract the knowledge gained from this experience and apply it to a similar situation?⁴

The answer is that the robot has to be equipped with an ability to see into the mind of the person being imitated, so that it can infer the person's goals and pick out the aspects of behavior that the person intended to achieve the goal. Cognitive scientists call this ability intuitive psychology, folk psychology, or a theory of mind. (The “theory” here refers to the tacit beliefs held by a person, animal, or robot, not to the explicit beliefs of scientists.) No existing robot comes close to having this ability.

Another mind that finds it difficult to infer others’ goals is the chimpanzee's. The psychologist Laura Petitto was the principal sign language trainer for the animal known as Nim Chimpsky and lived with him for a year in a university mansion. At first glance Nim seemed to “imitate” her washing the dishes, but with an important difference. A dish was not necessarily any cleaner after Nim rubbed it with a sponge than before, and if he was given a spotless dish, Nim would “wash” it just as if it were dirty. Nim didn't get the concept of “washing,” namely using liquid to make something clean. He just mimicked her rubbing motion while enjoying the sensation of warm water over his fingers. Many laboratory experiments have shown something similar. Though chimpanzees and other primates have a reputation as imitators (“Monkey see, monkey do”), their ability to imitate in the way people do —  {62}  replicating another person's intent rather than going through the motions — is rudimentary, because their intuitive psychology is rudimentary.⁵

A mind unequipped to discern other people's beliefs and intentions, even if it can learn in other ways, is incapable of the kind of learning that perpetuates culture. People with autism suffer from an impairment of this kind. They can grasp physical representations like maps and diagrams but cannot grasp mental representations — that is, they cannot read other people's minds.⁶ Though they certainly imitate, they do it in bizarre ways. Some are prone to echolalia, repeating other people's utterances verbatim rather than extracting the grammatical patterns that would allow them to compose their own sentences. Autistics who do learn to speak on their own often use the word you as if it were their own name, because other people refer to them as you and it never occurs to them that the word is defined relative to who is addressing it to whom. If a parent knocks over a glass and says, “Oh, damn!” an autistic child might use oh damn as the word for a glass — disproving the empiricist theory that normal children can learn words merely by associating sounds and events that overlap in time. None of this is a consequence of low intelligence. Autistic children can be competent (or even savants) when solving other problems, and retarded children without autism don't show the same foibles with language and imitation. Autism is an innate neurological condition with strong genetic roots.⁷ Together with robots and chimpanzees, people with autism remind us that cultural learning is possible only because neurologically normal people have innate equipment to accomplish it.

Scientists often interpret the long childhood of members of Homo sapiens as an adaptation that allows children to acquire the vast store of information from their culture before striking out on their own as adults. If cultural learning depends on special psychological equipment, we should see the equipment up and running early in childhood. And indeed we do.

Experiments show that one-and-a-half-year-old babies are not associationists who connect overlapping events indiscriminately. They are intuitive psychologists who psych out other people's intentions before copying what they do. When an adult first exposes a baby to a word, as in “That's a toma” the baby will remember it as the name of the toy the adult was looking at at the time, not as the name of the toy the baby herself was looking at.⁸ If an adult fiddles with a gadget but indicates that the action was an accident (by saying “Whoops!”), a baby will not even bother trying to imitate him. But if the adult does the same thing but indicates that he intended the action, the baby will imitate him.⁹ And when an adult tries and fails to accomplish something (like trying to press the button on a buzzer, or trying to string a loop around a peg), the baby will imitate what the adult tried to do, not what he did do.¹⁰ As someone who studies language acquisition in children, I have continually been amazed at how early they “get” the logic of language, availing themselves of  {63}  most of the spoken vernacular by the age of three.¹¹ That, too, may be an attempt by the genome to get our culture-acquiring apparatus online as early in life as the growing brain can handle it.

Our minds, then, are fitted with mechanisms designed to read the goals of other people so we can copy their intended acts. But why would we want to? Though we take it for granted that acquiring culture is a good thing, the act of acquiring it is often spoken of with scorn. The longshoreman and philosopher Eric Hoffer wrote, “When people are free to do as they please, they usually imitate each other.” And we have a menagerie of metaphors that equate this quintessentially human ability with the behavior of animals: along with monkey see, monkey do, we have aping, parroting, sheep, lemmings, copycats, and a herd mentality.

Social psychologists have amply documented that people have a powerful urge to do as their neighbors do. When unwitting subjects are surrounded by confederates of the experimenter who have been paid to do something odd, many or most will go along. They will defy their own eyes and call a long line “short” or vice versa, nonchalantly fill out a questionnaire as smoke pours out of a heating vent, or (in a Candid Camera sketch) suddenly strip down to their underwear for no apparent reason.¹² But the social psychologists point out that human conformity, no matter how hilarious it looks in contrived experiments, has a genuine rationale in social life — indeed, two rationales.¹³

The first is informational, the desire to benefit from other people's knowledge and judgment. Weary veterans of committees say that the IQ of a group is the lowest IQ of any member of the group divided by the number of people in the group, but that is too pessimistic. In a species equipped with language, an intuitive psychology, and a willingness to cooperate, a group can pool the hard-won discoveries of members present and past and end up far smarter than a race of hermits. Hunter-gatherers accumulate the know-how to make tools, control fire, outsmart prey, and detoxify plants, and can live by this collective ingenuity even if no member could re-create it all from scratch. Also, by coordinating their behavior (say, in driving game or taking turns watching children while others forage), they can act like a big multi-headed, multi-limbed beast and accomplish feats that a die-hard individualist could not. And an array of interconnected eyes, ears, and heads is more robust than a single set with all its shortcomings and idiosyncrasies. There is a Yiddish expression offered as a reality check to malcontents and conspiracy theorists: The whole world isn't crazy.

Much of what we call culture is simply accumulated local wisdom: ways of fashioning artifacts, selecting food, dividing up windfalls, and so on. Some anthropologists, like Marvin Harris, argue that even practices that seem as arbitrary as a lottery may in fact be solutions to ecological problems.¹⁴ Cows really  {64}  should be sacred in India, he points out; they supply food (milk and butter), fuel (dung), and power (by pulling plows), so the customs protecting them thwart the temptation to kill the goose that laid the golden egg. Other cultural differences may have a rationale in reproduction.¹⁵ In some societies, men live with their paternal families and support their wives and children; in others, they live with their maternal families and support their sisters and nieces and nephews. The second arrangement tends to be found in societies where men have to spend long periods of time away from home and adultery is relatively common, so they cannot be sure that their wives’ children are theirs. Since the children of a man's mother's daughter have to be his biological kin regardless of who has been sleeping with whom, a matrilocal family allows men to invest in children who are guaranteed to carry some of their genes.

Of course, only Procrustes could argue that all cultural practices have a direct economic or genetic payoff. The second motive for conformity is normative, the desire to follow the norms of a community, whatever they are. But this, too, is not as stupidly lemminglike as it first appears. Many cultural practices are arbitrary in their specific form but not in their reason for being. There is no good reason for people to drive on the right side of the road as opposed to the left side, or vice versa, but there is every reason for people to drive on the same side. So an arbitrary choice of which side to drive on, and a widespread conformity with that choice, make a great deal of sense. Other examples of arbitrary but coordinated choices, which economists called “cooperative equilibria,” include money, designated days of rest, and the pairings of sound and meaning that make up the words in a language.

Shared arbitrary practices also help people cope with the fact that while many things in life are arranged along a continuum, decisions must often be binary.¹⁶ Children do not become adults instantaneously, nor do dating couples become monogamous partners. Rites of passage and their modern equivalent, pieces of paper like ID cards and marriage licenses, allow third parties to decide how to treat ambiguous cases — as a child or as an adult, as committed or as available — without endless haggling over differences of opinion.

And the fuzziest categories of all are other people's intentions. Is he a loyal member of the coalition (one that I would want to have in my foxhole) or a quisling who will bail out when times get tough? Does his heart lie with his father's clan or with his father-in-law's? Is she a suspiciously merry widow or just getting on with her life? Is he dissing me or just in a hurry? Initiation rites, tribal badges, prescribed periods of mourning, and ritualized forms of address may not answer these questions definitively, but they can remove clouds of suspicion that would otherwise hang over people's heads.

When conventions are widely enough entrenched, they can become a kind of reality even though they exist only in people's minds. In his book The Construction of Social Reality (not to be confused with the social construction of  {65}  reality), the philosopher John Searie points out that certain facts are objectively true just because people act as if they are true.¹⁷ For example, it is a matter of fact, not opinion, that George W. Bush is the forty-third president of the United States, that O. J. Simpson was found not guilty of murder, that the Boston Celtics won the NBA World Championship in 1986, and that a Big Mac at the time of this writing) costs $2.62. But though these are objective facts, :hey are not facts about the physical world, like the atomic number of cadmium or the classification of a whale as a mammal. They consist in a shared understanding in the minds of most members in a community, usually agreements to grant (or deny) power or status to certain other people.

Life in complex societies is built on social realities, the most obvious examples being money and the rule of law. But a social fact depends entirely on the willingness of people to treat it as a fact. It is specific to a community, as we see when people refuse to honor a foreign currency or fail to recognize the sovereignty of a self-proclaimed leader. And it can dissolve with changes in the collective psychology, as when a currency becomes worthless through hyperinflation or a regime collapses because people defy the police and army en masse. (Searle points out that Mao was only half right when he said that “political power grows out of the barrel of a gun.” Since no regime can keep a gun trained on every last citizen, political power grows out of a regime's ability to command the fear of enough people at the same time.) Social reality exists only within a group of people, but it depends on a cognitive ability present in each individual: the ability to understand a public agreement to confer power or status, and to honor it as long as other people do.

How does a psychological event — an invention, an affectation, a decision to treat a certain kind of person in a certain way — turn into a sociocultural fact — a tradition, a custom, an ethos, a way of life? We should understand culture, according to the cognitive anthropologist Dan Sperber, as the epidemiology of mental representations: the spread of ideas and practices from person to person.¹⁸ Many scientists now use the mathematical tools of epidemiology (how diseases spread) or of population biology (how genes and organisms spread) to model the evolution of culture.¹⁹ They have shown how a tendency of people to adopt the innovations of other people can lead to effects that we understand using metaphors like epidemics, wildfire, snowballs, and tipping points. Individual psychology turns into collective culture.

Culture, then, is a pool of technological and social innovations that people accumulate to help them live their lives, not a collection of arbitrary roles and symbols that happen to befall them. This idea helps explain what makes cultures different and similar. When a splinter group leaves the tribe and is cut off by an ocean, a mountain range, or a demilitarized zone, an innovation on one side of the barrier has no way of diffusing to the other side. As each group  {66}  modifies its own collection of discoveries and conventions, the collections will diverge and the groups will have different cultures. Even when two groups stay within shouting distance, if their relationship has an edge of hostility they may adopt behavioral identity badges that advertise which side someone is on, further exaggerating any differences. This branching and differentiation is easily visible in the evolution of languages, perhaps the clearest example of cultural evolution. And as Darwin pointed out, it has a close parallel in the origin of species, which often arise when a population splits in two and the groups of descendants evolve in different directions.²⁰ As with languages and species, cultures that split apart more recently tend to be more similar. The traditional cultures of Italy and France, for example, are more similar to each other than either is to the cultures of the Maoris and Hawaiians.

The psychological roots of culture also help explain why some bits of culture change and others stay put. Some collective practices have enormous inertia because they impose a high cost on the first individual who would try to change them. A switch from driving on the left to driving on the right could not begin with a daring nonconformist or a grass-roots movement but would have to be imposed from the top down (which is what happened in Sweden at 5 a.m., Sunday, September 3, 1967). Other examples are laying down your weapons when hostile neighbors are armed to the teeth, abandoning the QWERTY keyboard layout, and pointing out that the emperor is not wearing any clothes.

But traditional cultures can change, too, and more dramatically than most people realize. Preserving cultural diversity is considered a supreme virtue today, but the members of the diverse cultures don't always see it that way. People have wants and needs, and when cultures rub shoulders, people in one culture are bound to notice when their neighbors are satisfying those desires better than they are. When they do notice, history tells us, they shamelessly borrow whatever works best. Far from being self-preserving monoliths, cultures are porous and constantly in flux. Language, once again, is a clear example. Notwithstanding the perennial lamentations of purists and the sanctions of language academies, no language is ever spoken the way it was centuries before. Just compare contemporary English with the language of Shakespeare, or the language of Shakespeare with the language of Chaucer. Many other “traditional” practices are surprisingly recent. The ancestors of the Hasidic Jews did not wear black coats and fur-lined hats in Levantine deserts, nor did the Plains Indians ride horses before the arrival of the Europeans. National cuisines, too, have shallow roots. Potatoes in Ireland, paprika in Hungary, tomatoes in Italy, hot chile peppers in India and China, and cassava in Africa come from New World plants, and were brought to their “traditional” homes in the centuries after the arrival of Columbus in the Americas.²¹

The idea that a culture is a tool for living can even explain the fact that first led Boas to argue the opposite, that a culture is an autonomous system of  {67}  ideas. The most obvious cultural difference on the planet is that some cultures are materially more successful than others. In past centuries, cultures from Europe and Asia decimated the cultures of Africa, the Americas, Australia, and rhe Pacific. Even within Europe and Asia the fortunes of cultures have varied widely, some developing expansive civilizations rich in art, science, and technology, others stuck in poverty and helpless to resist conquest. What allowed small groups of Spaniards to cross the Atlantic and defeat the great empires of the Incas and Aztecs, rather than the other way around? Why didn't African tribes colonize Europe instead of vice versa? The immediate answer is that the wealthy conquerors had better technology and a more complex political and economic organization. But that simply pushes back the question of why some cultures develop more complex ways of life than others.

Boas helped overthrow the bad racial science of the nineteenth century that attributed these disparities to differences in how far each race had biologically evolved. In its place his successors stipulated that behavior is determined by culture and that culture is autonomous from biology.²² Unfortunately, that left the dramatic differences among cultures unexplained, as if they were random outcomes of the lottery in Babylon. Indeed, the differences were not just unexplained but unmentionable, out of a fear that people would misinterpret the observation that some cultures were more technologically sophisticated than others as some kind of moral judgment that advanced societies were better than primitive ones. But no one can fail to notice that some cultures can accomplish things that all people want (like health and comfort) better than others. The dogma that cultures vary capriciously is a feeble refutation of any private opinion that some races have what it takes to develop science, technology, and government and others don't.

But recently two scholars, working independently, have decisively shown that there is no need to invoke race to explain differences among cultures. Both arrived at that conclusion by eschewing the Standard Social Science Model, in which cultures are arbitrary symbol systems that exist apart from the minds of individual people. In his trilogy Race and Culture, Migrations and Cultures, and Conquests and Cultures, the economist Thomas Sowell explained his starting point for an analysis of cultural differences:

A culture is not a symbolic pattern, preserved like a butterfly in amber. Its place is not in a museum but in the practical activities of daily life, where it evolves under the stress of competing goals and other competing cultures. Cultures do not exist as simply static “differences” to be celebrated but compete with one another as better and worse ways of getting things done — better and worse, not from the standpoint of some observer, but from the standpoint of the peoples themselves, as they cope and aspire amid the gritty realities of life.²³  {68} 

The physiologist Jared Diamond is a proponent of ideas in evolutionary psychology and of consilience between the sciences and the humanities, particularly history.²⁴ In Guns, Germs, and Steel he rejected the standard assumption that history is just one damn thing after another and tried to explain the sweep of human history over tens of thousands of years in the context of human evolution and ecology.²⁵ Sowell and Diamond have made an authoritative case that the fates of human societies come neither from chance nor from race but from the human drive to adopt the innovations of others, combined with the vicissitudes of geography and ecology.

Diamond begins at the beginning. For most of human evolutionary history we lived as hunter-gatherers. The trappings of civilization — sedentary living, cities, a division of labor, government, professional armies, writing, metallurgy — sprang from a recent development, farming, about ten thousand years ago. Farming depends on plants and animals that can be tamed and exploited, and only a few species are suited to it. They happened to be concentrated in a few parts of the world, including the Fertile Crescent, China, and Central and South America. The first civilizations arose in those regions.

From then on, geography was destiny. Diamond and Sowell point out that Eurasia, the world's largest landmass, is an enormous catchment area for local innovations. Traders, sojourners, and conquerors can collect them and spread them, and people living at the crossroads can concentrate them into a high-tech package. Also, Eurasia runs in an east-west direction, whereas Africa and the Americas run north-south. Crops and animals that are domesticated in one region can easily be spread to others along lines of latitude, which are also lines of similar climate. But they cannot be spread as easily along lines of longitude, where a few hundred miles can spell the difference between temperate and tropical climates. Horses domesticated in the Asian steppes, for example, could make their way westward to Europe and eastward to China, but llamas and alpacas domesticated in the Andes never made it northward to Mexico, so the Mayan and Aztec civilizations were left without pack animals. And until recently the transportation of heavy goods over long distances (and with them traders and their ideas) was possible only by water. Europe and parts of Asia are blessed by a notchy, furrowed geography with many natural harbors and navigable rivers. Africa and Australia are not.

So Eurasia conquered the world not because Eurasians are smarter but because they could best take advantage of the principle that many heads are better than one. The “culture” of any of the conquering nations of Europe, such as Britain, is in fact a greatest-hits collection of inventions assembled across thousands of miles and years. The collection is made up of cereal crops and alphabetic writing from the Middle East, gunpowder and paper from China, domesticated horses from Ukraine, and many others. But the necessarily insular cultures of Australia, Africa, and the Americas had to make do with a few  {69}  homegrown technologies, and as a result they were no match for their pluralistic conquerors. Even within Eurasia and (later) the Americas, cultures that were isolated by mountainous geography — for example, in the Appalachians, the Balkans, and the Scottish highlands — remained backward for centuries in comparison with the vast network of people around them.

The extreme case, Diamond points out, is Tasmania. The Tasmanians, who were nearly exterminated by Europeans in the nineteenth century, were the most technologically primitive people in recorded history. Unlike the Aborigines on the Australian mainland, the Tasmanians had no way of making tire, no boomerangs or spear throwers, no specialized stone tools, no axes with handles, no canoes, no sewing needles, and no ability to fish. Amazingly, the archaeological record shows that their ancestors from the Australian mainland had arrived with these technologies ten thousand years before. But then the land bridge connecting Tasmania to the mainland was submerged and the island was cut off from the rest of the world. Diamond speculates that any technology can be lost from a culture at some point in its history. Perhaps a raw material came to be in short supply and people stopped making the products that depended on it. Perhaps all the skilled artisans in a generation were killed by a freak storm. Perhaps some prehistoric Luddite or ayatollah imposed a taboo on the practice for one inane reason or another. Whenever this happens n a culture that rubs up against other ones, the lost technology can eventually be reacquired as the people clamor for the higher standard of living enjoyed by their neighbors. But in lonely Tasmania, people would have had to reinvent the proverbial wheel every time it was lost, and so their standard of living ratcheted downward.

The ultimate irony of the Standard Social Science Model is that it failed to accomplish the very goal that brought it into being: explaining the different fortunes of human societies without invoking race. The best explanation today is thoroughly cultural, but it depends on seeing a culture as a product of human desires rather than as a shaper of them.

History and culture, then, can be grounded in psychology, which can be grounded in computation, neuroscience, genetics, and evolution. But this kind of talk sets off alarms in the minds of many nonscientists. They fear that consilience is a smokescreen for a hostile takeover of the humanities, arts, and social sciences by philistines in white coats. The richness of their subject matter would be dumbed down into a generic palaver about neurons, genes, and evolutionary urges. This scenario is often called “reductionism,” and I will conclude the chapter by showing why consilience does not call for it.

Reductionism, like cholesterol, comes in good and bad forms. Bad reductionism — also called “greedy reductionism” or “destructive reductionism” — consists of trying to explain a phenomenon in terms of its smallest or simplest  {70}  constituents. Greedy reductionism is not a straw man. I know several scientists who believe (or at least say to granting agencies) that we will make break-throughs in education, conflict resolution, and other social concerns by studying the biophysics of neural membranes or the molecular structure of the synapse. But greedy reductionism is far from the majority view, and it is easy to show why it is wrong. As the philosopher Hilary Putnam has pointed out, even the simple fact that a square peg won't fit into a round hole cannot be explained in terms of molecules and atoms but only at a higher level of analysis involving rigidity (regardless of what makes the peg rigid) and geometry.²⁶ And if anyone really thought that sociology or literature or history could be replaced by biology, why stop there? Biology could in turn be ground up into chemistry, and chemistry into physics, leaving one struggling to explain the causes of World War I in terms of electrons and quarks. Even if World War I consisted of nothing but a very, very large number of quarks in a very, very complicated pattern of motion, no insight is gained by describing it that way.

Good reductionism (also called hierarchical reductionism) consists not of replacing one field of knowledge with another but of connecting or unifying them. The building blocks used by one field are put under a microscope by another. The black boxes get opened; the promissory notes get cashed. A geographer might explain why the coastline of Africa fits into the coastline of the Americas by saying that the landmasses were once adjacent but sat on different plates, which drifted apart. The question of why the plates move gets passed on to the geologists, who appeal to an upwelling of magma that pushes them apart. As for how the magma got so hot, they call in the physicists to explain the reactions in the Earth's core and mantle. None of the scientists is dispensable. An isolated geographer would have to invoke magic to move the continents, and an isolated physicist could not have predicted the shape of South America.

So, too, for the bridge between biology and culture. The big thinkers in the sciences of human nature have been adamant that mental life has to be understood at several levels of analysis, not just the lowest one. The linguist Noam Chomsky, the computational neuroscientist David Marr, and the ethologist Niko Tinbergen have independently marked out a set of levels of analysis for understanding a faculty of the mind. These levels include its function (what it accomplishes in an ultimate, evolutionary sense); its real-time operation (how it works proximately, from moment to moment); how it is implemented in neural tissue; how it develops in the individual; and how it evolved in the species.²⁷ For example, language is based on a combinatorial grammar designed to communicate an unlimited number of thoughts. It is utilized by people in real time via an interplay of memory lookup and rule application. It is implemented in a network of regions in the center of the left cerebral hemisphere that must coordinate memory, planning, word meaning, and grammar.  {71}  It develops in the first three years of life in a sequence from babbling to words to word combinations, including errors in which rules maybe overapplied. It evolved through modifications of a vocal tract and brain circuitry that had other uses in earlier primates, because the modifications allowed our ancestors to prosper in a socially interconnected, knowledge-rich lifestyle. None of these levels can be replaced by any of the others, but none can be fully understood in isolation from the others.

Chomsky distinguishes all of these from yet another level of analysis (one that he himself has little use for but that other language scholars invoke). The vantage points I just mentioned treat language as an internal, individual entity, such as the knowledge of Canadian English that I possess in my head. But Language can also be understood as an external entity: the “English language” as a whole, with its fifteen-hundred-year history, its countless dialects and hybrids spanning the globe, its half a million words in the Oxford English Dictionary. An external language is an abstraction that pools the internal languages of hundreds of millions of people living in different places and times. It could not exist without the internal languages in the minds of real humans conversing with one another, but it cannot be reduced to what any of them knows either. For example, the statement “English has a larger vocabulary than Japanese” could be true even if no English speaker has a larger vocabulary than any Japanese speaker.

The English language was shaped by broad historical events that did not take place inside a single head. They include the Scandinavian and Norman invasions in medieval times, which infected it with non-Anglo-Saxon words; the Great Vowel Shift of the fifteenth century, which scrambled the pronunciation of the long vowels and left its spelling system an irregular mess; the expansion of the British Empire, which budded off a variety of Englishes (American, Australian, Singaporean); and the development of global electronic media, which may rehomogenize the language as we all read the same web pages and watch the same television shows.

At the same time, none of these forces can be understood without taking into account the thought processes of flesh-and-blood people. They include the Britons who reanalyzed French words when they absorbed them into English, the children who failed to remember irregular past-tense forms like writhe-wrothe and crow-crew and converted them into regular verbs, the aristocrats who affected fussy pronunciations to differentiate themselves from the rabble, the mumblers who swallowed consonants to leave us made and had (originally maked and haved), and the clever speakers who first converted I had the house built to I had built the house and inadvertently gave English its perfect tense. Language is re-created every generation as it passes through the minds of the humans who speak it.²⁸

External language is, of course, a fine example of culture, the province of  {72}  social scientists and scholars in the humanities. The way that language can be understood at some half-dozen connected levels of analysis, from the brain and evolution to the cognitive processes of individuals to vast cultural systems, shows how culture and biology may be connected. The possibilities for connections in other spheres of human knowledge are plentiful, and we will encounter them throughout the book. The moral sense can illuminate legal and ethical codes. The psychology of kinship helps us understand sociopolitical arrangements. The mentality of aggression helps to make sense of war and conflict resolution. Sex differences are relevant to gender politics. Human aesthetics and emotion can enlighten our understanding of the arts.

What is the payoff for connecting the social and cultural levels of analysis to the psychological and biological ones? It is the thrill of discoveries that could never be made within the boundaries of a single discipline, such as universals of beauty, the logic of language, and the components of the moral sense. And it is the uniquely satisfying understanding we have enjoyed from the unification of the other sciences — the explanation of muscles as tiny magnetic ratchets, of flowers as lures for insects, of the rainbow as a splaying of wavelengths that ordinarily blend into white. It is the difference between stamp collecting and detective work, between slinging around jargon and offering insight, between saying that something just is and explaining why it had to be that way as opposed to some other way it could have been. In a talk-show parody in Monty Python's Flying Circus, an expert on dinosaurs trumpets her new theory of the brontosaurus: “All brontosauruses are thin at one end; much, much thicker in the middle; and then thin again at the far end.” We laugh because she has not explained her subject in terms of deeper principles — she has not “reduced” it, in the good sense. Even the word understand — literally, “stand under” — alludes to descending to a deeper level of analysis.

Our understanding of life has only been enriched by the discovery that living flesh is composed of molecular clockwork rather than quivering protoplasm, or that birds soar by exploiting the laws of physics rather than defying them. In the same way, our understanding of ourselves and our cultures can only be enriched by the discovery that our minds are composed of intricate neural circuits for thinking, feeling, and learning rather than blank slates, amorphous blobs, or inscrutable ghosts.

Chapter 5

The Slate's Last Stand

Human nature is a scientific topic, and as new facts come in, our conception of it will change. Sometimes the facts may show that a theory grants our minds too much innate structure. For example, perhaps our language faculties are equipped not with nouns, verbs, adjectives, and prepositions but only with a distinction between more nounlike and more verblike parts of speech. At other times a theory may turn out to have granted our minds too little innate structure. No current theory of personality can explain why both members of a pair of identical twins reared apart liked to keep rubber bands around their wrists and pretend to sneeze in crowded elevators.

Also up for grabs is exactly how our minds use the information coming in from the senses. Once our faculties for language and social interaction are up and running, some kinds of learning may consist of simply recording information for future use, like the name of a person or the content of a new piece of legislation. Others may be more like setting a dial, flipping a switch, or computing an average, where the apparatus is in place but a parameter is left open so the mind can track variation in the local environment. Still others may use the information provided by all normal environments, such as the presence of gravity or the statistics of colors and lines in the visual field, to tune up our sensorimotor systems. There are yet other ways that nature and nurture might interact, and many will blur the distinction between the two.

This book is based on the estimation that whatever the exact picture turns out to be, a universal complex human nature will be part of it. I think we have reason to believe that the mind is equipped with a battery of emotions, drives, and faculties for reasoning and communicating, and that they have a common logic across cultures, are difficult to erase or redesign from scratch, were shaped by natural selection acting over the course of human evolution, and owe some of their basic design (and some of their variation) to information in the genome. This general picture is meant to embrace a variety of theories, present and future, and a range of foreseeable scientific discoveries.  {74} 

But the picture does not embrace just any theory or discovery. Conceivably scientists might discover that there is insufficient information in the genome to specify any innate circuitry, or no known mechanism by which it could be wired into the brain. Or perhaps they will discover that brains are made out of general-purpose stuff that can soak up just about any pattern in the sensory input and organize itself to accomplish just about any goal. The former discovery would make innate organization impossible; the latter would make it unnecessary. Those discoveries would call into question the very concept of human nature. Unlike the moral and political objections to the concept of human nature (objections that I discuss in the rest of this book), these would be scientific objections. If such discoveries are on the horizon, I had better look at them carefully.

This chapter is about three scientific developments that are sometimes interpreted as undermining the possibility of a complex human nature. The first comes from the Human Genome Project. When the sequence of the human genome was published in 2001, geneticists were surprised that the number of genes was lower than they had predicted. The estimates hovered around 34,000 genes, which lies well outside the earlier range of 50,000 to 100,000.¹ Some editorialists concluded that the smaller gene count refuted any claim about innate talents or tendencies, because the slate is too small to contain much writing. Some even saw it as vindicating the concept of free will: the smaller the machine, the more room for a ghost.

The second challenge comes from the use of computer models of neural networks to explain cognitive processes. These artificial neural networks can often be quite good at learning statistical patterns in their input. Some modelers from the school of cognitive science called connectionism suggest that generic neural networks can account for all of human cognition, with little or no innate tailoring for particular faculties such as social reasoning or language. In Chapter 2 we met the founders of connectionism, David Rumelhart and James McClelland, who suggested that people are smarter than rats only because they have more associative cortex and because their environment contains a culture to organize it.

The third comes from the study of neural plasticity, which examines how the brain develops in the womb and early childhood and how it records experience as the animal learns. Neuroscientists have recently shown how the brain changes in response to learning, practice, and input from the senses. One spin on these discoveries may be called extreme plasticity. According to this slant, the cerebral cortex — the convoluted gray matter responsible for perception, thinking, language, and memory — is a protean substance that can be shaped almost limitlessly by the structure and demands of the environment. The blank slate becomes the plastic slate.

Connectionism and extreme plasticity are popular among cognitive  {75}  scientists at the West Pole, who reject a completely blank slate but want to restrict innate organization to simple biases in attention and memory. Extreme plasticity also appeals to neuroscientists who wish to boost the importance of their field for education and social policy, and to entrepreneurs selling products to speed up infant development, cure learning disabilities, or slow down aging. Outside the sciences, all three developments have been welcomed by some scholars in the humanities who want to beat back the encroachments of biology.² The lean genome, connectionism, and extreme plasticity are the Blank Slate's last stand.

The point of this chapter is that these claims are not vindications of the doctrine of the Blank Slate but products of the Blank Slate. Many people (including a few scientists) have selectively read the evidence, sometimes in bizarre ways, to fit with a prior belief that the mind cannot possibly have any innate structure, or with simplistic notions of how innate structure, if it did exist, would be encoded in the genes and develop in the brain.

I should say at the outset that I find these latest-and-best blank-slate theories highly implausible — indeed, barely coherent. Nothing comes out of nothing, and the complexity of the brain has to come from somewhere. It cannot come from the environment alone, because the whole point of having a brain is to accomplish certain goals, and the environment has no idea what those goals are. A given environment can accommodate organisms that build dams, migrate by the stars, trill and twitter to impress the females, scent-mark trees, write sonnets, and so on. To one species, a snatch of human speech is a warning to flee; to another, it is an interesting new sound to incorporate into its own vocal repertoire; to a third, it is grist for grammatical analysis. Information in the world doesn't tell you what to do with it.

Also, brain tissue is not some genie that can grant its owner any power that would come in handy. It is a physical mechanism, an arrangement of matter that converts inputs to outputs in particular ways. The idea that a single generic substance can see in depth, control the hands, attract a mate, bring up children, elude predators, outsmart prey, and so on, without some degree of specialization, is not credible. Saying that the brain solves these problems because of its “plasticity” is not much better than saying it solves them by magic. Still, in this chapter I will examine the latest scientific objections to human nature carefully. Each of the discoveries is important on its own terms, even if it does not support the extravagant conclusions that have been drawn. And once the last supports for the Blank Slate have been evaluated, I can properly sum up the scientific case for the alternative.

The human genome is often seen as the essence of our species, so it is not surprising that when its sequence was announced in 2001 commentators rushed to give it the correct interpretation for human affairs. Craig Venter,  {76}  whose company had competed with a public consortium in the race to sequence the genome, said at a press conference that the smaller-than-expected gene count shows that “we simply do not have enough genes for this idea of biological determinism to be right. The wonderful diversity of the human species is not hard-wired in our genetic code. Our environments are critical.” In the United Kingdom, The Guardian headlined its story, “Revealed: The Secret of Human Behaviour. Environment, Not Genes, Key to Our Acts.”³ An editorial in another British newspaper concluded that “we are more free, it seems, than we had realized.” Moreover, the finding “offers comfort for the left, with its belief in the potential of all, however deprived their background. But it is damning for the right, with its fondness for ruling classes and original sin.”⁴

All this from the number 34,000! Which leads to the question, What number of genes would have proven that the diversity of our species was wired into our genetic code, or that we are less free than we had realized, or that the political right is right and the left is wrong? 50,000? 150,000? Conversely, if it turned out that we had only 20,000 genes, would that have made us even freer, or the environment even more important, or the political left even more comfortable? The fact is that no one knows what these numbers mean. No one has the slightest idea how many genes it would take to build a system of hard-wired modules, or a general-purpose learning program, or anything in between — to say nothing of original sin or the superiority of the ruling class. In our current state of ignorance of how the genes build a brain, the number of genes in the human genome is just a number.

If you don't believe this, consider the roundworm Caenorhabditis elegans, which has about 18,000 genes. By the logic of the genome editorialists, it should be twice as free, be twice as diverse, and have twice as much potential as a human being. In fact, it is a microscopic worm composed of 959 cells grown by a rigid genetic program, with a nervous system consisting of exactly 302 neurons in a fixed wiring diagram. As far as behavior is concerned, it eats, mates, approaches and avoids certain smells, and that's about it. This alone should make it obvious that our freedom and diversity of behavior come from having a complex biological makeup, not a simple one.

Now, it is a genuine puzzle why humans, with their hundred trillion cells and hundred billion neurons, need only twice as many genes as a humble little worm. Many biologists believe that the human genes have been undercounted. The number of genes in a genome can only be estimated; right now they cannot literally be totted up. Gene-estimating programs look for sequences in the DNA that are similar to known genes and that are active enough to be caught in the act of building a protein.⁵ Genes that are unique to humans or active only in the developing brain of the fetus — the genes most relevant to human nature — and other inconspicuous genes could evade the software and get left  {77}  out of the estimates. Alternative estimates of 57,000,75,000, and even 120,000 human genes are currently being bruited about.⁶ Still, even if humans had six times as many genes as a roundworm rather than just twice as many, the puzzle would remain.

Most biologists who are pondering the puzzle don't conclude that humans are less complex than we thought. Instead they conclude that the number of genes in a genome has little to do with the complexity of the organism.⁷ A single gene does not correspond to a single component in such a way that an organism with 20,000 genes has 20,000 components, an organism with 30,000 genes has 30,000 components, and so on. Genes specify proteins, and some of the proteins do become the meat and juices of an organism. But other proteins turn genes on or off, speed up or slow down their activity, or cut and splice other proteins into new combinations. James Watson points out that we should recalibrate our intuitions about what a given number of genes can do: “Imagine watching a play with thirty thousand actors. You'd get pretty conrused.”

Depending on how the genes interact, the assembly process can be much more intricate for one organism than for another with the same number of genes. In a simple organism, many of the genes simply build a protein and dump it into the stew. In a complex organism, one gene may turn on a second one, which speeds up the activity of a third one (but only if a fourth one is active), which then turns off the original gene (but only if a fifth one is inactive), and so on. This defines a kind of recipe that can build a more complex organism out of the same number of genes. The complexity of an organism thus depends not just on its gene count but on the intricacy of the box-and-arrow diagram that captures how each gene impinges on the activity of the other genes.⁸ And because adding a gene doesn't just add an ingredient but can multiply the number of ways that the genes can interact with one another, the complexity of organisms depends on the number of possible combinations of active and inactive genes in their genomes. The geneticist Jean-Michel Claverie suggests that it might be estimated by the number two (active versus inactive) raised to the power of the number of genes. By that measure, a human genome is not twice as complex as a roundworm genome but 2^16,000 (a one followed by 4.800 zeroes) times as complex.⁹

There are two other reasons why the complexity of the genome is not reflected in the number of genes it contains. One is that a given gene can produce not just one protein but several. A gene is typically broken into stretches of DNA that code for fragments of protein (exons) separated by stretches of DNA that don't (introns), a bit like a magazine article interrupted by ads. The segments of a gene can then be spliced together in multiple ways. A gene composed of exons A, B, C, and D might give rise to proteins corresponding to  {78}  ABC, ABD, ACD, and so on — as many as ten different proteins per gene. This happens to a greater degree in complex organisms than in simple ones.¹⁰

Second, the 34,000 genes take up only about 3 percent of the human genome. The rest consists of DNA that does not code for protein and that used to be dismissed as “junk.” But as one biologist recently put it, “The term ‘junk DNA’ is a reflection of our ignorance.”¹¹ The size, placement, and content of the noncoding DNA can have dramatic effects on the way that nearby genes are activated to make proteins. Information in the billions of bases in the non-coding regions of the genome is part of the specification of a human being, above and beyond the information contained in the 34,000 genes.

The human genome, then, is fully capable of building a complex brain, in spite of the bizarre proclamations of how wonderful it is that people are almost as simple as worms. Of course “the wonderful diversity of the human species is not hard-wired in our genetic code,” but we didn't need to count genes to figure that out — we already know it from the fact that a child growing up in Japan speaks Japanese but the same child growing up in England would speak English. It is an example of a syndrome we will meet elsewhere in this book: scientific findings spin-doctored beyond recognition to make a moral point that could have been made more easily on other grounds.

The second scientific defense of the Blank Slate comes from connectionism, the theory that the brain is like the artificial neural networks simulated on computers to learn statistical patterns.¹²

Cognitive scientists agree that the elementary processes that make up the instruction set of the brain — storing and retrieving an association, sequencing elements, focusing attention — are implemented in the brain as networks of densely interconnected neurons (brain cells). The question is whether a generic kind of network, after being shaped by the environment, can explain all of human psychology, or whether the genome tailors different networks to the demands of particular domains: language, vision, morality, fear, lust, intuitive psychology, and so on. The connectionists, of course, do not believe in a blank slate, but they do believe in the closest mechanistic equivalent, a general-purpose learning device.

What is a neural network? Connectionists use the term to refer not to real neural circuitry in the brain but to a kind of computer program based on the metaphor of neurons and neural circuits. In the most common approach, a “neuron” carries information by being more or less active. The activity level indicates the presence or absence (or intensity or degree of confidence) of a simple feature of the world. The feature may be a color, a line with a certain slant, a letter of the alphabet, or a property of an animal such as having four legs.

A network of neurons can represent different concepts, depending on  {79}  which ones are active. If neurons for “yellow,” “flies,” and “sings” are active, the network is thinking about a canary; if neurons for “silver,” “flies,” and “roars” are active, it is thinking about an airplane. An artificial neural network computes in the following manner. Neurons are linked to other neurons by connections that work something like synapses. Each neuron counts up the inputs from other neurons and changes its activity level in response. The network learns by allowing the input to change the strengths of the connections. The strength of a connection determines the likelihood that the input neuron will excite or inhibit the output neuron.

Depending on what the neurons stand for, how they are innately wired, and how the connections change with training, a connectionist network can learn to compute various things. If everything is connected to everything else, a network can soak up the correlations among features in a set of objects. For example, after exposure to descriptions of many birds it can predict that feathered singing things tend to fly or that feathered flying things tend to sing or that singing flying things tend to have feathers. If a network has an input layer connected to an output layer, it can learn associations between ideas, such as that small soft flying things are animals but large metallic flying things are vehicles. If its output layer feeds back to earlier layers, it can crank out ordered sequences, such as the sounds making up a word.

The appeal of neural networks is that they automatically generalize their training to similar new items. If a network has been trained that tigers eat Frosted Flakes, it will tend to generalize that lions eat Frosted Flakes, because eating Frosted Flakes” has been associated not with “tigers” but with simpler features like “roars” and “has whiskers,” which make up part of the representation of h'ons, too. The school of connectionism, like the school of associationism championed by Locke, Hume, and Mill, asserts that these generalizations are the crux of intelligence. If so, highly trained but otherwise generic neural networks can explain intelligence.

Computer modelers often set their models on simplified toy problems to ?rove that they can work in principle. The question then becomes whether the models can “scale up” to more realistic problems, or whether, as skeptics say, the modeler “is climbing trees to get to the moon.” Here we have the problem with connectionism. Simple connectionist networks can manage impressive displays of memory and generalization in circumscribed problems like reading a list of words or learning stereotypes of animals. But they are simply too underpowered to duplicate more realistic feats of human intelligence like understanding a sentence or reasoning about living things.

Humans don't just loosely associate things that resemble each other, or things that tend to occur together. They have combinatorial minds that enterrain propositions about what is true of what, and about who did what to  {80}  whom, when and where and why. And that requires a computational architecture that is more sophisticated than the uniform tangle of neurons used in generic connectionist networks. It requires an architecture equipped with logical apparatus like rules, variables, propositions, goal states, and different kinds of data structures, organized into larger systems. Many cognitive scientists have made this point, including Gary Marcus, Marvin Minsky, Seymour Papert, Jerry Fodor, Zenon Pylyshyn, John Anderson, Tom Bever, and Robert Hadley, and it is acknowledged as well by neural network modelers who are not in the connectionist school, such as John Hummel, Lokendra Shastri, and Paul Smolensky.¹³ I have written at length on the limits of connectionism, both in scholarly papers and in popular books; here is a summary of my own case.¹⁴

In a section called “Connectoplasm” in How the Mind Works, I laid out some simple logical relationships that underlie our understanding of a complete thought (such as the meaning of a sentence) but that are difficult to represent in generic networks.¹⁵ One is the distinction between a kind and an individual: between ducks in general and this duck in particular. Both have the same features (swims, quacks, has feathers, and so on), and both are thus represented by the same set of active units in a standard connectionist model. But people know the difference.

A second talent is compositionality: the ability to entertain a new, complex thought that is not just the sum of the simple thoughts composing it but depends on their relationships. The thought that cats chase mice, for example, cannot be captured by activating a unit each for “cats,” “mice,” and “chase,” because that pattern could just as easily stand for mice chasing cats.

A third logical talent is quantification (or the binding of variables): the difference between fooling some of the people all of the time and fooling all of the people some of the time. Without the computational equivalent of x's,y's, parentheses, and statements like “For all x,” a model cannot tell the difference.

A fourth is recursion: the ability to embed one thought inside another, so that we can entertain not only the thought that Elvis lives, but the thought that the National Enquirer reported that Elvis lives, that some people believe the National Enquirer report that Elvis lives, that it is amazing that some people believe the National Enquirer report that Elvis lives, and so on. Connectionist networks would superimpose these propositions and thereby confuse their various subjects and predicates.

A final elusive talent is our ability to engage in categorical, as opposed to fuzzy, reasoning: to understand that Bob Dylan is a grandfather, even though he is not very grandfatherly, or that shrews are not rodents, though they look just like mice. With nothing but a soup of neurons to stand for an object's properties, and no provision for rules, variables, and definitions, the networks fall back on stereotypes and are bamboozled by atypical examples.  {81} 

In Words and Rules I aimed a microscope on a single phenomenon of language that has served as a test case for the ability of generic associative networks to account for the essence of language: assembling words, or pieces of words, into new combinations. People don't just memorize snatches of language but create new ones. A simple example is the English past tense. Given a neologism like to spam or to snarf, people don't have to run to the dictionary to look up their past-tense forms; they instinctively know that they are spammed and snarfed. The talent for assembling new combinations appears as early as age two, when children overapply the past-tense suffix to irregular verbs, as in We holded the baby rabbits and Horton heared a Who.¹⁶

The obvious way to explain this talent is to appeal to two kinds of computational operations in the mind. Irregular forms like held and heard are stored in and retrieved from memory, just like any other word. Regular forms like walk-walked can be generated by a mental version of the grammatical rule “Add -ed to the verb.” The rule can apply whenever memory fails. It may be used when a word is unfamiliar and no past-tense form had been stored in memory, as in to spam, and it may be used by children when they cannot recall an irregular form like heard and need some way of marking its tense. Combining a suffix with a verb is a small example of an important human talent: combining words and phrases to create new sentences and thereby express new thoughts. It is one of the new ideas of the cognitive revolution introduced in Chapter 3, and one of the logical challenges for connectionism I listed in the preceding discussion.

Connectionists have used the past tense as a proving ground to see if they could duplicate this textbook example of human creativity without using a rule and without dividing the labor between a system for memory and a system for grammatical combination. A series of computer models have tried to generate past-tense forms using simple pattern associator networks. The networks typically connect the sounds in verbs with the sounds in the past-tense form: -am with -ammed, -ing with -ung, and so on. The models can then generate new forms by analogy, just like the generalization from tigers to lions: trained on crammed, a model can guess spammed; trained on folded, it tends to say holded.

But human speakers do far more than associate sounds with sounds, and the models thus fail to do them justice. The failures come from the absence of machinery to handle logical relationships. Most of the models are baffled by new words that sound different from familiar words and hence cannot be generalized by analogy. Given the novel verb to frilg, for example, they come up not with frilged, as people do, but with an odd mishmash like freezled. That is because they lack the device of a variable, like x in algebra or “verb” in grammar, which can apply to any member of a category, regardless of how familiar  {82}  its properties are. (This is the gadget that allows people to engage in categorical rather than fuzzy reasoning.) The networks can only associate bits of sound with bits of sound, so when confronted with a new verb that does not sound like anything they were trained on, they assemble a pastiche of the most similar sounds they can find in their network.

The models also cannot properly distinguish among verbs that have the same sounds but different past-tense forms, such as ring the bell-rang the bell and ring the city-ringed the city. That is because the standard models represent only sound and are blind to the grammatical differences among verbs that call for different conjugations. The key difference here is between simple roots like ring in the sense of “resonate” (past tense rang) and complex verbs derived from nouns like ring in the sense of “form a ring around” (past tense ringed). To register that difference, a language-using system has to be equipped with compositional data structures (such as “a verb made from the noun ring”) and not just a beanbag of units.

Yet another problem is that connectionist networks track the statistics of the input closely: how many verbs of each sound pattern they have encountered. That leaves them unable to account for the epiphany in which young children discover the -ed rule and start making errors like holded and heared. Connectionist modelers can induce these errors only by bombarding the network with regular verbs (so as to burn in the -ed) in a way that is unlike anything real children experience. Finally, a mass of evidence from cognitive neuroscience shows that grammatical combination (including regular verbs) and lexical lookup (including irregular verbs) are handled by different systems in the brain rather than by a single associative network.

It's not that neural networks are incapable of handling the meanings of sentences or the task of grammatical conjugation. (They had better not be, since the very idea that thinking is a form of neural computation requires that some kind of neural network duplicate whatever the mind can do.) The problem lies in the credo that one can do everything with a generic model as long as it is sufficiently trained. Many modelers have beefed up, retrofitted, or combined networks into more complicated and powerful systems. They have dedicated hunks of neural hardware to abstract symbols like “verb phrase” and “proposition” and have implemented additional mechanisms (such as synchronized firing patterns) to bind them together in the equivalent of compositional, recursive symbol structures. They have installed banks of neurons for words, or for English suffixes, or for key grammatical distinctions. They have built hybrid systems, with one network that retrieves irregular forms from memory and another that combines a verb with a suffix.¹⁷

A system assembled out of beefed-up subnetworks could escape all the criticisms. But then we would no longer be talking about a generic neural network! We would be talking about a complex system innately tailored to  {83}  compute a task that people are good at. In the children's story called “Stone Soup,” a hobo borrows the use of a woman's kitchen ostensibly to make soup from a stone. But he gradually asks for more and more ingredients to balance the flavor until he has prepared a rich and hearty stew at her expense. Connectionist modelers who claim to build intelligence out of generic neural networks without requiring anything innate are engaged in a similar business. The design choices that make a neural network system smart — what each of the neurons represents, how they are wired together, what kinds of networks are assembled into a bigger system, in which way — embody the innate organization of the part of the mind being modeled. They are typically hand-picked by the modeler, like an inventor rummaging through a box of transistors and diodes, but in a real brain they would have evolved by natural selection (indeed, in some networks, the architecture of the model does evolve by a simulation of natural selection).¹⁸ The only alternative is that some previous episode of learning left the networks in a state ready for the current learning, but of course the buck has to stop at some innate specification of the first networks that kick off the learning process.

So the rumor that neural networks can replace mental structure with statistical learning is not true. Simple, generic networks are not up to the demands of ordinary human thinking and speaking; complex, specialized networks are a stone soup in which much of the interesting work has been done in setting up the innate wiring of the network. Once this is recognized, neural network modeling becomes an indispensable complement to the theory of a complex human nature rather than a replacement for it.¹⁹ It bridges the gap between the elementary steps of cognition and the physiological activity of the brain and thus serves as an important link in the long chain of explanation between biology and culture.

~

FOR MOST OF its history, neuroscience was faced with an embarrassment: the brain looked as if it were innately specified in every detail. When it comes to the body, we can see many of the effects of a person's life experience: it may be tanned or pale, callused or soft, scrawny or plump or chiseled. But no such marks could be found in the brain. Now, something has to be wrong with this picture. People learn, and learn massively: they learn their language, their culture, their know-how, their database of facts. Also, the hundred trillion connections in the brain cannot possibly be specified individually by a 750-megabyte genome. The brain somehow must change in response to its input; the only question is how.

We are finally beginning to understand how. The study of neural plasticity is hot. Almost every week sees a discovery about how the brain gets wired in the womb and tuned outside it. After all those decades in which no one could find anything that changed in the brain, it is not surprising that the  {84}  discovery of plasticity has given the nature-nurture pendulum a push. Some people describe plasticity as a harbinger of an expansion of human potential in which the powers of the brain will be harnessed to revolutionize childrearing, education, therapy, and aging. And several manifestos have proclaimed that plasticity proves that the brain cannot have any significant innate organization.²⁰ In Rethinking Innateness, Jeffrey Elman and a team of West Pole connectionists write that predispositions to think about different things in different ways (language, people, objects, and so on) may be implemented in the brain only as “attention-grabbers” that ensure that the organism will receive “massive experience of certain inputs prior to subsequent learning.”²¹ In a “constructivist manifesto,” the theoretical neuroscientists Stephen Quartz and Terrence Sejnowski write that “although the cortex is not a tabula rasa ... it is largely equipotential at early stages,” and therefore that innatist theories “appear implausible.”²²

Neural development and plasticity unquestionably make up one of the great frontiers of human knowledge. How a linear string of DNA can direct the assembly of an intricate three-dimensional organ that lets us think, feel, and learn is a problem to stagger the imagination, to keep neuroscientists engaged for decades, and to belie any suggestion that we are approaching “the end of science.”

And the discoveries themselves are fascinating and provocative. The cerebral cortex (outer gray matter) of the brain has long been known to be divided into areas with different functions. Some represent particular body parts; others represent the visual field or the world of sound; still others concentrate on aspects of language or thinking. We now know that with learning and practice some of their boundaries can move around. (This does not mean that the brain tissue literally grows or shrinks, only that if the cortex is probed with electrodes or monitored with a scanner, the boundary where one ability leaves off and the next one begins can shift.) Violinists, for example, have an expanded region of cortex representing the fingers of the left hand.²³ If a person or a monkey is trained on a simple task like recognizing shapes or attending to a location in space, neuroscientists can watch as parts of the cortex, or even individual neurons, take on the job.²⁴

The reallocation of brain tissue to new tasks is especially dramatic when people lose the use of a sense or body part. Congenitally blind people use their visual cortex to read Braille.²⁵ Congenitally deaf people use part of their auditory cortex to process sign language.²⁶ Amputees use the part of the cortex formerly serving the missing limb to represent other parts of their bodies.²⁷ Young children can grow up relatively normal after traumas to the brain that would turn adults into basket cases — even removal of the entire left hemisphere, which in adults underlies language and logical reasoning.²⁸ All this  {85}  suggests that the allocation of brain tissue to perceptual and cognitive processes is not done permanently and on the basis of the exact location of the tissue in the skull, but depends on how the brain itself processes information.

This dynamic allocation of tissue can also be seen as the brain puts itself together in the womb. Unlike a computer that gets assembled in a factory and is turned on for the first time when complete, the brain is active while it is being assembled, and that activity may take part in the assembly process. Experiments on cats and other mammals have shown that if a brain is chemically silenced during fetal development it may end up with significant abnormalities.²⁹ And patches of cortex develop differently depending on the kind of input they receive. In an experimental tour de force, the neuroscientist Mriganka Sur literally rewired the brains of ferrets so that signals from their eyes fed into the primary auditory cortex, the part of the brain that ordinarily receives signals from the ears.³⁰ When he then probed the auditory cortex with electrodes, he found that it acted in many ways like the visual cortex. Locations in the visual field were laid out like a map, and individual neurons responded to lines and stripes at a particular orientation and direction of movement, similar to the neurons in an ordinary visual cortex. The ferrets could even use their rewired brains to move toward objects that were detectable by sight alone. The input to the sensory cortex must help to organize it: visual input makes the auditory cortex work something like the visual cortex.

What do these discoveries mean? Do they show that the brain is “able to be shaped, molded, modeled, or sculpted,” as the dictionary definition of plastic would suggest? In the rest of this chapter I will show you that the answer is no.³¹ Discoveries of how the brain changes with experience do not show that learning is more powerful than we thought, that the brain can be dramatically reshaped by its input, or that the genes do not shape the brain. Indeed, demonstrations of the plasticity of the brain are less radical than they first appear: the supposedly plastic regions of cortex are doing pretty much the same thing they would have been doing if they had never been altered. And the most recent discoveries on brain development have refuted the idea that the brain is largely plastic. Let me go over these points in turn.

The fact that the brain changes when we learn is not, as some have claimed, a radical discovery with profound implications for nature and nurture or human potential. Dmitri Karamazov could have deduced it in his nineteenth-century prison cell as he mulled over the fact that thinking comes from quivering nerve tails rather than an immaterial soul. If thought and action are products of the physical activity of the brain, and if thought and action can be affected by experience, then experience has to leave a trace in the physical structure of the brain.  {86} 

So there is.no scientific question as to whether experience, learning, and practice affect the brain; they surely do if we are even vaguely on the right track. It is not surprising that people who can play the violin have different brains from those who cannot, or that masters of sign language or of Braille have different brains from people who speak and read. Your brain changes when you are introduced to a new person, when you hear a bit of gossip, when you watch the Oscars, when you polish your golf stroke — in short, whenever an experience leaves a trace in the mind. The only question is how learning affects the brain. Are memories stored in protein sequences, in new neurons or synapses, or in changes in the strength of existing synapses? When someone learns a new skill, is it stored only in organs dedicated to learning skills (like the cerebellum and the basal ganglia), or does it also adjust the cortex? Does an increase in dexterity depend on using more square centimeters of cortex or on using a greater concentration of synapses in the same number of square centimeters? These are important scientific problems, but they say nothing about whether people can learn, or how much. We already knew trained violinists play better than beginners or we would never have put their heads in the scanner to begin with. Neural plasticity is just another name for learning and development, described at a different level of analysis.

All this should be obvious, but nowadays any banality about learning can be dressed up in neurospeak and treated like a great revelation of science. According to a New York Times headline, “Talk therapy, a psychiatrist maintains, can alter the structure of the patient's brain.”³² I should hope so, or else the psychiatrist would be defrauding her clients. “Environmental manipulation can change the way [a child's] brain develops,” the pediatric neurologist Harry Chugani told the Boston Globe. “A child surrounded by aggression, violence, or inadequate stimulation will reflect these connections in the brain and behavior.”³³ Well, yes; if the environment affects the child at all, it would do so by changing connections in the brain. A special issue of the journal Educational Technology and Society was intended “to examine the position that learning takes place in the brain of the learner, and that pedagogies and technologies should be designed and evaluated on the basis of the effect they have on student brains.” The guest editor (a biologist) did not say whether the alternative was that learning takes place in some other organ of the body like the pancreas or that it takes place in an immaterial soul. Even professors of neuroscience sometimes proclaim “discoveries” that would be news only to believers in a ghost in the machine: “Scientists have found that the brain is capable of altering its connections...... You have the ability to change the synaptic connections within the brain.”³⁴ Good thing, because otherwise we would be permanent amnesiacs.

This neuroscientist is an executive at a company that “uses brain research  {87}  and technology to develop products intended to enhance human learning and performance,” one of many new companies with that aspiration. “The human being has unlimited creativity if focused and nurtured properly,” says a consultant who teaches clients to draw diagrams that “map their neural patterns.” “The older you get, the more connections and associations your brain should be making,” said a satisfied customer; “Therefore you should have more information stored in your brain. You just need to tap into it.”³⁵ Many people have been convinced by the public pronouncements of neuroscience advocates — on the basis of no evidence whatsoever — that varying the route you take when driving home can stave off the effects of aging.³⁶ And then there is the marketing genius who realized that blocks, balls, and other toys “provide visual and tactile stimulation” and “encourage movement and tracking,” part of a larger movement of “brain-based” childrearing and education that we will meet again in the chapter on children.³⁷

These companies tap into people's belief in a ghost in the machine by implying that any form of learning that affects the brain (as opposed, presumably, to the kinds of learning that don't affect the brain) is unexpectedly real or deep or powerful. But this is mistaken. All learning affects the brain. It is undeniably exciting when scientists make a discovery about how learning affects the brain, but that does not make the learning itself any more pervasive or profound.

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A second misinterpretation of neural plasticity can be traced to the belief that there is nothing in the mind that was not first in the senses. The most highly publicized discoveries about cortical plasticity concern primary sensory cortex, the patches of gray matter that first receive signals from the senses (via the thalamus and other subcortical organs). Writers who use plasticity to prop up the Blank Slate assume that if primary sensory cortex is plastic, the rest of the brain must be even more plastic, because the mind is built out of sensory experience. For example, one neuroscientist was quoted as saying that Sur's rewiring experiments “challenge the recent emphasis on the power of the genes” and “will push people back toward more consideration of environmental factors in creating normal brain organization.”³⁸

But if the brain is a complex organ with many parts, the moral does not follow. Primary sensory cortex is not the bedrock of the mind but a gadget, one of many in the brain, that happens to be specialized for certain kinds of signal processing in the first stages of sensory analysis. Let's suppose that primary sensory cortex really were formless, getting all its structure from the input. Would that mean that the entire brain is formless and gets all of its structure from the input? Not at all. For one thing, even primary sensory cortex is just one part of a huge, intricate system. To put things in perspective, here is a recent diagram of the wiring of the primate visual system:³⁹  {88} 

Primary visual cortex is the box near the bottom labeled “V1.” It is one of at least fifty distinct brain areas devoted to visual processing, and they are interconnected in precise ways. (Despite the spaghetti-like appearance, not everything is connected to everything else. Only about a third of the logically possible connections between components are actually present in the brain.) Primary visual cortex, by itself, is not enough to see with. Indeed, it is so deeply buried in the visual system that Francis Crick and the neuroscientist Christof Koch have argued that we are not conscious of anything that goes on in it.⁴⁰ What we see — familiar colored objects arranged in a scene or moving in  {89}  particular ways — is a product of the entire contraption. So even if the innards of the V1 box were completely specified by its input, we would have to explain the architecture of the rest of the visual system — the fifty boxes and their connections. I don't mean to imply that the entire block diagram is genetically specified, but much of it almost certainly is.⁴¹

And of course the visual system itself must be put into perspective, because it is just one part of the brain. The visual system dominates some half-dozen of the more than fifty major areas of the cortex that can be distinguished by their anatomy and connections. Many of the others underlie other functions such as language, reasoning, planning, and social skills. Though no one knows to what extent they are genetically prepared for their computational roles, there are hints that the genetic influence is substantial.⁴² The divisions are established in the womb, even if the cortex is cut off from sensory input during development. As development proceeds, different sets of genes are activated in different regions. The brain has a well-stocked toolbox of mechanisms to interconnect neurons, including molecules that attract or repel axons (the output fibers of neurons) to guide them to their targets, and molecules that glue them in place or ward them away. The number, size, and connectivity of cortical areas differ among species of mammals, and they differ between humans and other primates. This diversity is caused by genetic changes in the course of evolution that are beginning to be understood.⁴³ Geneticists recently discovered, for example, that different sets of genes are activated in the developing brain of humans and the developing brains of chimpanzees.⁴⁴

The possibility that cortical areas are specialized for different tasks has been obscured by the fact that different parts of the cortex look similar under a microscope. But because the brain is an information-processing system, that means little. The microscopic pits on a CD look the same regardless of what is recorded on it, and the strings of characters in different books look the same to someone who cannot read them. In an information-carrying medium, the content lies in combinatorial patterns among the elements — in the case of the brain, the details of the microcircuitry — and not in their physical appearance.

And the cortex itself is not the entire brain. Tucked beneath the cortex are other brain organs that drive important parts of human nature. They include the hippocampus, which consolidates memory and supports mental maps, the amygdala, which colors experience with certain emotions, and the hypothalamus, which originates sexual desire and other appetites. Many neuroscientists, even when they are impressed by the plasticity of the cortex, acknowledge that subcortical structures are far less plastic.⁴⁵ This is not a minor cavil about anatomy. Some commentators have singled out evolutionary psychology as a casualty of neural plasticity, saying that the changeability of the cortex proves that the brain cannot support evolutionary specializations.⁴⁶ But most proposals in evolutionary psychology are about drives like fear, sex, love, and  {90}  aggression, which reside largely in subcortical circuitry. More generally, on anyone's theory an innately shaped human ability would have to be implemented in a network of cortical and subcortical areas, not in a single patch of sensory cortex.

~

Another basic point about the brain has been lost in the recent enthusiasm for plasticity. A discovery that neural activity is crucial for brain development does not show either that learning is crucial in shaping the brain or that genes fail to shape the brain.

The study of neural development is often framed in terms of nature and nurture, but it is more fruitful to think of it as a problem in developmental biology — how a ball of identical cells differentiates into a functioning organ. Doing so stands the conventional assumptions of associationism on their head. Primary sensory cortex, rather than being the firmest part of the brain on top of which successive stories can only be even more plastic, may be the part of the brain that is most dependent on the input for proper development.

In assembling a brain, a complete genetic blueprint is out of the question for two reasons. One is that a gene cannot anticipate every detail of the environment, including the environment consisting of the other genes in the genome. It has to specify an adaptive developmental program that ensures that the organism as a whole functions properly across variations in nutrition, other genes, growth rates over the lifespan, random perturbations, and the physical and social environment. And that requires feedback from the way the rest of the organism is developing.

Take the development of the body. The genes that build a femur cannot specify the exact shape of the ball on top, because the ball has to articulate with the socket in the pelvis, which is shaped by other genes, nutrition, age, and chance. So the ball and the socket adjust their shapes as they rotate against each other while the baby kicks in the womb. (We know this because experimental animals that are paralyzed while they develop end up with grossly deformed joints.) Similarly, the genes shaping the lens of the growing eye cannot know how far back the retina is going to be or vice versa. So the brain of the baby is equipped with a feedback loop that uses signals about the sharpness of the image on the retina to slow down or speed up the physical growth of the eyeball. These are good examples of “plasticity,” but the metaphor of plastic material is misleading. The mechanisms are not designed to allow variable environments to shape variable organs. They do the opposite: they ensure that despite variable environments, a constant organ develops, one that is capable of doing its job.

Like the body, the brain must use feedback circuits to shape itself into a working system. This is especially true in the sensory areas, which have to cope with growing sense organs. For that reason alone we would expect the activity  {91}  of the brain to play a role in its own development, even if its end state, like those of the femur and the eyeball, is in some sense genetically specified. How this happens is still largely a mystery, but we know that patterns of neural stimulation can trigger the expression of a gene and that one gene can trigger many others.⁴⁷ Since every brain cell contains a complete genetic program, the machinery exists, in principle, for neural activity to trigger the development of an innately organized neural circuitry in any of several different regions. If so, brain activity would not be sculpting the brain; it would merely be telling the genome where in the brain a certain neural circuit should go.

So even an extreme innatist need not believe that the brain differentiates itself by the equivalent of GPS coordinates in the skull, following rules like “If you are between the left temple and the left ear, become a language circuit” (or a fear circuit, or a circuit for recognizing faces). A developmental program may be triggered in a part of the developing brain by some combination of the source of the stimulation, the firing pattern, the chemical environment, and other signals. The end result may be a faculty that is seated in different parts of the brain in different people. After all, the brain is the organ of computation, and the same computation can happen in different places as long as the pattern of information flow is the same. In your computer, a file or program may sit in different parts of memory or be fragmented across different sectors of the disk and work the same way in every case. It would not be surprising if the growing brain were at least that dynamic in allocating neural resources to computational demands.

The other reason that brains can't rely on a complete genetic blueprint is that the genome is a limited resource. Genes are constantly mutating over evolutionary time, and natural selection can weed out the bad ones only slowly. Most evolutionary biologists believe that natural selection can support a genome that is only so big. That means that the genetic plans for a complex brain have to be compressed to the minimum size that is consistent with the brain's developing and working properly. Though more than half the genome is put to work primarily or exclusively in the brain, that is not nearly enough to specify the brain's connection diagram.

The development program for the brain has to be resourceful. Take the problem of getting every axon (output fiber) from the eyes to connect to the brain in an orderly way. Neighboring points in the eye must connect to neighboring points in the brain (an arrangement called topographic mapping), and corresponding locations in the two eyes should end up near each other in the brain but not get mixed up with each other.

Rather than give each axon a genetically specified address, the mammalian brain may organize the connections in a cleverer way. In her studies of brain development in cats, the neuroscientist Carla Shatz has discovered that waves of activity flow across each retina, first in one direction, then in some other  {92}  direction.⁴⁸ That means that neurons that are next to each other in a single eye will tend to fire at around the same time, because they are often hit by the same wavefront. But axons from different eyes, or from distant locations in the same eye, will be uncorrelated in their activity, because a wave passing over one will miss the other. Just as you could reconstruct the seating diagram of a stadium if the fans were doing “the wave” along various directions and you knew only who stood up at which time (since people who stood up at the same time had to be seated near each other), the brain could reconstruct the spatial layout of the two eyes by listening for which sets of input neurons were firing at the same time. One of the rules of learning in neural networks, first outlined by the psychologist D. O. Hebb, is that “neurons that fire together wire together; neurons out of synch fail to link.” As the waves crisscross the retina for days and weeks, the visual thalamus downstream could organize itself into layers, each from a single eye, with adjacent neurons responding to adjacent parts of the retina. The cortex, in theory, could organize its wiring in a similar way.⁴⁹

Which parts of the brain actually use this auto-installation technique is another matter. The visual system does not appear to need the technique to grow topographically organized wiring; a rough topographic map develops under the direct control of the genes. Some neuroscientists believe that the fire-together-wire-together technique may still be used to make the maps more precise or to segregate the inputs from the two eyes.⁵⁰ That, too, has been challenged, but let us assume it is correct and see what it means.

The fire-together-wire-together process could, in theory, be set in motion by letting the eyeballs gaze at the world. The world has lines and edges that stimulate neighboring parts of the retina at the same time, and that provides the information the brain needs to set up or fine-tune an orderly map. But in the case of Shatz's cats, it works without any environmental input at all. The visual system develops in the pitch-dark womb, before the animal's eyes are open and before its rods and cones are even hooked up and functioning. The retinal waves are generated endogenously by the tissues of the retina during the period in which the visual brain has to wire itself up. In other words, the eye generates a test pattern, and the brain uses it to complete its own assembly. Ordinarily, axons from the eye carry information about things in the world, but the developmental program co-opted those axons to carry information about which neurons come from the same eye or the same place in the eye. A rough analogy occurred to me when I watched the cable TV installer figure out which cable in the basement led to a particular room upstairs. He attached a tone generator called a “screamer” to the end in the bedroom and then ran downstairs to listen for the signal on each cable in the bouquet coming out of the wall. Though the cables were designed to carry a television signal upstairs, not a test tone downstairs, they lent themselves to this other use during the installation process because an information conduit is useful for both purposes.  {93} 

The moral is that a discovery that brain development depends on brain activity may say nothing about learning or experience, only that the brain takes advantage of its own information-transmission abilities while wiring itself up.

Fire-together-wire-together is a trick that solves a particular kind of wiring problem: connecting a surface of receptors to a maplike representation in the cortex. The problem is found not just in the visual system but in other spatial senses such as touch. That is because the problem of tiling a patch of primary visual cortex, which receives information from the 2-D surface of the retina, is similar to the problem of tiling a patch of primary somatosensory cortex, which receives information from the 2-D surface of the skin. Even the auditory system may use the trick, because the inputs representing different sound frequencies (roughly, pitches) originate in a 1-D membrane in the inner ear, and the brain treats pitch in audition the way it treats space in vision and touch.

But the trick may be useless elsewhere in the brain. The olfactory (smell) system, for example, wires itself by a completely different technique. Unlike sights, sounds, and touches, which are arranged by location when they arrive at the sensory cortex, smells arrive all mixed together, and they are analyzed in terms of the chemical compounds making them up, each detected by a different receptor in the nose. Each receptor connects to a neuron that carries its signal into the brain, and in this case the genome really does use a different gene for each axon when wiring them into their respective places in the brain, a thousand genes in all. It economizes on genes in a remarkable way. The protein produced by each gene is used twice: once in the nose, as a receptor to detect an airborne chemical, and a second time in the brain, as a probe at the end of the corresponding axon to direct it to its proper spot in the olfactory bulb.⁵¹

The wiring problems are different again for other parts of the brain, such as the medulla, which generates the swallowing reflex and other fixed action patterns; the amygdala, which handles fear and other emotions; and the ventromedial frontal cortex, which is involved in social reasoning. The fire-together-wire-together technique may be an ideal method for sensory maps and other structures that simply have to reproduce redundancies in the world or in other parts of the brain, such as primary sensory cortex for seeing, touching, and hearing. But other regions evolved with different functions, such as smelling or swallowing or avoiding danger or winning friends, and they have to be wired by more complicated techniques. This is simply a corollary of the general point with which I began the chapter: the environment cannot tell the various parts of an organism what their goals are.

The doctrine of extreme plasticity has used the plasticity discovered in primary sensory cortex as a metaphor for what happens elsewhere in the brain. The upshot of these two sections is that it is not a very good metaphor. If the plasticity of sensory cortex symbolized the plasticity of mental life as a whole, it should be easy to change what we don't like about ourselves or other people.  {94} 

Take a case very different from vision, sexual orientation. Most gay men feel stirrings of attraction to other males around the time of the first hormonal changes that presage puberty. No one knows why some boys become gay — genes, prenatal hormones, other biological causes, and chance may all play a role — but my point is not so much about becoming gay as about becoming straight. In the less tolerant past, unhappy gay men sometimes approached psychiatrists (and sometimes were coerced into approaching them) for help in changing their sexual orientation. Even today, some religious groups pressure their gay members to “choose” heterosexuality. Many techniques have been foisted on them: psychoanalysis, guilt mongering, and conditioning techniques that use impeccable fire-together-wire-together logic (for example, having them look at Playboy centerfolds while sexually aroused). The techniques are all failures.⁵² With a few dubious exceptions (which are probably instances of conscious self-control rather than a change in desire), the sexual orientation of most gay men cannot be reversed by experience. Some parts of the mind just aren't plastic, and no discoveries about how sensory cortex gets wired will change that fact.

~

What is the brain actually doing when it undergoes the changes we call plasticity? One commentator called it “the brain equivalent of Christ turning water into wine” and thus a disproof of any theory that parts of the brain have been specialized for their jobs by evolution.⁵³ Those who don't believe in miracles are skeptical. Neural tissue is not a magical substance that can assume any form demanded of it but a mechanism that obeys the laws of cause and effect. When we take a closer look at the prominent examples of plasticity, we discover that the changes are not miracles after all. In every case, the altered cortex is not doing anything very different from what it ordinarily does.

Most demonstrations of plasticity involve remappings within primary sensory cortex. A brain area for an amputated or immobilized finger may be taken over by an adjacent finger, or a brain area for a stimulated finger expands its borders at the expense of a neighbor. The brain's ability to reweight its inputs is indeed remarkable, but the kind of information processing done by the taken-over cortex has not fundamentally changed: the cortex is still processing information about the surface of the skin and the angles of the joints. And the representation of a digit or part of the visual field cannot grow indefinitely, no matter how much it is stimulated; the intrinsic wiring of the brain would prevent it.⁵⁴

What about the takeover of the visual cortex by Braille in blind people? At first glance it looks like real transubstantiation. But maybe not. We are not witnessing just any talent taking over just any vacant lot in the cortex. Braille reading may use the anatomy of the visual cortex in the same way that seeing does.

Neuroanatomists have long known that there are as many fibers bringing  {95}  information down into the visual cortex from other brain areas as there are bringing information up from the eyes.⁵⁵ These top-down connections could have several uses. They may aim a spotlight of attention on portions of the visual field, or coordinate vision with the other senses, or group pixels into regions, or implement mental imagery, the ability to visualize things in the mind's eye.⁵⁶ Blind people may simply be using these prewired top-down connections to read Braille. They may be “imagining” the rows of dots as they feel them, much as a blindfolded person can imagine objects placed in his hand, though of course far more rapidly. (Previous research has established that blind people have mental images — perhaps even visual images — containing spatial information.)⁵⁷ The visual cortex is well suited to the kind of computation needed for Braille. In sighted people the eyes scan around a scene, bringing fine detail into the fovea, the high-resolution center of the retina. This is similar to moving the hands over a line of Braille, bringing fine detail under the high-resolution skin of the fingertips. So the visual system may be functioning in blind people much as it does in sighted ones, despite the lack of input from the eyes. Years of practice at imagining the tactile world and attending to the details of Braille have led the visual cortex to make maximal use of the innate inputs from other parts of the brain.

With deafness, too, one of the senses is taking over the controls of suitable circuitry, rather than just moving into any old unoccupied territory. Laura Petitto and her colleagues found that deaf people use the superior gyrus of the temporal lobe (a region near the primary auditory cortex) to recognize the elements of signs in sign languages, just as hearing people use it to process speech sounds in spoken languages. They also found that the deaf use the lateral prefrontal cortex to retrieve signs from memory, just as hearing people use it to retrieve words from memory.⁵⁸ This should come as no surprise. As linguists have long known, sign languages are organized much like spoken languages. They use words, a grammar, and even phonological rules that combine meaningless gestures into meaningful signs, just as phonological rules in spoken languages combine meaningless sounds into meaningful words.⁵⁹ Spoken languages, moreover, are partly modular: the representations for words and rules can be distinguished from the input-output systems that connect them to the ears and the mouth. The simplest interpretation, endorsed by Petitto and her colleagues, is that the cortical areas recruited in signers are specialized for language (words and rules), not for speech per se. What the areas are doing in deaf people is the same as what they are doing in hearing people.

Let me turn to the most amazing plasticity of all: the rewired ferrets whose eyes fed their auditory thalamus and cortex and made those areas work like a visual thalamus and cortex. Even here, water is not being turned into wine. Sur and his colleagues noted the redirected input did not change the actual wiring of the auditory brain, only the pattern of synaptic strengths. As a result they  {96}  found many differences between the co-opted auditory brain and a normal visual brain.⁶⁰ The representation of the visual field in the auditory brain was fuzzier and more disorganized, because the tissue is optimized for auditory, not visual, analysis. The map of the visual field, for instance, was far more precise in the left-right direction than in the up-down direction. That is because the left-right direction was mapped onto an axis of the auditory cortex that in normal animals represents different sound frequencies and thus gets inputs from the inner ear that are precisely arranged in order of frequency. But the up-down direction was mapped onto the perpendicular axis of the auditory cortex, which ordinarily gets a mass of inputs of the same frequency. Sur also notes that the connections between the primary auditory cortex and other brain areas for hearing (the equivalent of the wiring diagram for the visual system on page 88) were unchanged by the new input.

So patterns in the input can tune a patch of sensory cortex to mesh with that input, but only within the limits of the wiring already present. Sur suggests that the reason the auditory cortex in the rewired ferrets can process visual information at all is that certain kinds of signal processing may be useful to perform on raw sensory input, whether it is visual, auditory, or tactile:

On this view, one function of sensory thalamus or cortex is to perform certain stereotypical operations on input regardless of modality [vision, hearing, or touch]; the specific type of sensory input of course provides the substrate information that is transmitted and processed.... If the normal organization of central auditory structures is not altered, or at least not altered significantly, by visual input, then we might expect some operations similar to those we observe on visual inputs in operated ferrets to be carried out as well in the auditory pathway in normal ferrets. In other words, the animals with visual inputs induced into the auditory pathway provide a different window on some of the same operations that should occur normally in auditory thalamus and cortex.⁶¹

The suggestion that the auditory cortex is inherently suited to analyze visual input is not far-fetched. I mentioned that frequency (pitch) in hearing behaves a lot like space in vision. The mind treats soundmakers with different pitches as if they were objects at different locations, and it treats jumps in pitch like motions in space.⁶² This means that some of the analyses performed on sights may be the same as the analyses performed on sounds, and could be computed, at least in part, by similar kinds of circuitry. Inputs from an ear represent different frequencies; inputs from an eye represent spots at different locations. Neurons in the sensory cortex (both visual and auditory) receive information from a neighborhood of input fibers and extract simple patterns from them. Therefore neurons in the auditory cortex that ordinarily detect  {97}  rising or falling glides, rich or pure tones, and sounds that come from specific places may, in the rewired ferrets, automatically be capable of detecting lines of specific slants, places, and directions of movement.

This is not to say that the primary auditory cortex can handle visual input right out of the box. The cortex still must tune its synaptic connections in response to the patterns in the input. The rewired ferrets are a remarkable demonstration of how the developing sensory cortex organizes itself into a well-functioning system. But as in the other examples of plasticity, they do not show that input from the senses can transform an amorphous brain into doing whatever would come in handy. The cortex has an intrinsic structure that allows it to perform certain kinds of computation. Many examples of “plasticity” may consist of making the input mesh with that structure.

~

Anyone who has watched the Discovery Channel has seen footage of baby wildebeests or zebras falling out of the birth canal, wobbling on shaky legs for a minute or two, and then prancing around their mothers with their senses, drives, and motor control fully operational. It happens far too quickly for patterned experience to have organized their brains, so there must be genetic mechanisms capable of shaping the brain before birth. Neuroscientists were aware of this before plasticity came into vogue. The first studies of the development of the visual system by David Hubel and Torsten Wiesel showed that the microcircuitry of monkeys is pretty much complete at birth.⁶³ Even their famous demonstrations that the visual systems of cats can be altered by experience during a critical period of development (by being reared in the dark, in striped cylinders, or with one eye sewn shut) show only that experience is necessary to maintain the visual system and to retune it as the animal grows. They do not show that experience is necessary to wire up the brain to start with.

We know in a general way how the brain assembles itself under the guidance of the genes.⁶⁴ Even before the cortex has been formed, the neurons destined to make up different areas are organized into a"proto-map.” Each area in the proto-map is composed of neurons with different properties, molecular mechanisms that attract different input fibers, and different patterns of responses to the input. Axons are attracted and repelled by many kinds of molecules dissolved in the surrounding fluid or attached to the membranes of neighboring cells. And different sets of genes are expressed in different parts of the growing cortex. The neuroscientist Lawrence Katz has lamented that fire-together-wire-together has become a “dogma” keeping neuroscientists from exploring the full reach of these genetic mechanisms.⁶⁵

But the tide is beginning to turn, and recent discoveries are showing how parts of the brain can organize themselves without any information from the senses. In experiments that the journal Science called “heretical,” Katz's team removed one or both eyes from a developing ferret, depriving the visual cortex  {98}  of all its input. Nonetheless, the visual cortex developed with the standard arrangement of connections from the two eyes.⁶⁶

Genetically engineered mice have provided especially important clues, because knocking out a single gene can be more precise than the conventional techniques of poisoning neurons or slicing up the brain. One team invented a mouse whose synapses were completely shut down, preventing neurons from signaling to one another. Its brain developed fairly normally, complete with layered structures, fiber pathways, and synapses in the right places.⁶⁷ (The brain degenerated quickly after birth, showing again that neural activity may be more important in maintaining the brain than in wiring it.) Another team designed a mouse with a useless thalamus, depriving the entire cortex of its input. But the cortex differentiated into the normal layers and regions, each with a different set of turned-on genes.⁶⁸ A third study did the opposite, inventing mice that were missing one of the genes that lay down gradients of molecules that help organize the brain by triggering other genes in particular places. The missing gene made a big difference: the boundaries among cortical areas were badly warped.⁶⁹ The studies with knockout mice, then, suggest that genes may be more important than neural activity in organizing the cortex. Neural activity undoubtedly plays a role, which depends on the species, the stage of development, and the part of the brain, but it is just one capability of the brain rather than the source of its structure.

What about our own species? Recall that a recent study of twins showed that differences in the anatomy of the cortex, particularly the amount of gray matter in different cortical regions, are under genetic control, paralleling differences in intelligence and other psychological traits.⁷⁰ And demonstrations of the plasticity of the human brain do not rule out substantial genetic organization. One of the most commonly cited examples of plasticity in both humans and monkeys is that the cortex dedicated to an amputated or numbed body part may get reallocated to some other body part. But the fact that the input can change the brain once it is built does not mean that the input molded the brain in the first place. Most amputees experience phantom limbs: vivid, detailed hallucinations of the missing body part. Amazingly, a substantial proportion of people who were born with a limb missing experience these apparitions as well.⁷¹ They can describe the anatomy of their phantom limb (for example, how many toes they feel in a nonexistent foot) and may even feel that they are gesturing with their phantom hands during conversation. One girl solved arithmetic problems by counting on her phantom fingers! The psychologist Ronald Melzack, who documented many of these cases, proposed that the brain contains an innate “neuromatrix,” distributed across several cortical and subcortical regions, dedicated to representing the body.

The impression that human brains are limitlessly plastic has also come from demonstrations that children can sometimes recover from early brain  {99}  damage. But the existence of cerebral palsy — lifelong difficulties with motor control and speech caused by malformations or early damage in the brain — shows that even the plasticity of a child's brain has severe limits. The most famous evidence for extreme plasticity in humans had been the ability of some children to grow up relatively normal even with an entire hemisphere surgically removed in infancy.⁷² But that may be a special case, which arises from the fact that the primate brain is fundamentally a symmetrical organ. The typically human asymmetries — language more on the left, spatial attention and some emotions more on the right — are superimposed on that mostly symmetrical design. It would not be surprising if the hemispheres were genetically programmed with pretty much the same abilities, together with small biases that lead each hemisphere to specialize in some talents while letting others wither. With one hemisphere gone, the remaining one has to put all its capabilities to full use.

What happens when a child loses a part of the cortex in both hemispheres, so neither hemisphere can take over the job of the missing part in the other? If cortical regions are interchangeable, plastic, and organized by the input, then an intact part of the brain should take over the function of the missing parts. The child may be a bit slower because he is working with less brain tissue, but he should develop a full complement of human faculties. But that is not what seems to happen. Several decades ago, neurologists studied a boy who suffered a temporary loss of oxygen to the brain and lost both the standard language areas in the left hemisphere and their mirror images on the right. Though he was just ten days old when he sustained the damage, he grew into a child with permanent difficulties in speaking and understanding.⁷³

That case study, like many in pediatric neurology, is not scientifically pure, but recent studies on two other mental faculties echo the point that babies’ brains may be less plastic than many people think. The psychologist Martha Farah and her collaborators recently reported the case of a sixteen-year-old boy who contracted meningitis when he was one day old and suffered damage to the visual cortex and to the bottom of the temporal lobes on both sides of his brain.⁷⁴ When adults sustain such damage, they lose the ability to recognize faces and also have some trouble recognizing animals, though they often can recognize words, tools, furniture, and other shapes. The boy had exactly this syndrome. Though he grew up with normal verbal intelligence, he was utterly incapable of recognizing faces. He could not even recognize pictures of the cast of his favorite television show, Baywatch, which he had seen for an hour a day for the preceding year and a half. Without the appropriate strips of brain, sixteen years of seeing faces and plenty of available cortex were not enough to give him the basic human ability to recognize other people by sight.

The neuroscientists Steven Anderson, Hannah and Antonio Damasio, and their colleagues recently tested two young adults who had sustained damage to  {100}  their ventromedial and orbital prefrontal cortex when they were young children.⁷⁵ These are the parts of the brain that sit above the eyes and are important for empathy, social skills, and self-management (as we know from Phineas Gage, the railroad worker whose brain was impaled by a tamping iron). Both children recovered from their injuries and grew up with average IQs in stable homes with normal siblings and college-educated parents. If the brain were really homogeneous and plastic, the healthy parts should have been shaped by the normal social environment and taken oyer the functions of the damaged parts. But that is not what happened with either of the children. One, who had been run over by a car when she was fifteen months old, grew into an intractable child who ignored punishment and lied compulsively. As a teenager she shoplifted, stole from her parents, failed to win friends, showed no empathy or remorse, and was dangerously uninterested in her own baby. The other patient was a young man who had lost similar parts of his brain to a tumor when he was three months old. He too grew up friendless, shiftless, thieving, and hotheaded. Along with their bad behavior, both had trouble thinking through simple moral problems, despite having IQs in the normal range. They could not, for example, say what two people should do if they disagreed on which TV channel to watch, or decide whether a man ought to steal a drug to save his dying wife.

These cases do more than refute the doctrine of extreme plasticity. They set a challenge for the genetics and neuroscience of the twenty-first century. How does the genome tell a developing brain to differentiate into neural networks that are prepared for such abstract computational problems as recognizing a face or thinking about the interests of other people?

~

The Blank Slate has made its last stand, but, as we have seen, its latest scientific fortifications are illusory. The human genome may have a smaller number of genes than biologists had previously estimated, but that only shows that the number of genes in a genome has little to do with the complexity of the organism. Connectionist networks may explain some of the building blocks of cognition, but they are too underpowered to account for thought and language on their own; they must be innately engineered and assembled for the tasks. Neural plasticity is not a magical protean power of the brain but a set of tools that help turn megabytes of genome into terabytes of brain, that make sensory cortex dovetail with its input, and that implement the process called learning.

Therefore genomics, neural networks, and neural plasticity fit into the picture that has emerged in recent decades of a complex human nature. It is not, of course, a nature that is rigidly programmed, impervious to the input, free of culture, or endowed with the minutiae of every concept and feeling. But it is a nature that is rich enough to take on the demands of seeing, moving,  {101}  planning, talking, staying alive, making sense of the environment, and negotiating the world of other people.

The aftermath of the Blank Slate's last stand is a good time to take stock of the case for the alternative. Here is my summary of the evidence for a complex human nature, some of it reiterating arguments from previous chapters, some of it anticipating arguments in chapters to come.

Simple logic says there can be no learning without innate mechanisms to do the learning. Those mechanisms must be powerful enough to account for all the kinds of learning that humans accomplish. Learnability theory — the mathematical analysis of how learning can work in principle — tells us there are always an infinite number of generalizations that a learner can draw from a finite set of inputs.⁷⁶ The sentences heard by a child, for example, can be grounds for repeating them back verbatim, producing any combination of words with the same proportion of nouns to verbs, or analyzing the underlying grammar and producing sentences that conform to it. The sight of someone washing dishes can, with equal logical justification, prompt a learner to try to get dishes clean or to let warm water run over his fingers. A successful learner, then, must be constrained to draw some conclusions from the input and not others. Artificial intelligence reinforces this point. Computers and robots programmed to do humanlike feats are invariably endowed with many complex modules.⁷⁷

Evolutionary biology has shown that complex adaptations are ubiquitous in the living world, and that natural selection is capable of evolving them, including complex cognitive and behavioral adaptations.⁷⁸ The study of the behavior of animals in their natural habitat shows that species differ innately from one another in their drives and abilities, some of them (like celestial navigation and food caching) requiring complicated and specialized neural systems.⁷⁹ The study of humans from an evolutionary perspective has shown that many psychological faculties (such as our hunger for fatty food, for social status, and for risky sexual liaisons) are better adapted to the evolutionary demands of our ancestral environment than to the actual demands of the current environment.⁸⁰ Anthropological surveys have shown that hundreds of universals, pertaining to every aspect of experience, cut across the world's cultures.⁸¹

Cognitive scientists have discovered that distinct kinds of representations and processes are used in different domains of knowledge, such as words and rules for language, the concept of an enduring object for understanding the physical world, and a theory of mind for understanding other people.⁸² Developmental psychology has shown that these distinct modes of interpreting experience come on line early in life: infants have a basic grasp of objects, numbers, faces, tools, language, and other domains of human cognition.⁸³

The human genome contains an enormous amount of information, both in the genes and in the noncoding regions, to guide the construction of a  {102}  complex organism. In a growing number of cases, particular genes can be tied to aspects of cognition, language, and personality.⁸⁴ When psychological traits vary, much of the variation comes from differences in genes: identical twins are more similar than fraternal twins, and biological siblings are more similar than adoptive siblings, whether reared together or apart.⁸⁵ A person's temperament and personality emerge early in life and remain fairly constant throughout the lifespan.⁸⁶ And both personality and intelligence show few or no effects of children's particular home environments within their culture: children reared in the same family are similar mainly because of their shared genes.⁸⁷

Finally, neuroscience is showing that the brain's basic architecture develops under genetic control. The importance of learning and plasticity notwithstanding, brain systems show signs of innate specialization and cannot arbitrarily substitute for one another.⁸⁸

In these three chapters I have given you a summary of the current scientific case for a complex human nature. The rest of the book is about its implications.

FEAR AND LOATHING

B

y the middle of the second half of the twentieth century, the ideals of the social scientists of the first half had enjoyed a well-deserved victory. Eugenics, Social Darwinism, colonial conquest, Dickensian policies toward children, overt expressions of racism and sexism among the educated, and official discrimination against women and minorities had been eradicated, or at least were rapidly fading, from mainstream Western life.

At the same time, the doctrine of the Blank Slate, which had been blurred with ideals of equality and progress for much of the century, was beginning to show cracks. As the new sciences of human nature began to flourish, it was becoming clear that thinking is a physical process, that people are not psychological clones, that the sexes differ above the neck as well as below it, that the human brain was not exempt from the process of evolution, and that people in all cultures share mental traits that might be illuminated by new ideas in evolutionary biology.

These developments presented intellectuals with a choice. Cooler heads could have explained that the discoveries were irrelevant to the political ideals of equal opportunity and equal rights, which are moral doctrines on how we ought to treat people rather than scientific hypotheses about what people are like. Certainly it is wrong to enslave, oppress, discriminate against, or kill people regardless of any foreseeable datum or theory that a sane scientist would offer.

But it was not a time for cool heads. Rather than detach the moral doctrines from the scientific ones, which would ensure that the clock would not be turned back no matter what came out of the lab and field, many intellectuals, including some of the world's most famous scientists, made every effort to connect the two. The discoveries about human nature were greeted with fear and loathing because they were thought to threaten progressive ideals. All this could be relegated to the history books were it not for the fact that these intellectuals, who once called themselves radicals, are now the establishment, and  {104}  the dread they sowed about human nature has taken root in modern intellectual life.

This part of the book is about the politically motivated reactions to the new sciences of human nature. Though the opposition was originally a brainchild of the left, it is becoming common on the right, whose spokespeople are fired up by some of the same moral objections. In Chapter 6 I recount the shenanigans that erupted as a reaction to the new ideas about human nature. In Chapter 7 I show how these reactions came from a moral imperative to uphold the Blank Slate, the Noble Savage, and the Ghost in the Machine.

Chapter 6

Political Scientists

The first lecture I attended as a graduate student at Harvard in 1976 was by the famous computer scientist Joseph Weizenbaum. He was an early contributor to artificial intelligence (AI) and is best remembered for the program Eliza, which fooled people into thinking that the computer was conversing though it was just spouting canned repartee. Weizenbaum had just published Computer Power and Human Reason, a critique of artificial intelligence and computer models of cognition, praised as “the most important computer book of the past decade.” I had misgivings about the book, which was short on irgument and long on sanctimony. (For example, he wrote that certain ideas in artificial intelligence, such as a science-fiction proposal for a hybrid of nervous systems and computers, were “simply obscene. These are [applications] whose very contemplation ought to give rise to feelings of disgust in every civilized person.... One must wonder what must have happened to the proposers’ perception of life, hence to their perceptions of themselves as part of the continuum of life, that they can even think of such a thing.”)¹ Still, nothing could have prepared me for the performance in store at the Science Center that afternoon.

Weizenbaum discussed an AI program by the computer scientists Alan Newell and Herbert Simon that relied on analogy: if it knew the solution to one problem, it applied the solution to other problems with a similar logical structure. This, Weizenbaum told us, was really designed to help the Pentagon come up with counterinsurgency strategies in Vietnam. The Vietcong had been said to “move in the jungle as fish move in water.” If the program were fed this information, he said, it could deduce that just as you can drain a pond to expose the fish, you can denude the jungle to expose the Vietcong. Turning to research on speech recognition by computer, he said that the only conceivable reason to study speech perception was to allow the CIA to monitor millions of telephone conversations simultaneously, and he urged the students in the audience to boycott the topic. But, he added, it didn't really matter if we ignored  {106}  his advice because he was completely certain — there was not the slightest doubt in his mind — that by the year 2000 we would all be dead. And with that inspiring charge to the younger generation he ended the talk.

The rumors of our death turned out to be greatly exaggerated, and the other prophecies of the afternoon fared no better. The use of analogy in reasoning, far from being the work of the devil, is today a major research topic in cognitive science and is widely considered a key to what makes us smart. Speech-recognition software is routinely used in telephone information services and comes packaged with home computers, where it has been a godsend for the disabled and for people with repetitive strain injuries. And Weizenbaum's accusations stand as a reminder of the political paranoia and moral exhibitionism that characterized university life in the 1970s, the era in which the current opposition to the sciences of human nature took shape.

It was not how I imagined that scholarly discourse would be conducted in the Athens of America, but perhaps I should not have been surprised. Throughout history, battles of opinion have been waged by noisy moralizing, demonizing, hyperbole, and worse. Science was supposed to be a beachhead in which ideas rather than people are attacked and in which verifiable facts are separated from political opinions. But when science began to edge toward the topic of human nature, onlookers reacted differently from how they would to discoveries about, say, the origin of comets or the classification of lizards, and scientists reverted to the moralistic mindset that comes so naturally to our species.

Research on human nature would be controversial in any era, but the new sciences picked a particularly bad decade in which to attract the spotlight. In the 1970s many intellectuals had become political radicals. Marxism was correct, liberalism was for wimps, and Marx had pronounced that “the ruling ideas of each age have ever been the ideas of its ruling class.” The traditional misgivings about human nature were folded into a hard-left ideology, and scientists who examined the human mind in a biological context were now considered tools of a reactionary establishment. The critics announced they were part of a “radical science movement,” giving us a convenient label for the group.²

Weizenbaum was repelled by the attempt within artificial intelligence and cognitive science to unify mind and mechanism, but the other sciences of human nature evoked acrimony as well. In 1971 the psychologist Richard Herrnstein published an article called “IQ” in the Atlantic Monthly.³ Herrnstein's argument, he was the first to point out, should have been banal. He wrote that as social status becomes less strongly determined by arbitrary legacies such as race, parentage, and inherited wealth, it will become more strongly determined by talent, especially (in a modern economy) intelligence. Since differences in intelligence are partly inherited, and since intelligent people tend to marry other intelligent people, when a society becomes more just it  {107}  will also become more stratified along genetic lines. Smarter people will tend to float into the higher strata, and their children will tend to stay there. The basic argument should be banal because it is based on a mathematical necessity: as the proportion of variance in social status caused by nongenetic factors goes down, the proportion caused by genetic factors has to go up. It could be completely false only if there were no variation in social status based on intellectual talent (which would require that people not preferentially hire and trade with the talented) or if there were no genetic variation in intelligence which would require that people be either blank slates or clones).

Herrnstein's argument does not imply that any differences in average intelligence between races are innate (a distinct hypothesis that had been broached by the psychologist Arthur Jensen two years earlier),⁴ and he explicitly denied that he was making such a claim. School desegregation was less than a generation old, civil rights legislation less than a decade, so the differences that had been documented in average IQ scores of blacks and whites could easily be explained by differences in opportunity. Indeed, to say that Herrnstein's syllogism implied that black people would end up at the bottom of a genetically stratified society was to add the gratuitous assumption that blacks were on average genetically less intelligent, which Herrnstein took pains to avoid.

Nonetheless, the influential psychiatrist Alvin Poussaint wrote that Herrnstein “has become the enemy of black people and his pronouncements are a threat to the survival of every black person in America.” He asked rhetorically, “Shall we carry banners for Herrnstein proclaiming his right to freedom of speech?” Leaflets were handed out at Boston-area universities urging students to “Fight Harvard Prof's Fascist Lies,” and Harvard Square was plastered with his photograph above the caption wanted for racism and five misquotations purportedly from his article. Herrnstein received a death threat and found that he could no longer speak about his research specialty, learning in pigeons, because wherever he went the lecture halls were filled with chanting mobs. At Princeton, for example, students declared they would block the doors of the auditorium to force him to answer questions on the IQ controversy. Several lectures were canceled when the hosting universities said they could not guarantee his safety.⁵

The topic of innate differences among people has obvious political implications, which I will examine in later chapters. But some scholars were incensed by the seemingly warm-and-fuzzy claim that people have innate commonalities. In the late 1960s the psychologist Paul Ekman discovered that smiles, frowns, sneers, grimaces, and other facial expressions were displayed and understood worldwide, even among foraging peoples with no prior contact with the West. These findings, he argued, vindicated two claims that Darwin had made in his 1872 book The Expression of the Emotions in Man and  {108}  Animals. One was that humans had been endowed with emotional expressions by the process of evolution; the other, radical in Darwin's time, was that all races had recently diverged from a common ancestor.⁶ Despite these uplifting messages, Margaret Mead called Ekman's research “outrageous,” “appalling,” and “a disgrace” — and these were some of the milder responses.⁷ At the annual meeting of the American Anthropological Association, Alan Lomax Jr. rose from the audience shouting that Ekman should not be allowed to speak because his ideas were fascist. On another occasion an African American activist accused him of racism for claiming that black facial expressions were no different from white ones. (Sometimes you can't win.) And it was not just claims about innate faculties in the human species that drew the radicals’ ire, but claims about innate faculties in any species. When the neuroscientist Torsten Wiesel published his historic work with David Hubel showing that the visual system of cats is largely complete at birth, another neuroscientist angrily called him a fascist and vowed to prove him wrong.

~

Some of these protests were signs of the times and faded with the decline of radical chic. But the reaction to two books on evolution continued for decades and became part of the intellectual mainstream.

The first was E. O. Wilson's Sociobiology, published in 1975.⁸ Sociobiology synthesized a vast literature on animal behavior using new ideas on natural selection from George Williams, William Hamilton, John Maynard Smith, and Robert Trivers. It reviewed principles on the evolution of communication, altruism, aggression, sex, and parenting, and applied them to the major taxa of social animals such as insects, fishes, and birds. The twenty-seventh chapter did the same for Homo sapiens, treating our species like another branch of the animal kingdom. It included a review of the literature on universals and variation among societies, a discussion of language and its effects on culture, and the hypothesis that some universals (including the moral sense) may come from a human nature shaped by natural selection. Wilson expressed the hope that this idea might connect biology to the social sciences and philosophy, a forerunner of the argument in his later book Consilience.

The first attack on Sociobiology zeroed in on its main heresy. In a book-length critique, the anthropologist Marshall Sahlins defined “vulgar sociobiology” as the challenge to Durkheim's and Kroeber's doctrine of the superorganism: the belief that culture and society lived in a separate realm from individual people and their thoughts and feelings. “Vulgar sociobiology,” Sahlins wrote, “consists in the explication of human social behavior as the expression of the needs and drives of the human organism, such propensities having been constructed in human nature by biological evolution.”⁹ Acknowledging fear of an incursion into his academic turf, he added, “The central intellectual problem does come down to the autonomy of culture and of the  {109}  study of culture. Sociobiology challenges the integrity of culture as a thing-in-itself, as a distinctive and symbolic human creation.”¹⁰

Sahlins's book was called The Use and Abuse of Biology. An example of the alleged abuse was the idea that Hamilton's theory of inclusive fitness could help explain the importance of family ties in human life. Hamilton had shown how a tendency to make sacrifices for relatives could have evolved. Relatives share genes, so any gene that nudges an organism to help a relative would be indirectly helping a copy of itself. The gene will proliferate if the cost incurred by the favor is less than the benefit conferred to the relative, discounted by the degree of relatedness (one-half for a full sibling or offspring, one-eighth for a first cousin, and so on). That can't be true, Sahlins wrote, because people in most cultures don't have words for fractions. This leaves them unable to figure out the coefficients of relatedness that would tell them which relatives to favor and by how much. His objection is a textbook confusion of a proximate cause with an ultimate cause. It is like saying that people can't possibly see in depth, because most cultures haven't worked out the trigonometry that underlies stereoscopic vision.

In any case, “vulgar” wasn't the half of it. Following a favorable review in the New York Review of Books by the distinguished biologist C. H. Waddington, the “Sociobiology Study Group” (including two of Wilson's colleagues, the paleontologist Stephen Jay Gould and the geneticist Richard Lewontin) published a widely circulated philippic called “Against ‘Sociobiology.'” After lumping Wilson with proponents of eugenics, Social Darwinism, and Jensen's hypothesis of innate racial differences in intelligence, the signatories wrote:

The reason for the survival of these recurrent determinist theories is that they consistently tend to provide a genetic justification of the status quo and of existing privileges for certain groups according to class, race, or sex.... These theories provided an important basis for the enactment of sterilization laws and restrictive immigration laws by the United States between 1910 and 1930 and also for the eugenics policies which led to the establishment of gas chambers in Nazi Germany.

... What Wilson's book illustrates to us is the enormous difficulty in separating out not only the effects of environment (e.g., cultural transmission) but also the personal and social class prejudices of the researcher. Wilson joins the long parade of biological determinists whose work has served to buttress the institutions of their society by exonerating them from responsibility for social problems.¹¹

They also accused Wilson of discussing “the salutary advantages of genocide” and of making “institutions such as slavery... seem natural in human societies because of their ‘universal’ existence in the biological kingdom.” In  {110}  case the connection wasn't clear enough, one of the signatories wrote elsewhere that “in the last analysis it was sociobiological scholarship ... that provided the conceptual framework by which eugenic theory was transformed into genocidal practice” in Nazi Germany.¹²

One can certainly find things to criticize in the final chapter of Sociobiology. We now know that some of Wilson's universals are inaccurate or too coarsely stated, and his claim that moral reasoning will someday be superseded by evolutionary biology is surely wrong. But the criticisms in “Against ‘Sociobiology'” were demonstrably false. Wilson was called a “determinist,'” someone who believes that human societies conform to a rigid genetic formula. But this is what he had written:

The first and most easily verifiable diagnostic trait [about human societies] is statistical in nature. The parameters of social organization ... vary far more among human populations than among those of any other primate species.... Why are human societies this flexible?¹³

Similarly, Wilson was accused of believing that people are locked into castes determined by their race, class, sex, and individual genome. But in fact he had written that “there is little evidence of any hereditary solidification of status”¹⁴ and that “human populations are not very different from one another genetically.”¹⁵ Moreover:

Human societies have effloresced to levels of extreme complexity because their members have the intelligence and flexibility to play roles of virtually any degree of specification, and to switch them as the occasion demands. Modern man is an actor of many parts who may well be stretched to his limit by the constantly shifting demands of the environment.¹⁶

As for the inevitability of aggression — another dangerous idea he was accused of holding — what Wilson had written was that in the course of human evolution “aggressiveness was constrained and the old forms of primate dominance replaced by complex social skills.”¹⁷ The accusation that Wilson (a lifelong liberal Democrat) was led by personal prejudice to defend racism, sexism, inequality, slavery, and genocide was especially unfair — and irresponsible, because Wilson became a target of vilification and harassment by people who read the manifesto but not the book.¹⁸

At Harvard there were leaflets and teach-ins, a protester with a bullhorn calling for Wilson's dismissal, and invasions of his classroom by slogan-shouting students. When he spoke at other universities, posters called him the “Right-Wing Prophet of Patriarchy” and urged people to bring noisemakers to  {111}  his lectures.¹⁹ Wilson was about to speak at a 1978 meeting of the American Association for the Advancement of Science when a group of people carrying placards (one with a swastika) rushed onto the stage chanting, “Racist Wilson, you can't hide, we charge you with genocide.” One protester grabbed the microphone and harangued the audience while another doused Wilson with a pitcher of water.

As the notoriety of Sociobiology grew in the ensuing years, Hamilton and Trivers, who had thought up many of the ideas, also became targets of picketers, as did the anthropologists Irven DeVore and Lionel Tiger when they :ried to teach the ideas. The insinuation that Trivers was a tool of racism and right-wing oppression was particularly galling because Trivers was himself a political radical, a supporter of the Black Panthers, and a scholarly collaborator of Huey Newton's.²⁰ Trivers had argued that sociobiology is, if anything, a force for political progress. It is rooted in the insight that organisms did not evolve to benefit their family, group, or species, because the individuals making up those groups have genetic conflicts of interest with one another and would be selected to defend those interests. This immediately subverts the comfortable belief that those in power rule for the good of all, and it throws a spotlight on hidden actors in the social world, such as females and the younger generation. Also, by finding an evolutionary basis for altruism, sociobiology shows that a sense of justice has a deep foundation in people's minds and need not run against our organic nature. And by showing that self-deception is likely to evolve (because the best liar is the one who believes his own lies), sociobiology encourages self-scrutiny and helps undermine hypocrisy and corruption.²¹ (I will return to the political beliefs of Trivers and other “Darwinian leftists” in the chapter on politics.)

Trivers later wrote of the attacks on sociobiology, “Although some of the attackers were prominent biologists, the attack seemed intellectually feeble and lazy. Gross errors in logic were permitted as long as they appeared to give some tactical advantage in the political struggle.... Because we were hirelings of the dominant interests, said these fellow hirelings of the same interests, we were their mouthpieces, employed to deepen the [deceptions] with which the ruling elite retained their unjust advantage. Although it follows from evolutionary reasoning that individuals will tend to argue in ways that are ultimately (sometimes unconsciously) self-serving, it seemed a priori unlikely that evil should reside so completely in one set of hirelings and virtue in the other.”²²

The “prominent biologists” that Trivers had in mind were Gould and Lewontin, and together with the British neuroscientist Steven Rose they became the intellectual vanguard of the radical science movement. For twenty-five years they have indefatigably fought a rearguard battle against behavioral genetics, sociobiology (and later evolutionary psychology), and the neuro-science of politically sensitive topics such as sex differences and mental  {112}  illness.²³ Other than Wilson, the major target of their attacks has been Richard Dawkins. In his 1976 book The Selfish Gene, Dawkins covered many of the same ideas as Wilson but concentrated on the logic of the new evolutionary theories rather than the zoological details. He said almost nothing about humans.

The radical scientists’ case against Wilson and Dawkins can be summed up in two words: “determinism” and “reductionism.”²⁴ Their writings are peppered with these words, used not in any technical sense but as vague terms of abuse. For example, here are two representative passages in a book by Lewontin, Rose, and the psychologist Leon Kamin with the defiantly Blank Slate title Not in Our Genes:

Sociobiology is a reductionist, biological determinist explanation of human existence. Its adherents claim ... that the details of present and past social arrangements are the inevitable manifestations of the specific action of genes.²⁵

[Reductionists] argue that the properties of a human society are ... no more than the sums of the individual behaviors and tendencies of the individual humans of which that society is composed. Societies are “aggressive” because the individuals who compose them are “aggressive,” for instance'.²⁶

The quotations from Wilson we saw earlier in the chapter show that he never expressed anything close to these ridiculous beliefs, and neither, of course, did Dawkins. For example, after discussing the tendency in mammals for males to seek a greater number of sexual partners than females do, Dawkins devoted a paragraph to human societies in which he wrote:

What this astonishing variety suggests is that man's way of life is largely determined by culture rather than by genes. However, it is still possible that human males in general have a tendency towards promiscuity, and females a tendency to monogamy, as we would predict on evolutionary grounds. Which of these tendencies wins in particular societies depends on details of cultural circumstance, just as in different animal species it depends on ecological details.²⁷

What exactly do “determinism” and “reductionism” mean? In the precise sense in which mathematicians use the word, a “deterministic” system is one whose states are caused by prior states with absolute certainty, rather than probabilistically. Neither Dawkins nor any other sane biologist would ever dream of proposing that human behavior is deterministic, as if people must  {113}  commit acts of promiscuity, aggression, or selfishness at every opportunity. Among the radical scientists and the many intellectuals they have influenced, “determinism” has taken on a meaning that is diametrically opposed to its true meaning. The word is now used to refer to any claim that people have a tendency to act in certain ways in certain circumstances. It is a sign of the tenacity of the Blank Slate that a probability greater than zero is equated with a probability of 100 percent. Zero innateness is the only acceptable belief, and all departures from it are treated as equivalent.

So much for genetic determinism. What about “reductionism” (a concept we examined in Chapter 4) and the claim that Dawkins is “the most reductionist of sociobiologists,” one who believes that every trait has its own gene? Lewontin, Rose, and Kamin try to educate their readers on how living things really work according to their alternative to reductionism, which they call “dialectical biology":

Think, for example, of the baking of a cake: the taste of the product is the result of a complex interaction of components — such as butter, sugar, and flour — exposed for various periods to elevated temperatures; it is not dissociable into such-or-such a percent of flour, such-or-such of butter, etc., although each and every component... has its contribution to make to the final product.²⁸

I will let Dawkins comment:

When put like that, this dialectical biology seems to make a lot of sense. Perhaps even / can be a dialectical biologist. Come to think of it, isn't there something familiar about that cake? Yes, here it is, in a 1981 publication by the most reductionist of sociobiologists:

“... If we follow a particular recipe, word for word, in a cookery book, what finally emerges from the oven is a cake. We cannot now break the cake into its component crumbs and say: this crumb corresponds to the first word in the recipe; this crumb corresponds to the second word in the recipe, etc. With minor exceptions such as the cherry on top, there is no one-to-one mapping from words of recipe to ‘bits’ of cake. The whole recipe maps onto the whole cake.”

I am not, of course, interested in claiming priority for the cake.... But what I do hope is that this little coincidence may at least give Rose and Lewontin pause. Could it be that their targets are not quite the naïvely atomistic reductionists they would desperately like them to be?²⁹

Indeed, the accusation of reductionism is topsy-turvy because Lewontin and Rose, in their own research, are card-carrying reductionist biologists who  {114}  explain phenomena at the level of genes and molecules. Dawkins, in contrast, was trained as an ethologist and writes about the behavior of animals in their natural habitat. Wilson, for his part, is a pioneer of research in ecology and a passionate defender of the endangered field that molecular biologists dismissively refer to as “birdsy-woodsy” biology.

All else having failed, Lewontin, Rose, and Kamin finally pinned a damning quotation on Dawkins: “They [the genes] control us, body and mind.”³⁰ That does sound pretty deterministic. But what the man wrote was, “They created us, body and mind,” which is very different.³¹ Lewontin has used the doctored quotation in five different places.³²

Is there any charitable explanation of these “gross errors,” as Trivers called them? One possibility may be Dawkins's and Wilson's use of the expression “a gene for X” in discussing the evolution of social behavior like altruism, monogamy, and aggression. Lewontin, Rose, and Gould repeatedly pounce on this language, which refers, they think, to a gene that always causes the behavior and that is the only cause of the behavior. But Dawkins made it clear that the phrase refers to a gene that increases the probability of a behavior compared with alternative genes at that locus. And that probability is an average computed over the other genes that have accompanied it over evolutionary time, and over the environments that the organisms possessing the gene have lived in. This nonreductionist, nondeterminist use of the phrase “a gene for X” is routine among geneticists and evolutionary biologists because it is indispensable to what they do. Some behavior must be affected by some genes, or we could never explain why lions act differently from lambs, why hens sit on their eggs rather than eat them, why stags butt heads but gerbils don't, and so on. The point of evolutionary biology is to explain how these animals ended up with those genes, as opposed to genes with different effects. Now, a given gene may not have the same effect in all environments, nor the same effect in all genomes, but it has to have an average effect. That average is what natural selection selects (all things being equal), and that is all that the “for” means in “a gene for X.” It is hard to believe that Gould and Lewontin, who are evolutionary biologists, could literally have been confused by this usage, but if they were, it would explain twenty-five years of pointless attacks.

How low can one go? Ridiculing an opponent's sex life would seem to come right out of a bad satirical novel on academic life. But Lewontin, Rose, and Kamin bring up a suggestion by the sociologist Steven Goldberg that women are skilled at manipulating others’ emotions, and they comment, “What a touching picture of Goldberg's vulnerability to seduction is thus revealed!”³³ Later they mention a chapter in Donald Symons's groundbreaking book The Evolution of Human Sexuality which shows that in all societies, sex is typically conceived of as a female service or favor. “In reading sociobiology,” they comment, “one has the constant feeling of being a voyeur, peeping into  {115}  the autobiographical memoirs of its proponents.”³⁴ Rose was so pleased with this joke that he repeated it fourteen years later in his book Lifelines: Biology Beyond Determinism.³⁵

~

Any hope that these tactics are a thing of the past was dashed by events in the year 2000. Anthropologists have long been hostile to anyone who discusses human aggression in a biological context. In 1976 the American Anthropological Association nearly passed a motion censuring Sociobiology and banning two symposia on the topic, and in 1983 they did pass one decreeing that Derek Freeman's Margaret Mead and Samoa was “poorly written, unscientific, irresponsible, and misleading.”³⁶ But that was mild compared with what was to come.

In September 2000, the anthropologists Terence Turner and Leslie Sponsel sent the executives of the association a letter (which quickly proliferated throughout cyberspace) warning of a scandal for anthropology that was soon to be divulged in a book by the journalist Patrick Tierney.³⁷ The alleged perpetrators were the geneticist James Neel, a founder of the modern science of human genetics, and the anthropologist Napoleon Chagnon, famous for his thirty-year study of the Yanomamö people of the Amazon rainforest. Turner and Sponsel wrote:

This nightmarish story — a real anthropological heart of darkness beyond the imagining of even a Josef Conrad (though not, perhaps, a Josef Mengele) — will be seen (rightly in our view) by the public, as well as most anthropologists, as putting the whole discipline on trial. As another reader of the galleys put it, This book should shake anthropology to its very foundations. It should cause the field to understand how the corrupt and depraved protagonists could have spread their poison for so long while they were accorded great respect throughout the Western World and generations of undergraduates received their lies as the introductory substance of anthropology. This should never be allowed to happen again.

The accusations were truly shocking. Turner and Sponsel charged Neel and Chagnon with deliberately infecting the Yanomamö with measles (which is often fatal among indigenous peoples) and then withholding medical care in order to test Neel's “eugenically slanted genetic theories.” According to Turner and Sponsel's rendition of these theories, polygynous headmen in foraging societies were biologically fitter than coddled Westerners because they possessed “dominant genes” for “innate ability” that were selected when the headmen engaged in violent competition for wives. Neel believed, said Turner and Sponsel, that “democracy, with its free breeding for the masses and its sentimental  {116}  supports for the weak,” is a mistake. They reasoned, “The political implication of this fascistic eugenics is clearly that society should be reorganized into small breeding isolates in which genetically superior males could emerge into dominance, eliminating or subordinating the male losers in the competition for leadership and women, and amassing harems of brood females.”

The accusations against Chagnon were just as lurid. In his books and papers on the Yanomamö, Chagnon had documented their frequent warfare and raiding, and had presented data suggesting that men who had participated in a killing had more wives and offspring than those who had not.³⁸ (The finding is provocative because if that payoff was typical of the pre-state societies in which humans evolved, the strategic use of violence would have been selected over evolutionary time.) Turner and Sponsel accused him of fabricating his data, of causing the violence among the Yanomamö (by sending them into a frenzy over the pots and knives with which he paid his informants), and of staging lethal fights for documentary films. Chagnon's portrayal of the Yanomamö, they charged, had been used to justify an invasion of gold miners into their territory, abetted by Chagnon's collusion with “sinister” Venezuelan politicians. The Yanomamö have unquestionably been decimated by disease and by the depredations of the miners, so to lay these tragedies and crimes at Chagnon's feet is literally to accuse him of genocide. For good measure, Turner and Sponsel added that Tierney's book contained “passing references to Chagnon ... demanding that villagers bring him girls for sex.”

Headlines such as “Scientist ‘Killed Amazon Indians to Test Race Theory'” soon appeared around the world, followed by an excerpt of Tierney's book in The New Yorker and then the book itself, titled Darkness in El Dorado: How Scientists and Journalists Devastated the Amazon.³⁹ Under pressure from the publisher's libel lawyers, some of the more sensational accusations in the book had been excised, watered down, or put in the mouths of Venezuelan journalists or untraceable informants. But the substance of the charges remained.⁴⁰

Turner and Sponsel admitted that their charge against Neel “remains only an inference in the present state of our knowledge: there is no ‘smoking gun’ in the form of a written text or recorded speech by Neel.” That turned out to be an understatement. Within days, scholars with direct knowledge of the events — historians, epidemiologists, anthropologists, and filmmakers — demolished the charges point by point.⁴¹

Far from being a depraved eugenicist, James Neel (who died shortly before the accusations came out) was an honored and beloved scientist who had consistently attacked eugenics. Indeed, he is often credited with purging human genetics of old eugenic theories and thereby making it a respectable science. The cockamamie theory that Turner and Sponsel attributed to him was incoherent on the face of it and scientifically illiterate (for example, they confused a  {117}  “dominant gene” with a gene for dominance). In any case there is not the slightest evidence that Neel held any belief close to it. Records show that Neel and Chagnon were surprised by the measles epidemic already in progress and made heroic efforts to contain it. The vaccine they administered, which Tierney had charged was the source of the epidemic, has never caused contagious transmission of measles in the hundreds of millions of people all over the world who have received it, and in all probability the efforts of Neel and Chagnon saved hundreds of Yanomamö lives.⁴² Confronted with public statements from epidemiologists refuting his claims, Tierney lamely said, “Experts I spoke to then had very different opinions than the ones they are expressing in public now.”⁴³

Though no one can prove that Neel and Chagnon did not inadvertently introduce the disease in other places by their very presence, the odds are strongly against it. The Yanomamö, who are spread out over tens of thousands of square miles, had many more contacts with other Europeans than they did with Chagnon or Neel, because thousands of missionaries, traders, miners, and adventurers move through the area. Indeed, Chagnon himself had documented that a Catholic Salesian missionary was the likely source of an earlier outbreak. Together with Chagnon's criticism of the mission for providing the Yanomamö with shotguns, this earned him the missionaries’ undying enmity. Not coincidentally, most of Tierney's Yanomamö informants were associated with the mission.

The specific accusations against Chagnon crumbled as quickly as those against Neel. Chagnon, contrary to Tierney's charges, had not exaggerated Yanomamö violence or ignored the rest of their lifestyle; in fact, he had meticulously described their techniques for conflict resolution.⁴⁴ The suggestion that Chagnon introduced them to violence is simply incredible. Raiding and warfare among the Yanomamö have been described since the mid-1800s and were documented throughout the first half of the twentieth century, long before Chagnon set foot in the Amazon. (One revealing account was a first-person narrative called Yanodma: The Story of Helena Valero, a Girl Kidnapped by Amazonian Indians.)⁴⁵ And Chagnon's main empirical claims have met the gold standard of science: independent replication. In surveys of rates of death by warfare in pre-state societies, Chagnon's estimates for the Yanomamö fall well within the range, as we saw in the graph in Chapter 3.⁴⁶ Even his most controversial claim, that killers had more wives and offspring, has been replicated in other groups, though there is controversy over the interpretation. It is instructive to compare Tierney's summary of a book supposedly refuting Chagnon with the author's own words. Tierney reports:

Among the Jivaro, head-hunting was a ritual obligation of all males and a required male initiation for teenagers. There, too, most men died in  {117}  war. Among the Jivaro leaders, however, those who captured the most heads had the fewest wives, and those who had the most wives captured the fewest heads.⁴⁷

The author, the anthropologist Elsa Redmond, had actually written:

Yanomamö men who have killed tend to have more wives, which they have acquired either by abducting them from raiding villages, or by the usual marriage alliances in which they are considered more attractive as mates. The same is true of Jivaro war leaders, who might have four to six wives; as a matter of fact, a great war leader on the Upano River in the 1930s by the name of Tuki or Jose Grande had eleven wives. Distinguished warriors also have more offspring, due mainly to their greater marital success.⁴⁸

Turner and Sponsel had long been among Chagnon's most vehement critics (and, not coincidentally, major sources for Tierney's book, despite their professed shock at learning of its contents). They are open about their ideological agenda, which is to defend the doctrine of the Noble Savage. Sponsel wrote that he is committed to “the anthropology of peace” in order to promote a “more nonviolent and peaceful world,” which he believes is “latent in human nature.”⁴⁹ He is opposed to a “Darwinian emphasis on violence and competition” and recently pronounced that “nonviolence and peace were likely the norm throughout most of human prehistory and that intrahuman killing was probably rare.”⁵⁰ He even admits that much of his criticism of Chagnon comes from “an almost automatic reaction against any biological explanation of human behavior, the possibility of biological reductionism, and the associated political implications.”⁵¹

Also familiar from the radical science days is an irredentist leftism that considers even moderate and liberal positions reactionary. According to Tierney, Neel “was convinced that democracy, with its free breeding for the masses and its sentimental support for the weak, violated natural selection”⁵² and was thus “a eugenic mistake.” But in fact Neel was a political liberal who had protested the diversion of money from poor children to research on aging that he thought would benefit the affluent. He also advocated increasing investment in prenatal care, medical care for children and adolescents, and universal quality education.⁵³ As for Chagnon, Tierney calls him “a militant anti-Communist and free-market advocate.” His evidence? A quotation from Turner (!) stating that Chagnon is “a kind of right-wing character who has a paranoid attitude on people he considers lefty.” To explain how he came by these right-wing leanings, Tierney informs readers that Chagnon grew up in a part of rural Michigan “where differences were not welcomed, where  {119}  xenophobia, linked to anti-Communist feeling, ran high, and where Senator Joseph McCarthy enjoyed strong support.” Unaware of the irony, Tierney concludes that Chagnon is an “offspring” of McCarthy who had “received a full portion of [McCarthy's] spirit.” Chagnon, in fact, is a political moderate who had always voted for Democrats.⁵⁴

An autobiographical comment in Tierney's preface is revealing: “I gradually changed from being an observer to being an advocate.... traditional, objective journalism was no longer an option for me.”⁵⁵ Tierney believes that accounts of Yanomamö violence might be used by invaders to depict them as primitive savages who should be removed or assimilated for their own good. Defaming messengers like Chagnon is, in this view, an ennobling form of social action and a step for the cultural survival of indigenous peoples (despite the fact that Chagnon himself has repeatedly acted to protect the interests of the Yanomamö).

The decimation of native Americans by European disease and genocide over five hundred years is indeed one of the great crimes of history. But it is bizarre to blame the crime on a handful of contemporary scientists struggling to document their lifestyle before it vanishes forever under the pressures of assimilation. And it is a dangerous tactic. Surely indigenous peoples have a right to survive in their lands whether or not they — like all human societies — are prone to violence and warfare. Self-appointed “advocates” who link the survival of native peoples to the doctrine of the Noble Savage paint themselves into a terrible corner. When the facts show otherwise they either have inadvertently weakened the case for native rights or must engage in any means necessary to suppress the facts.

~

No one should be surprised that claims about human nature are controversial. Obviously any such claim should be scrutinized and any logical and empirical flaws pointed out, just as with any scientific hypothesis. But the criticism of the new sciences of human nature went well beyond ordinary scholarly debate. It turned into harassment, slurs, misrepresentation, doctored quotations, and, most recently, blood libel. I think there are two reasons for this illiberal behavior.

One is that in the twentieth century the Blank Slate became a sacred doctrine that, in the minds of its defenders, had to be either avowed with a perfect faith or renounced in every aspect. Only such black-and-white thinking could lead people to convert the idea that some aspects of behavior are innate into the idea that all aspects of behavior are innate, or convert the proposal that genetic traits influence human affairs into the idea that they determine human affairs. Only if it is theologically necessary for 100 percent of the differences in intelligence to be caused by the environment could anyone be incensed over the mathematical banality that as the proportion of variance due to nongenetic causes  {120}  goes down, the proportion due to genetic causes must go up. Only if the mind is required to be a scraped tablet could anyone be outraged by the claim that human nature makes us smile, rather than scowl, when we are pleased.

A second reason is that “radical” thinkers got trapped by their own moralizing. Once they staked themselves to the lazy argument that racism, sexism, war, and political inequality were factually incorrect because there is no such thing as human nature (as opposed to being morally despicable regardless of the details of human nature), every discovery about human nature was, by their own reasoning, tantamount to saying that those scourges were not so bad after all. That made it all the more pressing to discredit the heretics making the discoveries. If ordinary standards of scientific argumentation were not doing the trick, other tactics had to be brought in, because a greater good was at stake.

Chapter 7

The Holy Trinity

Behavioral science is not for sissies. Researchers may wake up to discover that they are despised public figures because of some area they have chosen to explore or some datum they have stumbled upon. Findings on certain topics — daycare, sexual behavior, childhood memories, the treatment of substance abuse — may bring on vilification, harassment, intervention by politicians, and physical assault.¹ Even a topic as innocuous as left-handedness turns out to be booby-trapped. In 1991 the psychologists Stanley Coren and Diane Halpern published statistics in a medical journal showing that lefties on average had more prenatal and perinatal complications, are victims of more accidents, and die younger than righties. They were soon showered with abuse — including the threat of a lawsuit, numerous death threats, and a ban on the topic in a scholarly journal — from enraged lefthanders and their advocates.²

Are the dirty tricks of the preceding chapter just another example of people taking offense at claims about behavior that make them uncomfortable? Or, as I have hinted, are they part of a systematic intellectual current: the attempt to safeguard the Blank Slate, the Noble Savage, and the Ghost in the Machine as a source of meaning and morality? The leading theoreticians of the radical science movement deny that they believe in a blank slate, and it is only fair that their positions be examined carefully. In addition, I will look at the attacks on the sciences of human nature that have come from their political opposites, the contemporary right.

~

Could the radical scientists really believe in the Blank Slate? The doctrine might seem plausible to some of the scholars who live in a world of disembodied ideas. But could hardheaded boffins who live in a mechanistic world of neurons and genes really think that the psyche soaks into the brain from the surrounding culture? They deny it in the abstract, but when it comes to specifics their position is plainly in the tradition of the tabula rasa social  {122}  science of the early twentieth century. Stephen Jay Gould, Richard Lewontin, and the other signatories of the “Against ‘Sociobiology'” manifesto wrote:

We are not denying that there are genetic components to human behavior. But we suspect that human biological universals are to be discovered more in the generalities of eating, excreting, and sleeping than in such specific and highly variable habits as warfare, sexual exploitation of women and the use of money as a medium of exchange.³

Note the tricky framing of the issue. The notion that money is a genetically coded universal is so ridiculous (and not, incidentally, something Wilson ever proposed) that any alternative has to be seen as more plausible than that. But if we take the alternative on its own terms, rather than as one prong in a false dichotomy, Gould and Lewontin seem to be saying that the genetic components of human behavior will be discovered primarily in the “generalities of eating, excreting, and sleeping.” The rest of the slate, presumably, is blank.

This debating tactic — first deny the Blank Slate, then make it look plausible by pitting it against a straw man — can be found elsewhere in the writings of the radical scientists. Gould, for instance, writes:

Thus, my criticism of Wilson does not invoke a non-biological “environmentalism”; it merely pits the concept of biological potentiality, with a brain capable of a full range of human behaviors and predisposed to none, against the idea of biological determinism, with specific genes for specific behavioral traits.⁴

The idea of “biological determinism” — that genes cause behavior with 100 percent certainty — and the idea that every behavioral trait has its own gene, are obviously daft (never mind that Wilson never embraced them). So Gould's dichotomy would seem to leave “biological potentiality” as the only reasonable choice. But what does that mean? The claim that the brain is “capable of a full range of human behaviors” is almost a tautology: how could the brain not be capable of a full range of human behaviors? And the claim that the brain is not predisposed to any human behavior is just a version of the Blank Slate. “Predisposed to none” literally means that all human behaviors have identical probabilities of occurring. So if any person anywhere on the planet has ever committed some act in some circumstance — abjuring food or sex, impaling himself with spikes, killing her child — then the brain has no predisposition to avoid that act as compared with the alternatives, such as enjoying food and sex, protecting one's body, or cherishing one's child.

Lewontin, Rose, and Kamin also deny that they are saying that humans are blank slates.⁵ But they grant only two concessions to human nature. The first  {123}  comes not from an appeal to evidence or logic but from their politics: “If [a blank slate] were the case, there could be no social evolution.” Their support for this “argument” consists of an appeal to the authority of Marx, whom they quote as saying, “The materialist doctrine that men are the products of circumstances and upbringing, and that, therefore, changed men are products of other circumstances and changed upbringing, forgets that it is men that change circumstances and that the educator himself needs educating.”⁶ Their own view is that “the only sensible thing to say about human nature is that it is ‘in’ that nature to construct its own history.”⁷ The implication is that any other statement about the psychological makeup of our species — about our capacity for language, our love of family, our sexual emotions, our typical fears, and so on — is not “sensible.”

Lewontin, Rose, and Kamin do make one concession to biology — not to the organization of the mind and brain but to the size of the body. “Were human beings only six inches tall there could be no human culture at all as we understand it,” they note, because a Lilliputian could not control fire, break rocks with a pick-axe, or carry a brain big enough to support language. It is their only acknowledgment of the possibility that human biology affects human social life.

Eight years later Lewontin reiterated this theory of what is innate in humans: “The most important fact about human genes is that they help to make us as big as we are and to have a central nervous system with as many connections as it has.”⁸ Once again, the rhetoric has to be unpacked with care. If we take the sentence literally, Lewontin is referring only to “the most important fact” about human genes. Then again, if we take it literally, the sentence is meaningless. How could one ever rank-order the thousands of effects of the genes, all necessary to our existence, and point to one or two at the top of the list? Is our stature more important than the fact that we have a heart, or lungs, or eyes? Is our synapse number more important than our sodium pumps, without which our neurons would fill up with positive ions and shut down? So taking the sentence literally is pointless. The only sensible reading, and the one that fits in the context, is that these are the only important facts about human genes for the human mind. The tens of thousands of genes that are expressed primarily or exclusively in the brain do nothing important but give it lots of connections; the pattern of connections and the organization of the brain (into structures like the hippocampus, amygdala, hypothalamus, and a cerebral cortex divided into areas) are random, or might as well be. The genes do not give the brain multiple memory systems, complicated visual and motor tracts, an ability to learn a language, or a repertoire of emotions (or else the genes do provide these faculties, but they are not “important”).

In an update of John Watson's claim that he could turn any infant into a “doctor, lawyer, artist, merchant-chief, and yes, even beggar-man and thief,  {124}  regardless of his talents, penchants, tendencies, abilities, vocations, and race of his ancestors,” Lewontin wrote a book whose jacket precis claims that “our genetic endowments confer a plasticity of psychic and physical development, so that in the course of our lives, from conception to death, each of us, irrespective of race, class, or sex, can develop virtually any identity that lies within the human ambit.”⁹ Watson admitted he was “going beyond my facts,” which was forgivable because at the time he wrote there were no facts. But the declaration on Lewontin's book that any individual can assume any identity (even granting the equivalence of races, sexes, and classes), in defiance of six decades of research in behavioral genetics, is an avowal of faith of uncommon purity. And in a passage that re-erects Durkheim's wall between the biological and the cultural, Lewontin concludes a 1992 book by writing that the genes “have been replaced by an entirely new level of causation, that of social interaction with its own laws and its own nature that can be understood and explored only through that unique form of experience, social action.”¹⁰

So while Gould, Lewontin, and Rose deny that they believe in a blank slate, their concessions to evolution and genetics — that they let us eat, sleep, urinate, defecate, grow bigger than a squirrel, and bring about social change — reveal them to be empiricists more extreme than Locke himself, who at least recognized the need for an innate faculty of “understanding.”

~

The Noble Savage, too, is a cherished doctrine among critics of the sciences of human nature. In Sociobiology, Wilson mentioned that tribal warfare was common in human prehistory. The against-sociobiologists declared that this had been “strongly rebutted both on the basis of historical and anthropological studies.” I looked up these “studies,” which were collected in Ashley Montagu's Man and Aggression. In fact they were just hostile reviews of books by the ethologist Konrad Lorenz, the playwright Robert Ardrey, and the novelist William Golding (author of Lord of the Flies).¹¹ Some of the criticisms were, to be sure, deserved: Ardrey and Lorenz believed in archaic theories such as that aggression was like the discharge of a hydraulic pressure and that evolution acted for the good of the species. But far stronger criticisms of Ardrey and Lorenz had been made by the sociobiologists themselves. (On the second page of The Selfish Gene, for example, Dawkins wrote, “The trouble with these books is that the authors got it totally and utterly wrong.”) In any case, the reviews contained virtually no data about tribal warfare. Nor did Montagu's summary essay, which simply rehashed attacks on the concept of “instinct” from decades of behaviorists. One of the only chapters with data “refuted” Lorenz's claims about warfare and raiding in the Ute Indians by saying they didn't do it any more than other native groups!

Twenty years later, Gould wrote that “Homo sapiens is not an evil or destructive species.” His new argument comes from what he calls the Great  {125}  Asymmetry. It is “an essential truth,” he writes, that “good and kind people outnumber all others by thousands to one.”¹² Moreover, “we perform 10,000 acts of small and unrecorded kindness for each surpassingly rare, but sadly balancing, moment of cruelty.”¹³ The statistics making up this “essential truth” are pulled out of the air and are certainly wrong: psychopaths, who are definitely not “good and kind people,” make up about three or four percent of the male population, not several hundredths of a percent.¹⁴ But even if we accept the figures, the argument assumes that for a species to count as “evil and destructive,” it would have to be evil and destructive all the time, like a deranged postal worker on a permanent rampage. It is precisely because one act can balance ten thousand kind ones that we call it “evil.” Also, does it make sense to judge our entire species, as if we were standing en masse at the pearly gates? The issue is not whether our species is “evil and destructive” but whether we house evil and destructive motives, together with the beneficent and constructive ones. If we do, one can try to understand what they are and how they work.

Gould has objected to any attempt to understand the motives for war in the context of human evolution, because “each case of genocide can be matched with numerous incidents of social beneficence; each murderous band can be paired with a pacific clan.”¹⁵ Once again a ratio has been conjured out of the blue; the data reviewed in Chapter 3 show that “pacific clans” either do not exist or are considerably outnumbered by the “murderous bands.”¹⁶ But for Gould, such facts are beside the point, because he finds it necessary to believe in the pacific clans on moral grounds. Only if humans lack any predisposition for good or evil or anything else, he suggests, do we have grounds for opposing genocide. Here is how he imagines the position of the evolutionary psychologists he disagrees with:

Perhaps the most popular of all explanations for our genocidal capacity cites evolutionary biology as an unfortunate source — and as an ultimate escape from full moral responsibility.... A group devoid of xenophobia and unschooled in murder might invariably succumb to others replete with genes to encode a propensity for such categorization and destruction. Chimpanzees, our closest relatives, will band together and systematically kill the members of adjacent groups. Perhaps we are programmed to act in such a manner as well. These grisly propensities once promoted the survival of groups armed with nothing more destructive than teeth and stones. In a world of nuclear bombs, such unchanged (and perhaps unchangeable) inheritances may now spell our undoing (or at least propagate our tragedies) — but we cannot be blamed for these moral failings. Our accursed genes have made us creatures of the night.¹⁷  {126} 

In this passage Gould presents a more-or-less reasonable summary of why scientists might think that human violence can be illuminated by evolution. But then he casually slips in some outrageous non sequiturs (“an ultimate escape from full moral responsibility,” “we cannot be blamed”), as if the scientists had no choice but to believe those, too. He concludes his essay:

In 1525, thousands of German peasants were slaughtered..., and Michelangelo worked on the Medici Chapel.... Both sides of this dichotomy represent our common, evolved humanity. Which, ultimately, shall we choose? As to the potential path of genocide and destruction, let us take this stand. It need not be. We can do otherwise.¹⁸

The implication is that anyone who believes that the causes of genocide might be illuminated by an understanding of the evolved makeup of human beings is in fact taking a stand in favor of genocide!

~

What about the third member of the trinity, the Ghost in the Machine? The radical scientists are thoroughgoing materialists and could hardly believe in an immaterial soul. But they are equally uncomfortable with any clearly stated alternative, because it would cramp their political belief that we can collectively implement any social arrangement we choose. To update Ryle's description of Descartes's dilemma: as men of scientific acumen they cannot but endorse the claims of biology, yet as political men they cannot accept the discouraging rider to those claims, namely that human nature differs only in degree of complexity from clockwork.

Ordinarily it is not cricket to bring up the political beliefs of scholars in discussing their scholarly arguments, but it is Lewontin and Rose who insist that their scientific beliefs are inseparable from their political ones. Lewontin wrote a book with the biologist Richard Levins called The Dialectical Biologist, which they dedicated to Friedrich Engels (“who got it wrong a lot of the time but got it right where it counted”). In it they wrote, “As working scientists in the field of evolutionary genetics and ecology, we have been attempting with some success to guide our research by a conscious application of Marxist philosophy.”¹⁹ In Not in Our Genes, Lewontin, Rose, and Kamin declared that they “share a commitment to the prospect of a more socially just — a socialist — society” and see their “critical science as an integral part of the struggle to create that society.”²⁰ At one point they frame their disagreement with “reductionism” as follows:

Against this economic reduction as the explanatory principle underlying all human behavior, we could counterpose the ... revolutionary practitioners and theorists like Mao Tse-tung on the power of human consciousness in both interpreting and changing the world, a power  {127}  based on an understanding of the essential dialectical unity of the biological and the social, not as two distinct spheres, or separable components of action, but as ontologically coterminous.²¹

Lewontin and Rose's commitment to the “dialectical” approach of Marx, Engels, and Mao explains why they deny human nature and also deny that they deny it. The very idea of a durable human nature that can be discussed separately from its ever-changing interaction with the environment is, in their view, a dull-witted mistake. The mistake lies not just in ignoring interactions with the environment — Lewontin and Rose already knocked over the straw men who do that. The deeper mistake, as they see it, lies in trying to analyze behavior as an interaction between human nature and the human environment (including society) in the first place.²² The very act of separating them in one's mind, even for the purpose of figuring out how the two interact, “supposes the alienation of the organism and the environment.” That contradicts the principles of dialectical understanding, which says that the two are “ontologically coterminous” — not just in the trivial sense that no organism lives in a vacuum, but in the sense that they are inseparable in every aspect of their being.

Since the dialectic between organism and environment constantly changes over historical time, with neither one directly causing the other, organisms can alter that dialectic. Thus Rose repeatedly counters the “determinists” with the declaration “We have the ability to construct our own futures, albeit not in circumstances of our own choosing”²³ — presumably echoing Marx's statement that “men make their own history, but they do not make it lust as they please; they make it under circumstances directly encountered, given and transmitted from the past.” But Rose never explains who the “we” is, if not highly structured neural circuits, which must get that structure in part from genes and evolution. We can call this doctrine the Pronoun in the Machine.

Gould is not a doctrinarian like Rose and Lewontin, but he too uses the first-person plural pronoun as if it somehow disproved the relevance of genes and evolution to human affairs: “Which ... shall we choose?... Let us take this stand.... We can do otherwise.” And he too cites Marx's “wonderful aphorism” about making our own history and believes that Marx vindicated the concept of free will:

Marx himself had a much more subtle view than most of his contemporaries of the differences between human and natural history. He understood that the evolution of consciousness, and the consequent development of social and economic organization, introduced elements of difference and volition that we usually label as “free will.”²⁴  {128} 

Subtle indeed is the argument that explains free will in terms of its synonym “volition” (with or without “elements of difference,” whatever that means) and attributes it to the equally mysterious “evolution of consciousness.” Basically, Rose and Gould are struggling to make sense of the dichotomy they invented between a naturally selected, genetically organized brain on one side and a desire for peace, justice, and equality on the other. In Part III we will see that the dichotomy is a false one.

The doctrine of the Pronoun in the Machine is not a casual oversight in the radical scientists’ world view. It is consistent with their desire for radical political change and their hostility to “bourgeois” democracy. (Lewontin repeatedly uses “bourgeois” as an epithet.) If the “we” is truly unfettered by biology, then once “we” see the light we can carry out the vision of radical change that we deem correct. But if the “we” is an imperfect product of evolution — limited in knowledge and wisdom, tempted by status and power, and blinded by self-deception and delusions of moral superiority — then “we” had better think twice before constructing all that history. As the chapter on politics will explain, constitutional democracy is based on a jaundiced theory of human nature in which “we” are eternally vulnerable to arrogance and corruption. The checks and balances of democratic institutions were explicitly designed to stalemate the often dangerous ambitions of imperfect humans.

~

The Ghost in the Machine, of course, is far dearer to the political right than to the political left. In his book The New Know-Nothings: The Political Foes of the Scientific Study of Human Nature, the psychologist Morton Hunt has shown that the foes include people on the left, people on the right, and a motley collection of single-issue fanatics in between.²⁵ So far I have discussed the far-left outrage because it has been deployed in the battlefield of ideas in the universities and the mainstream press. Those on the far right have also been outraged, though until recently they have aimed at different targets and have fought in different arenas.

The longest-standing right-wing opposition to the sciences of human nature comes from the religious sectors of the coalition, especially Christian fundamentalism. Anyone who doesn't believe in evolution is certainly not going to believe in the evolution of the mind, and anyone who believes in an immaterial soul is certainly not going to believe that thought and feeling consist of information processing in the tissues of the brain.

The religious opposition to evolution is fueled by several moral fears. Most obviously, the fact of evolution challenges the literal truth of the creation story in the Bible and thus the authority that religion draws from it. As one creationist minister put it, “If the Bible gets it wrong in biology, then why should I trust the Bible when it talks about morality and salvation?”²⁶

But the opposition to evolution goes beyond a desire to defend biblical  {129}  literalism. Modern religious people may not believe in the literal truth of every miracle narrated in the Bible, but they do believe that humans were designed in God's image and placed on earth for a larger purpose — namely, to live a moral life by following God's commandments. If humans are accidental products of the mutation and selection of chemical replicators, they worry, morality would have no foundation and we would be left mindlessly obeying biological urges. One creationist, testifying to this danger in front of the U.S. House Judiciary Committee, cited the lyrics of a rock song: “You and me baby ain't nothin’ but mammals / So let's do it like they do it on the Discovery Channel.”²⁷ After the 1999 lethal rampage by two teenagers at Columbine High School in Colorado, Tom Delay, the Republican Majority Whip in the House of Representatives, said that such violence is inevitable as long as “our school systems teach children that they are nothing but glorified apes, evolutionized out of some primordial soup of mud.”²⁸

The most damaging effect of the right-wing opposition to evolution is the corruption of American science education by activists in the creationist movement. Until a Supreme Court decision in 1968, states were allowed to ban the teaching of evolution outright. Since then, creationists have tried to hobble it in ways that they hope will pass constitutional muster. These include removing evolution from science proficiency standards, demanding disclaimers that it is “only a theory,” watering down the curriculum, and opposing textbooks with good coverage of evolution or imposing ones with coverage of creationism. In recent years the National Center for Science Education has learned of new instances of these tactics at a rate of about one a week, coming from forty states.²⁹

The religious right is discomfited not just by evolution but by neuro-science. By exorcising the ghost in the machine, brain science is undermining two moral doctrines that depend on it. One is that every person has a soul, which finds value, exercises free will, and is responsible for its choices. If behavior is controlled instead by circuits in the brain that follow the laws of chemistry, choice and value would be myths and the possibility of moral responsibility would evaporate. As the creationist advocate John West put it, “If human beings (and their beliefs) really are the mindless products of their material existence, then everything that gives meaning to human life — religion, morality, beauty — is revealed to be without objective basis.”³⁰

The other moral doctrine (which is found in some, but not all, Christian denominations) is that the soul enters the body at conception and leaves it at death, thereby defining who is a person with a right to life. The doctrine makes abortion, euthanasia, and the harvesting of stem cells from blastocysts equivalent to murder. It makes humans fundamentally different from animals. And it makes human cloning a violation of the divine order. All this would seem to be threatened by neuroscientists, who say that the self or the soul inheres in neural activity that develops gradually in the brain of an embryo, that can be  {130}  seen in the brains of animals, and that can break down piecemeal with aging and disease. (We will return to this issue in Chapter 13.)

But the right-wing opposition to the sciences of human nature can no longer be associated only with Bible-thumpers and televangelists. Today evolution is being challenged by some of the most cerebral theorists in the formerly secular neoconservative movement. They are embracing a hypothesis called Intelligent Design, originated by the biochemist Michael Behe.³¹ The molecular machinery of cells cannot function in a simpler form, Behe argues, and therefore it could not have evolved piecemeal by natural selection. Instead it must have been conceived as a working invention by an intelligent designer. The designer could, in theory, have been an advanced alien from outer space, but everyone knows that the subtext of the theory is that it must have been God.

Biologists reject Behe's argument for a number of reasons.³² His specific claims about the “irreducible complexity” of biochemistry are unproven or just wrong. He takes every phenomenon whose evolutionary history has not yet been figured out and chalks it up to design by default. When it comes to the intelligent designer, Behe suddenly jettisons all scientific scruples and does not question where the designer came from or how the designer works. And he ignores the overwhelming evidence that the process of evolution, far from being intelligent and purposeful, is wasteful and cruel.

Nonetheless, Intelligent Design has been embraced by leading neoconservatives, including Irving Kristol, Robert Bork, Roger Kimball, and Gertrude Himmelfarb. Other conservative intellectuals have also sympathized with creationism for moral reasons, such as the law professor Philip Johnson, the writer William F. Buckley, the columnist Tom Bethell, and, disconcertingly, the bioethicist Leon Kass — chair of George W. Bush's new Council on Bioethics and thus a shaper of the nation's policies on biology and medicine.³³ A story entitled “The Deniable Darwin” appeared, astonishingly, on the cover of Commentary, which means that a magazine that was once a leading forum for secular Jewish intellectuals is now more skeptical of evolution than is the Pope!³⁴

It is not clear whether these worldly thinkers are really convinced that Darwinism is false or whether they think it is important for other people to believe it is false. In a scene from Inherit the Wind, the play about the Scopes Monkey Trial, the prosecutor and defense attorney (based on William Jennings Bryan and Clarence Darrow) are relaxing together after a day in court. The prosecutor says of the Tennessee locals:

They're simple people, Henry; poor people. They work hard and they need to believe in something, something beautiful. Why do you want to take it away from them? It's all they have.

That is not far from the attitude of the neocons. Kristol has written:  {131} 

If there is one indisputable fact about the human condition it is that no community can survive if it is persuaded — or even if it suspects — that its members are leading meaningless lives in a meaningless universe.³⁵

He spells out the moral corollary:

There are different kinds of truths for different kinds of people. There are truths appropriate for children; truths that are appropriate for students; truths that are appropriate for educated adults; and truths that are appropriate for highly educated adults, and the notion that there should be one set of truths available to everyone is a modern democratic fallacy. It doesn't work.³⁶

As the science writer Ronald Bailey observes, “Ironically, today many modern conservatives fervently agree with Karl Marx that religion is ‘the opium of the people'; they add a heartfelt, ‘Thank God!’ “³⁷

Many conservative intellectuals join fundamentalist Christians in deploring neuroscience and evolutionary psychology, which they see as explaining away the soul, eternal values, and free choice. Kass writes:

With science, the leading wing of modern rationalism, has come the progressive demystification of the world. Falling in love, should it still occur, is for the modern temper to be explained not by demonic possession (Eros) born of the soul-smiting sight of the beautiful (Aphrodite) but by a rise in the concentration of some still-to-be-identified polypeptide hormone in the hypothalamus. The power of religious sensibilities and understandings fades too. Even if it is true that the great majority of Americans still profess a belief in God, He is for few of us a God before whom one trembles in fear of judgment.³⁸

Similarly, the journalist Andrew Ferguson warns his readers that evolutionary psychology “is sure to give you the creeps,” because “whether behavior is moral, whether it signifies virtue, is a judgment that the new science, and materialism in general, cannot make.”³⁹ The new sciences, he writes, claim that people are nothing but “meat puppets,” a frightening shift from the traditional Judeo-Christian view in which “human beings [are] persons from the start, endowed with a soul, created by God, and infinitely precious.”⁴⁰

Even the left-baiting author Tom Wolfe, who admires neuroscience and evolutionary psychology, worries about their moral implications. In his essay “Sorry, but Your Soul Just Died,” he writes that when science has finally killed the soul (“that last refuge of values”), “the lurid carnival that will ensue may make [Nietzsche's] phrase ‘the total eclipse of all values’ seem tame”:  {132} 

Meanwhile, the notion of a self — a self who exercises self-discipline, postpones gratification, curbs the sexual appetite, stops short of aggression and criminal behavior — a self who can become more intelligent and lift itself to the very peaks of life by its own bootstraps through study, practice, perseverance, and refusal to give up in the face of great odds — this old-fashioned notion (what's a bootstrap, for God's sake?) of success through enterprise and true grit is already slipping away, slipping away... slipping away...⁴¹

“Where does that leave self-control?” he asks. “Where, indeed, if people believe this ghostly self does not even exist, and brain imaging proves it, once and for all?”⁴²

An irony in the modern denial of human nature is that partisans at opposite extremes of the political spectrum, who ordinarily can't stand the sight of each other, find themselves strange bedfellows. Recall how the signatories of “Against ‘Sociobiology'” wrote that theories like Wilson's “provided an important basis for ... the eugenics policies which led to the establishment of gas chambers in Nazi Germany.” In May 2001 the Education Committee of the Louisiana House of Representatives resolved that “Adolf Hitler and others have exploited the racist views of Darwin and those he influenced ... to justify the annihilation of millions of purportedly racially inferior individuals.”⁴³ The sponsor of the resolution (which was eventually defeated) cited in its defense a passage by Gould, which is not the first time that he has been cited approvingly in creationist propaganda.⁴⁴ Though Gould has been a tireless opponent of creationism, he has been an equally tireless opponent of the idea that evolution can explain mind and morality, and that is the implication of Darwinism that creationists fear most.

The left and the right also agree that the new sciences of human nature threaten the concept of moral responsibility. When Wilson suggested that in humans, as in many other mammals, males have a greater desire for multiple sexual partners than do females, Rose accused him of really saying:

Don't blame your mates for sleeping around, ladies, it's not their fault they are genetically programmed.⁴⁵

Compare Tom Wolfe, tongue only partly in cheek:

The male of the human species is genetically hardwired to be polygamous, i.e., unfaithful to his legal mate. Any magazine-reading male gets the picture soon enough. (Three million years of evolution made me do it!)⁴⁶  {133} 

On one wing we have Gould asking the rhetorical question:

Why do we want to fob off responsibility for our violence and sexism upon our genes?⁴⁷

And on the other wing we find Ferguson raising the same point:

The “scientific belief” would ... appear to be corrosive of any notion of free will, personal responsibility, or universal morality.⁴⁸

For Rose and Gould the ghost in the machine is a “we” that can construct history and change the world at will. For Kass, Wolfe, and Ferguson it is a “soul” that makes moral judgments according to religious precepts. But all of them see genetics, neuroscience, and evolution as threats to this irreducible locus of free choice.

~

Where does this leave intellectual life today? The hostility to the sciences of human nature from the religious right is likely to increase, but the influence of the right will be felt more in direct appeals to politicians than from changes in the intellectual climate. Any inroads of the religious right into mainstream intellectual life will be limited by their opposition to the theory of evolution itself. Whether it is known as creationism or by the euphemism Intelligent Design, a denial of the theory of natural selection will founder under the weight of the mass of evidence that the theory is correct. How much additional damage the denial will do to science education and biomedical research before it sinks is unknown.

The hostility from the radical left, on the other hand, has left a substantial mark on modern intellectual life, because the so-called radical scientists are now the establishment. I have met many social and cognitive scientists who proudly say they have learned all their biology from Gould and Lewontin.⁴⁹ Many intellectuals defer to Lewontin as the infallible pontiff of evolution and genetics, and many philosophers of biology spent time as his apprentice. A sneering review by Rose of every new book on human evolution or genetics has become a fixture of British journalism. As for Gould, Isaac Asimov probably did not intend the irony when he wrote in a book blurb that “Gould can do no wrong,” but that is precisely the attitude of many journalists and social scientists. A recent article in New York magazine on the journalist Robert Wright called him a “stalker” and a “young punk” with “penis envy” because he had the temerity to criticize Gould on his logic and facts.⁵⁰

In part the respect awarded to the radical scientists has been earned. Quite aside from their scientific accomplishments, Lewontin is an incisive analyst on  {134}  many scientific and social issues, Gould has written hundreds of superb essays on natural history, and Rose wrote a fine book on the neuroscience of memory. But they have also positioned themselves shrewdly on the intellectual landscape. As the biologist John Alcock explains, “Stephen Jay Gould abhors violence, he speaks out against sexism, he despises Nazis, he finds genocide horrific, he is unfailingly on the side of the angels. Who can argue with such a person?”⁵¹ This immunity from argument allowed the radical scientists’ unfair attacks on others to become part of the conventional wisdom.

Many writers today casually equate behavioral genetics with eugenics, as if studying the genetic correlates of behavior were the same as coercing people in their decisions about having children. Many equate evolutionary psychology with Social Darwinism, as if studying our evolutionary roots were the same as justifying the station of the poor. The confusions do not come only from the scientifically illiterate but may be found in prestigious publications such as Scientific American and Science.⁵² After Wilson argued in Consilience that divisions between fields of human knowledge were becoming obsolete, the historian Tzvetan Todorov wrote sarcastically, “I have a proposal for Wilson's next book ... [an] analysis of Social Darwinism, the doctrine that was adopted by Hitler, and of the ways it differs from sociobiology.”⁵³ When the Human Genome Project was completed in 2001, its leaders made a ritual denunciation of “genetic determinism,” the belief — held by no one — that “all characteristics of the person are ‘hard-wired’ into our genome.”⁵⁴

Even many scientists are perfectly content with the radicals’ social constructionism, not so much because they agree with it but because they are preoccupied in their labs and need picketers outside their window like they need another hole in the head. As the anthropologist John Tooby and the psychologist Leda Cosmides note, the dogma that biology is intrinsically disconnected from the human social order offers scientists “safe conduct across the politicized minefield of modern academic life.”⁵⁵ As we shall see, even today people who challenge the Blank Slate or the Noble Savage are still sometimes silenced by demonstrators or denounced as Nazis. Even when such attacks are sporadic, they create an atmosphere of intimidation that distorts scholarship far and wide.

But the intellectual climate is showing signs of change. Ideas about human nature, while still anathema to some academics and pundits, are beginning to get a hearing. Scientists, artists, scholars in the humanities, legal theorists, and thoughtful laypeople have expressed a thirst for the new insights about the mind that have been coming out of the biological and cognitive sciences. And the radical science movement, for all its rhetorical success, has turned out to be an empirical wasteland. Twenty-five years of data have not been kind to its predictions. Chimpanzees are not peaceful vegetarians, as Montagu claimed, nor is the heritability of intelligence indistinguishable from zero, IQ a  {135}  “reification” unrelated to the brain, personality and social behavior without any genetic basis, gender differences a product only of “psychocultural expectations,” or the number of murderous clans equal to the number of pacific bands.⁵⁶ Today the idea of guiding scientific research by “a conscious application of Marxist philosophy” is just embarrassing, and as the evolutionary psychologist Martin Daly pointed out, “Sufficient research to fill a first issue of Dialectical Biology has yet to materialize.”⁵⁷

In contrast, sociobiology did not, as Sahlins had predicted, turn out to be a passing fad. The title of Alcock's 2001 book The Triumph of Sociobiology says it all: in the study of animal behavior, no one even talks about “sociobiology” or “selfish genes” anymore, because the ideas are part and parcel of the science.⁵⁸ In the study of humans, there are major spheres of human experience — beauty, motherhood, kinship, morality, cooperation, sexuality, violence — in which evolutionary psychology provides the only coherent theory and has spawned vibrant new areas of empirical research.⁵⁹ Behavioral genetics has revivified the study of personality and will only expand with the application of knowledge from the Human Genome Project.⁶⁰ Cognitive neuroscience will not shrink from applying its new tools to every aspect of mind and behavior, including the emotionally and politically charged ones.

The question is not whether human nature will increasingly be explained by the sciences of mind, brain, genes, and evolution, but what we are going to do with the knowledge. What in fact are the implications for our ideals of equality, progress, responsibility, and the worth of the person? The opponents of the sciences of human nature from the left and the right are correct about one thing: these are vital questions. But that is all the more reason that they be confronted not with fear and loathing but with reason. That is the goal of the next part of the book.

HUMAN NATURE WITH A HUMAN FACE

W

hen Galileo attracted the unwanted attention of the Inquisition in 1633, more was at stake than issues in astronomy. By stating that the Earth revolved around the sun rather than vice versa, Galileo was contradicting the literal truth of the Bible, such as the passage in which Joshua issued the successful command “Sun, stand thou still.” Worse, he was challenging a theory of the moral order of the universe.

According to the theory, developed in medieval times, the sphere of the moon divided the universe into an unchanging perfection in the heavens above and a corrupt degeneration in the Earth below (hence Samuel Johnson's disclaimer that he could not “change sublunary nature”). Surrounding the moon were spheres for the inner planets, the sun, the outer planets, and the fixed stars, each cranked by a higher angel. And surrounding them all were the heavens, home to God. Contained within the sphere of the moon, and thus a little lower than the angels, were human souls, and then, in descending order, human bodies, animals (in the order beasts, birds, fish, insects), then plants, minerals, the inanimate elements, nine layers of devils, and finally, at the center of the Earth, Lucifer in hell. The universe was thus arranged in a hierarchy, a Great Chain of Being.

The Great Chain was thick with moral implications. Our home, it was thought, lay at the center of the universe, reflecting the importance of our existence and behavior. People lived their lives in their proper station (king, duke, or peasant), and after death their souls rose to a higher place or sank to a lower one. Everyone had to be mindful that the human abode was a humble place in the scheme of things and that they must look up to catch a glimpse of heavenly perfection. And in a world that seemed always to teeter on the brink of famine and barbarism, the Great Chain offered the comfort of knowing that the nature of things was orderly. If the planets wandered from their spheres, chaos would break out, because everything was connected in the cosmic order.  {138} 

As Alexander Pope wrote, “From Nature's chain whatever link you strike, / Tenth, or ten thousandth, breaks the chain alike.”¹

None of this escaped Galileo as he was pounding away at his link. He knew that he could not simply argue on empirical grounds that the division between a corrupt Earth and the unchanging heavens was falsified by sunspots, novas, and moons drifting across Jupiter. He also argued that the moral trappings of the geocentric theory were as dubious as its empirical claims, so if the theory turned out to be false, no one would be the worse. Here is Galileo's alter ego in Dialogue Concerning the Two Chief World Systems, wondering what is so great about being invariant and inalterable:

For my part I consider the earth very noble and admirable precisely because of the diverse alterations, changes, generations, etc. that occur in it incessantly. If, not being subject to any changes, it were a vast desert of sand or mountain of jasper, or if at the time of the flood the waters which covered it had frozen, and it had remained an enormous globe of ice where nothing was ever born or ever altered or changed, I should deem it a useless lump in the universe, devoid of activity and, in a word, superfluous and essentially nonexistent. This is exactly the difference between a living animal and a dead one; and I say the same of the moon, of Jupiter, and of all other world globes.

... Those who so greatly exalt incorruptibility, inalterability, et cetera, are reduced to talking this way, I believe, by their great desire to go on living, and by the terror they have of death. They do not reflect that if men were immortal, they themselves would never have come into the world. Such men really deserve to encounter a Medusa's head which would transmute them into statues of jasper or diamond, and thus make them more perfect than they are.²

Today we see things Galileo's way. It's hard for us to imagine why the three-dimensional arrangement of rock and gas in space should have anything to do with right and wrong or with the meaning and purpose of our lives. The moral sensibilities of Galileo s time eventually adjusted to the astronomical facts, not just because they had to give a nod to reality but because the very idea that morality has something to do with a Great Chain of Being was daffy to begin with.

We are now living, I think, through a similar transition. The Blank Slate is today's Great Chain of Being: a doctrine that is widely embraced as a rationale for meaning and morality and that is under assault from the sciences of the day. As in the century following Galileo, our moral sensibilities will adjust to the biological facts, not only because facts are facts but because the moral credentials of the Blank Slate are just as spurious.  {139} 

This part of the book will show why a renewed conception of meaning and morality will survive the demise of the Blank Slate. I am not, to say the least, proposing a novel philosophy of life like the spiritual leader of some new cult. The arguments I will lay out have been around for centuries and have been advanced by some of history's greatest thinkers. My goal is to put them down in one place and connect them to the apparent moral challenges from the sciences of human nature, to serve as a reminder of why the sciences will not lead to a Nietzschean total eclipse of all values.

The anxiety about human nature can be boiled down to four fears:

• If people are innately different, oppression and discrimination would be justified.

• If people are innately immoral, hopes to improve the human condition would be futile.

• If people are products of biology, free will would be a myth and we could no longer hold people responsible for their actions.

• If people are products of biology, life would have no higher meaning and purpose.

Each will get a chapter. I will first explain the basis of the fear: which claims about human nature are at stake, and why they are thought to have treacherous implications. I will then show that in each case the logic is faulty; the implications simply do not follow. But I will go farther than that. It's not just that claims about human nature are less dangerous than many people think. It's that the denial of human nature can be more dangerous than people think. This makes it imperative to examine claims about human nature objectively, without putting a moral thumb on either side of the scale, and to figure out how we can live with the claims should they turn out to be true.

Chapter 8

The Fear of Inequality

The greatest moral appeal of the doctrine of the Blank Slate comes from a simple mathematical fact: zero equals zero. This allows the Blank Slate to serve as a guarantor of political equality. Blank is blank, so if we are all blank slates, the reasoning goes, we must all be equal. But if the slate of a newborn is not blank, different babies could have different things inscribed on their slates. Individuals, sexes, classes, and races might differ innately in their talents, abilities, interests, and inclinations. And that, it is thought, could lead to three evils.

The first is prejudice: if groups of people are biologically different, it could be rational to discriminate against the members of some of the groups. The second is Social Darwinism: if differences among groups in their station in life — their income, status, and crime rate, for example — come from their innate constitutions, the differences cannot be blamed on discrimination, and that makes it easy to blame the victim and tolerate inequality. The third is eugenics: if people differ biologically in ways that other people value or dislike, it would invite them to try to improve society by intervening biologically — by encouraging or discouraging people's decisions to have children, by taking that decision out of their hands, or by killing them outright. The Nazis carried out the “final solution” because they thought Jews and other ethnic groups were biologically inferior. The fear of the terrible consequences that might arise from a discovery of innate differences has thus led many intellectuals to insist that such differences do not exist — or even that human nature does not exist, because if it did, innate differences would be possible.

I hope that once this line of reasoning is laid out, it will immediately set off alarm bells. We should not concede that any foreseeable discovery about humans could have such horrible implications. The problem is not with the possibility that people might differ from one another, which is a factual question that could turn out one way or the other. The problem is with the line of reasoning that says that if people do turn out to be different, then discrimination, oppression, or genocide would be OK after all. Fundamental values (such as  {142}  equality and human rights) should not be held hostage to some factual conjecture about blank slates that might be refuted tomorrow. In this chapter we will see how these values might be put on a more secure foundation.

~

What kinds of differences are there to worry about? The chapters on gender and children will review the current evidence on differences between sexes and individuals, together with their implications and non-implications. The goal of this part of the chapter is more general: to lay out the kinds of differences that research could turn up over the long term, based on our understanding of human evolution and genetics, and to lay out the moral issues they raise.

This book is primarily about human nature — an endowment of cognitive and emotional faculties that is universal to healthy members of Homo sapiens. Samuel Johnson wrote, “We are all prompted by the same motives, all deceived by the same fallacies, all animated by hope, obstructed by danger, entangled by desire, and seduced by pleasure.”¹ The abundant evidence that we share a human nature does not mean that the differences among individuals, races, or sexes are also in our nature. Confucius could have been right when he wrote, “Men's natures are alike; it is their habits that carry them far apart.”²

Modern biology tells us that the forces that make people alike are not the same as the forces that make people different.³ (Indeed, they tend to be studied by different scientists: the similarities by evolutionary psychologists, the differences by behavioral geneticists.) Natural selection works to homogenize a species into a standard overall design by concentrating the effective genes — the ones that build well-functioning organs — and winnowing out the ineffective ones. When it comes to an explanation of what makes us tick, we are thus birds of a feather. Just as we all have the same physical organs (two eyes, a liver, a four-chambered heart), we have the same mental organs. This is most obvious in the case of language, where every neurologically intact child is equipped to acquire any human language, but it is true of other parts of the mind as well. Discarding the Blank Slate has thrown far more light on the psychological unity of humankind than on any differences.⁴

We are all pretty much alike, but we are not, of course, clones. Except in the case of identical twins, each person is genetically unique. That is because random mutations infiltrate the genome and take time to be eliminated, and they are shuffled together in new combinations when individuals sexually reproduce. Natural selection tends to preserve some degree of genetic heterogeneity at the microscopic level in the form of small, random variations among proteins. That variation twiddles the combinations of an organism's molecular locks and keeps its descendants one step ahead of the microscopic germs that are constantly evolving to crack those locks.

All species harbor genetic variability, but Homo sapiens is among the less variable ones. Geneticists call us a “small” species, which sounds like a bad joke  {143}  given that we have infested the planet like roaches. What they mean is that the amount of genetic variation found among humans is what a biologist would expect in a species with a small number of members.⁵ There are more genetic differences among chimpanzees, for instance, than there are among humans, even though we dwarf them in number. The reason is that our ancestors passed through a population bottleneck fairly recently in our evolutionary history (less than a hundred thousand years ago) and dwindled to a small number of individuals with a correspondingly small amount of genetic variation. The species survived and rebounded, and then underwent a population explosion after the invention of agriculture about ten thousand years ago. That explosion bred many copies of the genes that were around when we were sparse in number; there has not been much time to accumulate many new versions of the genes.

At various points after the bottleneck, differences between races emerged. But the differences in skin and hair that are so obvious when we look at people of other races are really a trick played on our intuitions. Racial differences are largely adaptations to climate. Skin pigment was a sunscreen for the tropics, eyelid folds were goggles for the tundra. The parts of the body that face the elements are also the parts that face the eyes of other people, which fools them into thinking that racial differences run deeper than they really do.⁶ Working in opposition to the adaptation to local climates, which makes groups different on the skin, is an evolutionary force that makes neighboring groups similar inside. Rare genes can offer immunity to endemic diseases, so they get sucked into one group from a neighboring group like ink on a blotter, even if members of one group mate with members of the other infrequently.⁷ That is why Jews, for example, tend to be genetically similar to their non-Jewish neighbors all over the world, even though until recently they tended to marry other Jews. As little as one conversion, affair, or rape involving a gentile in every generation can be enough to blur genetic boundaries over time.⁸

Taking all these processes into account, we get the following picture. People are qualitatively the same but may differ quantitatively. The quantitative differences are small in biological terms, and they are found to a far greater extent among the individual members of an ethnic group or race than between ethnic groups or races. These are reassuring findings. Any racist ideology that holds that the members of an ethnic group are all alike, or that one ethnic group differs fundamentally from another, is based on false assumptions about our biology.

But biology does not let us off the hook entirely. Individuals are not genetically identical, and it is unlikely that the differences affect every part of the body except the brain. And though genetic differences between races and ethnic groups are much smaller than those among individuals, they are not nonexistent (as we see in their ability to give rise to physical differences and to  {144}  different susceptibilities to genetic diseases such as Tay-Sachs and sickle cell anemia). Nowadays it is popular to say that races do not exist but are purely social constructions. Though that is certainly true of bureaucratic pigeonholes such as “colored,” “Hispanic,” “Asian/Pacific Islander,” and the one-drop rule for being “black,” it is an overstatement when it comes to human differences in general. The biological anthropologist Vincent Sarich points out that a race is just a very large and partly inbred family. Some racial distinctions thus may have a degree of biological reality, even though they are not exact boundaries between fixed categories. Humans, having recently evolved from a single founder population, are all related, but Europeans, having mostly bred with other Europeans for millennia, are on average more closely related to other Europeans than they are to Africans or Asians, and vice versa. Because oceans, deserts, and mountain ranges have prevented people from choosing mates at random in the past, the large inbred families we call races are still discernible, each with a somewhat different distribution of gene frequencies. In theory, some of the varying genes could affect personality or intelligence (though any such differences would at most apply to averages, with vast overlap between the group members). This is not to say that such genetic differences are expected or that we have evidence for them, only that they are biologically possible.

(My own view, incidentally, is that in the case of the most discussed racial difference — the black-white IQ gap in the United States — the current evidence does not call for a genetic explanation. Thomas Sowell has documented that in most of the twentieth century and throughout the world, ethnic differences in IQ were the rule, not the exception.⁹ Members of minority groups who were out of the cultural mainstream commonly had average IQs that fell below that of the majority, including immigrants to the United States from southern and eastern Europe, the children of white mountaineers in the United States, children who grew up on canal boats in Britain, and Gaelic-speaking children in the Hebrides. The differences were at least as large as the current black-white gap but disappeared within a few generations. For many reasons, the experience of African Americans in the United States under slavery and segregation is not comparable to those of immigrants or rural isolates, and their transition to mainstream cultural patterns could easily take longer.)¹⁰

And then there are the sexes. Unlike ethnic groups and races, in which any differences are biologically minor and haphazard, the two sexes differ in at least one way that is major and systematic: they have different reproductive organs. On evolutionary grounds one might expect men and women to differ somewhat in the neural systems that control how they use those organs — in their sexuality, parental instincts, and mating tactics. By the same logic, one would expect them not to differ as much in the neural systems that deal with  {145}  the challenges both sexes face, such as those for general intelligence (as we will see in the chapter on gender).

~

So could discoveries in biology turn out to justify racism and sexism? Absolutely not! The case against bigotry is not a factual claim that humans are biologically indistinguishable. It is a moral stance that condemns judging an individual according to the average traits of certain groups to which the individual belongs. Enlightened societies choose to ignore race, sex, and ethnicity in hiring, promotion, salary, school admissions, and the criminal justice system because the alternative is morally repugnant. Discriminating against people on the basis of race, sex, or ethnicity would be unfair, penalizing them for traits over which they have no control. It would perpetuate the injustices of the past, in which African Americans, women, and other groups were enslaved or oppressed. It would rend society into hostile factions and could escalate into horrific persecution. But none of these arguments against discrimination depends on whether groups of people are or are not genetically indistinguishable.

Far from being conducive to discrimination, a conception of human nature is the reason we oppose it. Here is where the distinction between innate variation and innate universals is crucial. Regardless of IQ or physical strength or any other trait that can vary, all humans can be assumed to have certain traits in common. No one likes being enslaved. No one likes being humiliated. No one likes being treated unfairly, that is, according to traits that the person cannot control. The revulsion we feel toward discrimination and slavery comes from a conviction that however much people vary on some traits, they do not vary on these. This conviction contrasts, by the way, with the supposedly progressive doctrine that people have no inherent concerns, which implies that they could be conditioned to enjoy servitude or degradation.

The idea that political equality is a moral stance, not an empirical hypothesis, has been expressed by some of history's most famous exponents of equality. The Declaration of Independence proclaims, “We hold these truths to be self-evident; that all men are created equal.” The author, Thomas Jefferson, made it clear that he was referring to an equality of rights, not a biological sameness. For example, in an 1813 letter to John Adams he wrote: “I agree with you that there is a natural aristocracy among men. The grounds of this are virtue and talents.. .. For experience proves, that the moral and physical qualities of man, whether good or evil, are transmissible in a certain degree from father to son.”¹¹ (The fact that the Declaration originally was applied only to white men, and that Jefferson was far from an egalitarian in the conduct of his own life, does not change the argument. Jefferson defended political equality among white men — a novel idea in his time — even as he acknowledged innate differences among white men.) Similarly, Abraham Lincoln thought that the signers of the Declaration “did not mean to say all were equal in color, size,  {146}  intellect, moral development or social capacity,” but only in respect to “certain inalienable rights.”¹²

Some of the most influential contemporary thinkers about biology and human nature have drawn the same distinction. Ernst Mayr, one of the founders of the modern theory of evolution, wisely anticipated nearly four decades of debate when he wrote in 1963:

Equality in spite of evident nonidentity is a somewhat sophisticated concept and requires a moral stature of which many individuals seem to be incapable. They rather deny human variability and equate equality with identity. Or they claim that the human species is exceptional in the organic world in that only morphological characters are controlled by genes and all other traits of the mind or character are due to “conditioning” or other nongenetic factors. Such authors conveniently ignore the results of twin studies and of the genetic analysis of nonmorphological traits in animals. An ideology based on such obviously wrong premises can only lead to disaster. Its championship of human equality is based on a claim of identity. As soon as it is proved that the latter does not exist, the support of equality is likewise lost.¹³

Noam Chomsky made the same point in an article entitled “Psychology and Ideology.” Though he disagreed with Herrnstein's argument about IQ (discussed in Chapter 6), he denied the popular charge that Herrnstein was a racist and distanced himself from fellow radical scientists who were denouncing the facts as dangerous:

A correlation between race and IQ (were this shown to exist) entails no social consequences except in a racist society in which each individual is assigned to a racial category and dealt with not as an individual in his own right, but as a representative of this category. Herrnstein mentions a possible correlation between height and IQ. Of what social importance is that? None of course, since our society does not suffer under discrimination by height. We do not insist on assigning each adult to the category “below six feet in height” or “above six feet in height” when we ask what sort of education he should receive or where he should live or what work he should do. Rather, he is what he is, quite independent of the mean IQ of people of his height category. In a nonracist society, the category of race would be of no greater significance. The mean IQ of individuals of a certain racial background is irrelevant to the situation of a particular individual who is what he is....

It is, incidentally, surprising to me that so many commentators should find it disturbing that IQ might be heritable, perhaps largely so.  {147} 

Would it also be disturbing to discover that relative height or musical talent or rank in running the one-hundred-yard dash is in part genetically determined? Why should one have preconceptions one way or another about these questions, and how do the answers to them, whatever they may be, relate either to serious scientific issues (in the present state of our knowledge) or to social practice in a decent society?¹⁴

Some readers may not be reassured by this lofty stance. If all ethnic groups and both sexes were identical in all talents, then discrimination would simply be self-defeating, and people would abandon it as soon as the facts were known. But if they are not identical, it would be rational to take those differences into account. After all, according to Bayes’ theorem a decision maker who needs to make a prediction (such as whether a person will succeed in a profession) should factor in the prior probability, such as the base rate of success for people in that group. If races or sexes are different on average, racial profiling or gender stereotyping would be actuarially sound, and it would be naïve to expect information about race and sex not to be used for prejudicial ends. So a policy to treat people as individuals seems like a thin reed on which to hang any hope of reducing discrimination.

An immediate reply to this worry is that the danger arises whether the differences between groups are genetic or environmental in origin. An average is an average, and an actuarial decision maker should care only about what it is, not what caused it.

Moreover, the fact that discrimination can be economically rational would be truly dangerous only if our policies favored ruthless economic optimization regardless of all other costs. But in fact we have many policies that allow moral principles to trump economic efficiency. For example, it is illegal to sell your vote, sell your organs, or sell your children, even though an economist could argue that any voluntary exchange leaves both parties better off. These decisions come naturally in modern democracies, and we can just as resolutely choose public policies and private mores that disallow race and gender prejudice.¹⁵

Moral and legal proscriptions are not the only way to reduce discrimination in the face of possible group differences. The more information we have about the qualifications of an individual, the less impact a race-wide or sex-wide average would have in any statistical decision concerning that person. The best cure for discrimination, then, is more accurate and more extensive testing of mental abilities, because it would provide so much predictive information about an individual that no one would be tempted to factor in race or gender. (This, however, is an idea with no political future.)

Discrimination — in the sense of using a statistically predictive trait of an individual's group to make a decision about the individual — is not always  {148}  immoral, or at least we don't always treat it as immoral. To predict someone's behavior perfectly we would need an X-ray machine for the soul. Even predicting someone's behavior with the tools we do have — such as tests, interviews, background checks, and recommendations — would require unlimited resources if we were to use them to the fullest. Decisions that have to be made with finite time and resources, and which have high costs for certain kinds of errors, must use some trait as a basis for judging a person. And that necessarily judges the person according to a stereotype.

In some cases the overlap between two groups is so small that we feel comfortable discriminating against one of the groups absolutely. For example, no one objects to keeping chimpanzees out of our schools, even though it is conceivable that if we tested every chimp on the planet we might find one that could learn to read and write. We apply a speciesist stereotype that chimps cannot profit from a human education, figuring that the odds of finding an exception do not outweigh the costs of examining every last one.

In more realistic circumstances we have to decide on a case-by-case basis whether the discrimination is justifiable. Denying driving and voting rights to young teenagers is a form of age discrimination that is unfair to responsible teens. But we are not willing to pay either the financial costs of developing a test for psychological maturity or the moral costs of classification errors, such as teens wrapping their cars around trees. Almost everyone is appalled by racial profiling — pulling over motorists for “driving while black.” But after the 2001 terrorist attacks on the World Trade Center and the Pentagon, about half of Americans polled said they were not opposed to ethnic profiling — scrutinizing passengers for “flying while Arab.”¹⁶ People who distinguish the two must reason that the benefits of catching a marijuana dealer do not outweigh the harm done to innocent black drivers, but the benefits of stopping a suicide hijacker do outweigh the harm done to innocent Arab passengers. Cost-benefit analyses are also sometimes used to justify racial preferences: the benefits of racially diverse workplaces and campuses are thought to outweigh the costs of discriminating against whites.

The possibility that men and women are not the same in all respects also presents policymakers with choices. It would be reprehensible for a bank to hire a man over a woman as a manager for the reason that he is less likely to quit after having a child. Would it also be reprehensible for a couple to hire a woman over a man as a nanny for their daughter because she is less likely to sexually abuse the child? Most people believe that the punishment for a given crime should be the same regardless of who commits it. But knowing the typical sexual emotions of the two sexes, should we apply the same punishment to a man who seduces a sixteen-year-old girl and to a woman who seduces a sixteen-year-old boy?

These are some of the issues that face the people of a democracy in  {149}  deciding what to do about discrimination. The point is not that group differences may never be used as a basis for discrimination. The point is that they do not have to be used that way, and sometimes we can decide on moral grounds that they must not be used that way.

~

The Blank Slate, then, is not necessary to combat racism and sexism. Nor is it necessary to combat Social Darwinism, the belief that the rich and the poor deserve their status and so we must abandon any principle of economic justice in favor of extreme laissez-faire policies.

Because of a fear of Social Darwinism, the idea that class has anything to do with genes is treated by modern intellectuals like plutonium, even though it is hard to imagine how it could not be true in part. To adapt an example from the philosopher Robert Nozick, suppose a million people are willing to pay ten dollars to hear Pavarotti sing and are unwilling to pay ten dollars to hear me sing, in part because of genetic differences between us. Pavarotti will be ten million dollars richer and will live in an economic stratum that my genes keep me out of, even in a society that is totally fair.¹⁷ It is a brute fact that greater rewards will go to people with greater inborn talent if other people are willing to pay more for the fruits of those talents. The only way that cannot happen is if people are locked into arbitrary castes, if all economic transactions are controlled by the state, or if there is no such thing as inborn talent because we are blank slates.

A surprising number of intellectuals, particularly on the left, do deny that there is such a thing as inborn talent, especially intelligence. Stephen Jay Gould's 1981 bestseller The Mismeasure of Man was written to debunk “the abstraction of intelligence as a single entity, its location within the brain, its quantification as one number for each individual, and the use of these numbers to rank people in a single series of worthiness, invariably to find that oppressed and disadvantaged groups — races, classes, or sexes — are innately inferior and deserve their status.”¹⁸ The philosopher Hilary Putnam argued that the concept of intelligence is part of a social theory called “elitism” that is specific to capitalist societies:

Under a less competitive form of social organization, the theory of elitism might well be replaced by a different theory — the theory of egalitarianism. This theory might say that ordinary people can do anything that is in their interest and do it well when (1) they are highly motivated, and (2) they work collectively.¹⁹

In other words, any of us could become a Richard Feynman or a Tiger Woods if only we were highly enough motivated and worked collectively.

I find it truly surreal to read academics denying the existence of intelligence. Academics are obsessed with intelligence. They discuss it endlessly in  {150}  considering student admissions, in hiring faculty and staff, and especially in their gossip about one another. Nor can citizens or policymakers ignore the concept, regardless of their politics. People who say that IQ is meaningless will quickly invoke it when the discussion turns to executing a murderer with an IQ of 64, removing lead paint that lowers a child's IQ by five points, or the presidential qualifications of George W. Bush. In any case, there is now ample evidence that intelligence is a stable property of an individual, that it can be linked to features of the brain (including overall size, amount of gray matter in the frontal lobes, speed of neural conduction, and metabolism of cerebral glucose), that it is partly heritable among individuals, and that it predicts some of the variation in life outcomes such as income and social status.²⁰

The existence of inborn talents, however, does not call for Social Darwinism. The anxiety that one must lead to the other is based on two fallacies. The first is an all-or-none mentality that often infects discussions of the social implications of genetics. The likelihood that inborn differences are one contributor to social status does not mean that it is the only contributor. The other ones include sheer luck, inherited wealth, race and class prejudice, unequal opportunity (such as in schooling and connections), and cultural capital: habits and values that promote economic success. Acknowledging that talent matters doesn't mean that prejudice and unequal opportunity do not matter.

But more important, even if inherited talents can lead to socioeconomic success, it doesn't mean that the success is deserved in a moral sense. Social Darwinism is based on Spencer's assumption that we can look to evolution to discover what is right — that “good” can be boiled down to “evolutionarily successful.” This lives in infamy as a reference case for the “naturalistic fallacy”: the belief that what happens in nature is good. (Spencer also confused people's social success — their wealth, power, and status — with their evolutionary success, the number of their viable descendants.) The naturalistic fallacy was named by the moral philosopher G. E. Moore in his 1903 Principia Ethica, the book that killed Spencer's ethics.²¹ Moore applied “Hume's Guillotine,” the argument that no matter how convincingly you show that something is true, it never follows logically that it ought to be true. Moore noted that it is sensible to ask, “This conduct is more evolutionarily successful, but is it good?” The mere fact that the question makes sense shows that evolutionary success and goodness are not the same thing.

Can one really reconcile biological differences with a concept of social justice? Absolutely. In his famous theory of justice, the philosopher John Rawls asks us to imagine a social contract drawn up by self-interested agents negotiating under a veil of ignorance, unaware of the talents or status they will inherit at birth — ghosts ignorant of the machines they will haunt. He argues that a just society is one that these disembodied souls would agree to be born into, knowing that they might be dealt a lousy social or genetic hand.²² If you agree  {151}  that this is a reasonable conception of justice, and that the agents would insist on a broad social safety net and redistributive taxation (short of eliminating incentives that make everyone better off), then you can justify compensatory social policies even if you think differences in social status are 100 percent genetic. The policies would be, quite literally, a matter of justice, not a consequence of the indistinguishability of individuals.

Indeed, the existence of innate differences in ability makes Rawls's conception of social justice especially acute and eternally relevant. If we were blank slates, and if a society ever did eliminate discrimination, the poorest could be said to deserve their station because they must have chosen to do less with their standard-issue talents. But if people differ in talents, people might find themselves in poverty in a nonprejudiced society even if they applied themselves to the fullest. That is an injustice that, a Rawlsian would argue, ought to be rectified, and it would be overlooked if We didn't recognize that people differ in their abilities.

~

Some people have suggested to me that these grandiloquent arguments are just too fancy for the dangerous world we live in. Granted, there is evidence that people are different, but since data in the social sciences are never perfect, and since a conclusion of inequality might be used to the worst ends by bigots or Social Darwinists, shouldn't we err on the side of caution and stick with the null hypothesis that people are identical? Some believe that even if we were certain that people differ genetically, we might still want to promulgate the fiction that they are the same, because it is less open to abuse.

This argument is based on the fallacy that the Blank Slate has nothing but good moral implications and a theory of human nature nothing but bad ones. In the case of human differences, as in the case of human universals, the dangers go both ways. If people in different stations are mistakenly thought to differ in their inherent ability, we might overlook discrimination and unequal opportunity. In Darwin's words, “If the misery of the poor be caused not by the laws of nature, but by our institutions, great is our sin.” But if people in different stations are mistakenly thought to be the same, then we might envy them the rewards they've earned fair and square and might implement coercive policies to hammer down the nails that stick up. The economist Friedrich Hayek wrote, “It is just not true that humans are born equal;... if we treat them equally, the result must be inequality in their actual position; ... [thus] the only way to place them in an equal position would be to treat them differently. Equality before the law and material equality are, therefore, not only different but in conflict with each other.”²³ The philosophers Isaiah Berlin, Karl Popper, and Robert Nozick have made similar points.

Unequal treatment in the name of equality can take many forms. Some  {152}  forms have both defenders and detractors, such as soak-the-rich taxation, heavy estate taxes, streaming by age rather than ability in schools, quotas and preferences that favor certain races or regions, and prohibitions against private medical care or other voluntary transactions. But some can be downright dangerous. If people are assumed to start out identical but some end up wealthier than others, observers may conclude that the wealthier ones must be more rapacious. And as the diagnosis slides from talent to sin, the remedy can shift from redistribution to vengeance. Many atrocities of the twentieth century were committed in the name of egalitarianism, targeting people whose success was taken as evidence of their criminality. The kulaks (“bourgeois peasants”) were exterminated by Lenin and Stalin in the Soviet Union; teachers, former landlords, and “rich peasants” were humiliated, tortured, and murdered during China's Cultural Revolution; city dwellers and literate professionals were worked to death or executed during the reign of the Khmer Rouge in Cambodia.²⁴ Educated and entrepreneurial minorities who have prospered in their adopted regions, such as the Indians in East Africa and Oceania, the Ibos in Nigeria, the Armenians in Turkey, the Chinese in Indonesia and Malaysia, and the Jews almost everywhere, have been expelled from their homes or killed in pogroms because their visibly successful members were seen as parasites and exploiters.²⁵

A nonblank slate means that a tradeoff between freedom and material equality is inherent to all political systems. The major political philosophies can be defined by how they deal with the tradeoff. The Social Darwinist right places no value on equality; the totalitarian left places no value on freedom. The Rawlsian left sacrifices some freedom for equality; the libertarian right sacrifices some equality for freedom. While reasonable people may disagree about the best tradeoff, it is unreasonable to pretend there is no tradeoff. And that in turn means that any discovery of innate differences among individuals is not forbidden knowledge to be suppressed but information that might help us decide on these tradeoffs in an intelligent and humane manner.

~

The specter of eugenics can be disposed of as easily as the specters of discrimination and Social Darwinism. Once again, the key is to distinguish biological facts from human values.

If people differ genetically in intelligence and character, could we selectively breed for smarter and nicer people? Possibly, though the intricacies of genetics and development would make it far harder than the fans of eugenics imagined. Selective breeding is straightforward for genes with additive effects — that is, genes that have the same impact regardless of the other genes in the genome. But some traits, such as scientific genius, athletic virtuosity, and musical giftedness, are what behavioral geneticists call emergenic: they materialize only with certain combinations of genes and therefore don't “breed true.”²⁶ Moreover, a given gene can lead to different behavior in different  {153}  environments. When the biochemist (and radical scientist) George Wald was solicited for a semen sample by William Shockley's sperm bank for Nobel Prize — winning scientists, he replied, “If you want sperm that produces Nobel Prize winners you should be contacting people like my father, a poor immigrant tailor. What have my sperm given the world? Two guitarists!”²⁷

Whether or not we can breed for certain traits, should we do it? It would require a government wise enough to know which traits to select, knowledgeable enough to know how to implement the breeding, and intrusive enough to encourage or coerce people's most intimate decisions. Few people in a democracy would grant their government that kind of power even if it did promise a better society in the future. The costs in freedom to individuals and in possible abuse by authorities are unacceptable.

Contrary to the belief spread by the radical scientists, eugenics for much of the twentieth century was a favorite cause of the left, not the right.²⁸ It was championed by many progressives, liberals, and socialists, including Theodore Roosevelt, H. G. Wells, Emma Goldman, George Bernard Shaw, Harold Laski, John Maynard Keynes, Sidney and Beatrice Webb, Margaret Sanger, and the Marxist biologists J. B. S. Haldane and Hermann Muller. It's not hard to see why the sides lined up this way. Conservative Catholics and Bible Belt Protestants hated eugenics because it was an attempt by intellectual and scientific elites to play God. Progressives loved eugenics because it was on the side of reform rather than the status quo, activism rather than laissez-faire, and social responsibility rather than selfishness. Moreover, they were comfortable expanding state intervention in order to bring about a social goal. Most abandoned eugenics only when they saw how it led to forced sterilizations in the United States and Western Europe and, later, to the policies of Nazi Germany. The history of eugenics is one of many cases in which the moral problems posed by human nature cannot be folded into familiar left-right debates but have to be analyzed afresh in terms of the conflicting values at stake.

~

The most sickening associations of a biological conception of human nature are the ones to Nazism. Though the opposition to the idea of a human nature began decades earlier, historians agree that bitter memories of the Holocaust were the main reason that human nature became taboo in intellectual life after World War II.

Hitler was undeniably influenced by the bastardized versions of Darwinism and genetics that were popular in the early decades of the twentieth century, and he specifically cited natural selection and the survival of the fittest in laying out his poisonous doctrine. He believed in an extreme Social Darwinism in which groups were the unit of selection and a struggle among groups was necessary for national strength and vigor. He believed that the groups were constitutionally distinct races, that their members shared a distinctive  {154}  biological makeup, and that they differed from one another in strength, courage, honesty, intelligence, and civic-mindedness. He wrote that the extinction of inferior races was part of the wisdom of nature, that the superior races owed their vitality and virtue to their genetic purity, and that the superior races were in danger of being degraded by interbreeding with the inferior ones. He used these beliefs to justify his war of conquest and his genocide of Jews, Gypsies, Slavs, and homosexuals.²⁹

The misuse of biology by the Nazis is a reminder that perverted ideas can have horrifying consequences and that intellectuals have a responsibility to take reasonable care that their ideas not be misused for evil ends. But part of that responsibility is not to trivialize the horror of Nazism by exploiting it for rhetorical clout in academic catfights. Linking the people you disagree with to Nazism does nothing for the memory of Hitler's victims or for the effort to prevent other genocides. It is precisely because these events are so grave that we have a special responsibility to identify their causes precisely.

An idea is not false or evil because the Nazis misused it. As the historian Robert Richards wrote of an alleged connection between Nazism and evolutionary biology, “If such vague similarities suffice here, we should all be hustled to the gallows.”³⁰ Indeed, if we censored ideas that the Nazis abused, we would have to give up far more than the application of evolution and genetics to human behavior. We would have to censor the study of evolution and genetics, period. And we would have to suppress many other ideas that Hitler twisted into the foundations of Nazism:

• The germ theory of disease: The Nazis repeatedly cited Pasteur and Koch to argue that the Jews were like an infectious bacillus that had to be eradicated to control a contagious disease.

• Romanticism, environmentalism, and the love of nature: The Nazis amplified a Romantic strain in German culture that believed the Volk were a people of destiny with a mystical bond to nature and the land. The Jews and other minorities, in contrast, took root in the degenerate cities.

• Philology and linguistics: The concept of the Aryan race was based on a prehistoric tribe posited by linguists, the Indo-Europeans, who were thought to have spilled out of an ancient homeland thousands of years ago and to have conquered much of Europe and Asia.

• Religious belief: Though Hitler disliked Christianity, he was not an atheist, and was emboldened by the conviction that he was carrying out a divinely ordained plan.³¹

The danger that we might distort our own science as a reaction to the Nazis’ distortions is not hypothetical. The historian of science Robert Proctor has shown that American public health officials were slow to acknowledge that  {155}  smoking causes cancer because it was the Nazis who had originally established the link.³² And some German scientists argue that biomedical research has been crippled in their country because of vague lingering associations to Nazism.³³

Hitler was evil because he caused the deaths of thirty million people and conceivable suffering to countless others, not because his beliefs made reference to biology (or linguistics or nature or smoking or God). Smearing the guilt from his actions to every conceivable aspect of his factual beliefs can only backfire. Ideas are connected to other ideas, and should any of Hitler's turn out to have some grain of truth — if races, for example, turn out to have any biological reality, or if the Indo-Europeans really were a conquering tribe — we would not want to concede that Nazism wasn't so wrong after all.

The Nazi Holocaust was a singular event that changed attitudes toward countless political and scientific topics. But it was not the only ideologically inspired holocaust in the twentieth century, and intellectuals are only beginning to assimilate the lessons of the others: the mass killings in the Soviet Union, China, Cambodia, and other totalitarian states carried out in the name of Marxism. The opening of Soviet archives and the release of data and memoirs on the Chinese and Cambodian revolutions are forcing a reevaluation of the consequences of ideology as wrenching as that following World War II. Historians are currently debating whether the Communists’ mass executions, forced marches, slave labor, and man-made famines led to one hundred million deaths or “only” twenty-five million. They are debating whether these atrocities are morally worse than the Nazi Holocaust or “only” the equivalent.³⁴

And here is the remarkable fact: though both Nazi and Marxist ideologies led to industrial-scale killing, their biological and psychological theories were opposites. Marxists had no use for the concept of race, were averse to the notion of genetic inheritance, and were hostile to the very idea of a human nature rooted in biology.³⁵ Marx and Engels did not explicitly embrace the doctrine of the Blank Slate in their writings, but they were adamant that human nature has no enduring properties. It consists only in the interactions of groups of people with their material environments in a historical period, and constantly changes as people change their environment and are simultaneously changed by it.³⁶ The mind therefore has no innate structure but emerges from the dialectical processes of history and social interaction. As Marx put it:

All history is nothing but a continuous transformation of human nature.³⁷

Circumstances make men just as much as men make circumstances.³⁸

The mode of production of material life conditions the social, political, and intellectual life processes in general. It is not the consciousness of  {156}  men that determines their being, but, on the contrary, their social being that determines their consciousness.³⁹

In a foreshadowing of Durkheim's and Kroeber's insistence that individual human minds are not worthy of attention, Marx wrote:

Man is not an abstract being, squatting outside the world. Man is the world of men, the State and Society. The essence of man is not an abstraction inherent in each particular individual. The real nature of man is the totality of social relations.⁴⁰

Individuals are dealt with only in so far as they are the personifications of economic categories, embodiments of particular class-relations and class interests.⁴¹

[Death] seems to be a harsh victory of the species over the particular individual and to contradict their unity. But the particular individual is only a particular species-being, and as such mortal.⁴²

Marx's twentieth-century followers did embrace the Blank Slate, or a: least the related metaphor of malleable material. Lenin endorsed Nikolai Bukharin's ideal of “the manufacturing of Communist man out of the human material of the capitalist age.”⁴³ Lenin's admirer Maxim Gorky wrote, “The working classes are to Lenin what minerals are to the metallurgist”⁴⁴ and “Human raw material is immeasurably more difficult to work with than wood” (the latter while admiring a canal built by slave labor).⁴⁵ We come across the metaphor of the blank slate in the writings of a man who may have been responsible for sixty-five million deaths:

A blank sheet of paper has no blotches, and so the newest and most beautiful words can be written on it, the newest and most beautiful pictures can be painted on it.

— Mao Zedong⁴⁶

And we find it in a saying of a political movement that killed a quarter of its countrymen:

Only the newborn baby is spotless.

— Khmer Rouge slogan⁴⁷

The new realization that government-sponsored mass murder can come from an anti-innatist belief system as easily as from an innatist one upends the postwar understanding that biological approaches to behavior are uniquely  {157}  sinister. An accurate appraisal of the cause of state genocides must look for beliefs common to Nazism and Marxism that launched them on their parallel trajectories, and for the beliefs specific to Marxism that led to the unique atrocities committed in its name. A new wave of historians and philosophers is doing exactly that.⁴⁸

Nazism and Marxism shared a desire to reshape humanity. “The alteration of men on a mass scale is necessary,” wrote Marx; “the will to create mankind anew” is the core of National Socialism, wrote Hitler.⁴⁹ They also shared a revolutionary idealism and a tyrannical certainty in pursuit of this dream, with no patience for incremental reform or adjustments guided by the human consequences of their policies. This alone was a recipe for disaster. As Aleksandr Solzhenitsyn wrote in The Gulag Archipelago, “Macbeth's self-justifications were feeble — and his conscience devoured him. Yes, even Iago was a little lamb too. The imagination and the spiritual strength of Shakespeare's evildoers stopped short at a dozen corpses. Because they had no ideology”

The ideological connection between Marxist socialism and National Socialism is not fanciful.⁵⁰ Hitler read Marx carefully while living in Munich in 1913, and may have picked up from him a fateful postulate that the two ideologies would share.⁵¹ It is the belief that history is a preordained succession of conflicts between groups of people and that improvement in the human condition can come only from the victory of one group over the others. For the Nazis the groups were races; for the Marxists they were classes. For the Nazis the conflict was Social Darwinism; for the Marxists, it was class struggle. For the Nazis the destined victors were the Aryans; for the Marxists, they were the proletariat. The ideologies, once implemented, led to atrocities in a few steps: struggle (often a euphemism for violence) is inevitable and beneficial; certain groups of people (the non-Aryan races or the bourgeoisie) are morally inferior; improvements in human welfare depend on their subjugation or elimination. Aside from supplying a direct justification for violent conflict, the ideology of intergroup struggle ignites a nasty feature of human social psychology: the tendency to divide people into in-groups and out-groups and to treat the out-groups as less than human. It doesn't matter whether the groups are thought to be defined by their biology or by their history. Psychologists have found that they can create instant intergroup hostility by sorting people on just about any pretext, including the flip of a coin.⁵²

The ideology of group-against-group struggle explains the similar outcomes of Marxism and Nazism. The ideology of the Blank Slate helps explain some of the features that were unique to the Marxist states:

• If people do not differ in psychological traits like talent or drive, then anyone who is better off must be avaricious or larcenous (as I mentioned  {158}  earlier). Massive killing of kulaks and “rich” or “bourgeois” peasants was a feature of Lenin's and Stalin's Soviet Union, Mao's China, and Pol Pot's Cambodia.