Nature Via Nurture: Genes, Experience, and What Makes Us Human

Citation preview

NATURE

VIA

NURTURE Genes, What

Experience, Makes

Us

Human

Matt Ridley

.,. HarperCollinsPublishers

and

NATURE VIA NURTURE. Copyright

© 2003 Matt Ridley. All rights reserved. Printed in the

United States of America. No part of this book may be used or reproduced in any man­ ner whatsoever without written permission except in the case of bnef quotations embod­ ied in cntIcal articles and reviews. For information, address HarperCollins PublIshers Inc., 10 East 53rd Street, New York, NY 10022. HarperCollIns books may be purchased for educational, business, or sales promotional use. For information, please write: Special Markets Department, HarperCollins Publishers Inc., 10 East 53rd Street, New York, NY 10022. FIRST EDITION

PublIshed in Great BritaIn in 2003 by Fourth Estate, a Division of HarperCollins PublIshers Inc. Printed on acid-free paper LIbrary of Congress Catalogtng-in-PublicatIon Data RIdley, Matt. Nature via nurture: genes, experience, and what makes us human

/ Matt RIdley.-1st ed. p.

cm.

Includes biblIographical references (p. ). ISBN 0-06-000678-1 1. Nature and nurture.

2. Human genetics.

1. Title.

QH438.5.R535 2003 155 ·7--dC21 2003040687 03 04 05 06 07

NMSG / RRD

10 9 8 7 6 5 4 3 2

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For Jim

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O

N T E

N

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Prologue: Twelve Hairy Men I.

2. 3· 4· 5· 6. 7· 8. 9· 1 0.

The Paragon of Animals A Plethora of Instincts A Convenient Jingle The Madness of Causes Genes in the Fourth Dimension Formative Years Learning Lessons Conundrums o f Culture The Seven Meanings of "Gene" A Budget of Paradoxical Morals Epilogue: l-lomo stramineus: The Straw Man Acknowledgmen ts Endnotes Index

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7 38 69 98 125 151 1 77 20 1 23 1 249 277 28 1 283 3 07

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Perverse Mankind! Whose wills, created free, Charge all their woes on absolute Decree; All to the dooming Gods their guilt translate, And follies are miscall'd the crimes of Fate. Homer's Ocfyssey, translated by Alexander Pope 1

"Revealed: the secret of human behaviour," read the banner headline in the British Sunday newspaper the Obseroer on 1 1 February 200 1 . "Environment, not genes, key to our acts." The source of the story was Craig Venter, the self-made man of genes who had built a private company to read the full sequence of the human genome (his own) in competition with an international consortium funded by taxes and charities. That sequence-a string of three billion letters composed in a four-letter alphabet containing the complete recipe for building and running a human body-was to be published later in the week. The first analysis had revealed that there were just 3 0,000 genes in the human genome, not the 1 00,000 that many had been estimating up until a few months before. Details had already been circulated to journalists, though under an

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embargo. But Venter spilled the story at an open meeting in Lyon on 9 February. Robin McKie of the Obseroerwas in the audience and rec­ ognized at once that the figure 30,000 was now public. He went up to Venter and asked him if he realized that this broke the embargo; he did. Not for the first time in the increasingly bitter rivalry over the genome project, Venter's version of the story would hit the headlines before that of his rivals. "We simply do not have enough genes for this idea of biological determinism to be right," Venter said to McKie. "The wonderful diversity of the human species is not hard-wired in our genetic code. Our environments are critical."2 Seeing the Obseroer's first edition, other newspapers followed suit. "Genome discovery shocks scientists: genetic blueprint contains far fewer genes than thought-DN A 's importance downplayed," pro­ claimed the San Francisco Chronicle later that Sunday.3 The scientific journals promptly lifted the embargo and the story was in newspapers around the world. "Analysis of human genome discovers far fewer genes," intoned the New York Times.4 Not only had McI Though he stressed the influence of the environment, Boas was no extreme blank-slater. He made the crucial distinction between the individual and the race. It was precisely because he recognized profound innate differences in personality between individuals that he discounted innate differences between races, a perspective that was later proved genetically correct by Richard Lewontin. The genetic differences between two individuals chosen at random from one race are far greater than the average differences between races. Indeed, Boas sounds thoroughly modern in almost every way. His fervent antiracism, his belief that culture determined rather than reflected eth­ nic idiosyncrasy, and his passion for equality of opportunity for all would come to be hallmarks of political virtue in the second half of the century, although Boas himself was dead by then. As usual, some of Boas's followers went too far. They gradually abandoned his belief in individual differences and his recognition of universal features of human nature. They made the usual mistake of equating the truth of one proposition with the falsehood of another. Because culture influenced behavior, innateness could not do so. Margaret Mead was initially the most egregious in this respect. Her studies of the sexual mores of Samoans purported to show how ethnocentric, and therefore "cultural," was the western practice of premarital celibacy, with the associated inhibitions about sex. In fact, it is now known that she had been duped by a handful of prank-playing young women during her all too brief visit to the island, and that Samoa in the I 9 20S was if anything slightly more censorious about sex than America.7 The damage had been done, though, and anthropol­ ogy, like psychology under Watson and Skinner, became devoted to the blank slate-to the notion that all of human behavior was a prod­ uct of the social environment alone.

CONUNDRUMS

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20 5

In parallel with Boas's reformation of anthropology, the same theme was coming to dominate the new science of sociology. Boas's exact contemporary, and his match in the mustache department, Emile Durkheim, made an even stronger statement of social causa­ tion: social phenomena could be explained by social facts alone, not by anything biological. Omnia cultura ex cultura. Durkheim, who was a year older than Boas, was born in Lorraine, just across the French border from Boas's birthplace, also to Jewish parents . Unlike Boas, however, Durkheim was the son of a rabbi, descended from a long line of rab­ bis, and his youth was spent in the study of the Talmud. After flirting with Catholicism, he entered the elite Ecole Normale Superieure in Paris. Whereas Boas would wander around the world, live in igloos, befriend Native Americans, and emigrate, Durkheim did little except study, write, and argue. Aside from a brief period of study in Germany, he remained in the ivory tower of French universities all his life, first in Bordeaux and later in Paris. He is a biographical desert. Yet Durkheim's influence upon the nascent school of sociology was immense. It was he who predicated the study of sociology on the notion of the blank slate. The causes of human behavior-from sexual jealousy to mass hysteria-are outside the individual. Social phenom­ ena are real, repeatable, definable, and scientific (Durkheim envied the physicists their hard facts-physics envy is a well-known condition in the softer sciences), but they are not reducible to biology. Human nature is the consequence, not the cause, of social forces. The general characteristics of human nature participate in the work of elaboration from which social life results. But they are not the cause of it, nor do they give it its special form; they only make it possible. Collective representations, emotions, and tendencies are caused not by certain states of the consciousnesses of individuals but by the conditions in which the social group, in its totality, is placed . . . . Individual natures are merely the indeterminate material that the social factor molds and trans forms.8

Boas and Durkheim, with Watson in psychology, represent the zenith of the blank-slate argument for the perfect malleability of human psychology by outside forces. As a negative statement rejecting

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all innateness, it is an argument that has been so demolished by Steven Pinker in his recent book The Blank Slate as to leave little to say.9 But as a positive statement of the degree to which human beings are influ­ enced by social factors, it is undeniable. The brick that Durkheim helped Boas put into the wall of human nature was a vital one-the brick called culture. Boas disposed of the notion that all human soci­ eties consisted of more or less well trained apprentices aspiring to be English gentlemen, that there was a ladder of stages through which cul­ tures must pass on the way to civilization. In its place, he posited a uni­ versal human nature refracted by different traditions into separate cultures. The behavior of a human being owes much to his nature; but it also owes much to the rituals and habits of his fellows. He seems to absorb something from the tribe. Boas posed, and still poses, a paradox. If human abilities are the same everywhere, and Germans and Inuit have equal minds, then why are cultures diverse at all? Why is there not a single human culture common to Baffinland and the Rhineland? Alternatively, if culture, not nature, is responsible for creating different societies, then how can they be regarded as equal? The very fact of cultural change implies that some cultures can advance more than others, and if culture influences the mind, then some cultures must produce superior minds. Boas's intellectual descendants, such as Clifford Geertz, have addressed the paradox by asserting that the universals must be trivial; there is no "mind for all cultures," no common core to the human psyche at all save the obvious senses . Anthropology must concern itself with difference, not similarity. This answer I find deeply unsatisfying, not least because of its obvious political dangers-without Boas's conclusion of mental equality, in by the back door comes prejudice. That would be to com­ mit the naturalistic fallacy-deriving morals from facts, or "ought" from "is"-which the GOD forbid. It also commits the fallacy of determinism, ignoring the lessons of chaos theory: set rules need not produce a set result. With the sparse rules of chess, you can produce trillions of different games within just a few moves.

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I do not believe Boas ever put it like this, but the logical conclusion from his position is that there is a great contrast between technological advance and mental stasis. Boas 's own culture had steamships, tele­ graphs, and literature; but it produced no discernible superiority in spirit and sensibility over the illiterate Inuit hunter-gatherers. This was a theme that ran through the work of Boas's contemporary, the novel­ ist Joseph Conrad. Progress, for Conrad, was a delusion. Human nature never progressed but was doomed to repeat the same atavisms in each generation. There is a universal human nature, retreading the triumphs and disasters of its ancestors. Technology and tradition merely refract this nature into the local culture: bow ties and violins in one place, nasal ornaments and tribal dancing in another. But the bow ties and the dances do not shape the mind-they express it. When watching a Shakespeare play, I am often struck by the sophis­ tication of his understanding of personality. There is nothing naive or primitive about the way his characters scheme or woo; they are world­ weary, jaded, postmodernist, or self-aware. Think of the cynicism of Beatrice, Iago, Edmund, or Jaques. I cannot help thinking, for a split second, that this seems odd. The weapons they fight with are primi­ tive, their methods of travel cumbersome, their plumbing antedi­ luvian. Yet they speak to us of love and despair and anger and betrayal in voices of modern complexity and subtlety. How can this be? Their author had such cultural disadvantages. He had not read Jane Austen or Dostoyevsky; or watched Woody Allen; or seen a Picasso; or lis­ tened to Mozart; or heard of relativity; or flown in an airplane; or surfed the Net. Far from proving the plasticity of human nature, Boas's very argument for the equality of cultures depends upon accepting an unchanging, universal nature. Culture can determine itself, but it can­ not determine human nature. Ironically, it was Margaret Mead who proved this most clearly. To find a society in which young girls were sexually uninhibited, she had to visit a land of the imagination. Like Rousseau before her, she sought something "primitive" about human nature in the South Seas. But there is no primitive human nature. Her

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failure to discover the cultural determinism o f human nature is the dog that failed to bark. So turn the determinism around and ask why human nature seems to be universally capable of producing culture-of generating cumula­ tive, technological, heritable traditions . Equipped with just snow, dogs, and dead seals, human beings will gradually invent a lifestyle complete with songs and gods as well as sleds and igloos. What is it inside the human brain that enables it to achieve this feat, and when did this talent appear? Notice, first, that the generation of culture is a social activity. A solitary human mind cannot secrete culture. The precocious Russian anthropologist Lev Semenovich Vygotsky pointed out in the 1 9 20S that to describe an isolated human mind is to miss the point. Human minds are never isolated. More than those of any other species, they swim in a sea called culture. They learn languages, they use technolo­ gies, they observe rituals, they share beliefs, they acquire skills. They have a collective as well as an individual experience; they even share collective intentionality. Vygotsky, who died at the age of 3 8 in 1 9 34 after publishing his ideas only in Russian, remained largely unknown in the West until much later. He has recently become a fashionable fig­ ure in educational psychology and some corners of anthropology. For my purposes, however, his most important insight is his insistence on a link between the use of tools and language. to If I am to sustain my argument that genes are at the root of nurture as well as nature, then I must somehow explain how genes make culture possible. Once again, I intend to do so, not by proposing "genes for" cultural practice, but by proposing the existence of genes that respond to the environment-of genes as mechanisms, not causes. This is a tall order, and I may as well admit, right now, that I will fail. I believe that the human capacity for culture comes not from some genes that co-evolved with human culture, but from a fortuitous set of preadaptations that suddenly endowed the human mind with an almost limitless capacity to accumulate and transmit ideas. Those preadaptations are underpinned by genes.

CONUNDRUMS

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K N O W L ED GE

The discovery that human beings are 9 5 percent chimpanzee at the genetic level exacerbates my problem. In describing the genes involved in learning, instinct, imprinting, and development, I had no difficulty calling on animals as examples, for the difference between human and animal psychology in these respects is a difference of degree. But culture is different. The cultural gap between a human being and even the brightest ape or dolphin is a gulf. Turning an ancestral ape's brain into a human brain plainly took just a handful of minor adjustments to the recipe: all the same ingredients, just a little longer in the oven. Yet these minor changes had far-reaching consequences: people have nuclear weapons and money, gods and poetry, philosophy and fire. They got all these things through culture, through their ability to accumulate ideas and inventions generation by generation, transmit them to others, and thereby pool the cognitive resources of many individuals alive and dead. Ordinary modern businesspeople, for instance, could not do without the help of Assyrian phonetic script, Chinese printing, Arabic algebra, Indian numerals, Italian double-entry bookkeeping, Dutch merchant law, Californian integrated circuits, and a host of other inventions spread over continents and centuries. What is it that makes people, and not chimps, capable of this feat of accumulation? After all, there seems little doubt that chimpanzees are capable of culture. They show strong local traditions in feeding behavior, which are then passed on by social learning. Some populations crack nuts using stones; others use sticks. In west Africa, chimps eat ants by dipping a short stick into an ants' nest and putting each ant to the mouth one by one; in east Africa, they dip a long stick into an ants' nest, collect many ants on it, and strip the ants off the stick into the hand and from there to the mouth. There are more than 5 0 known cultural traditions of this kind across Africa, and each is learned by careful observation by youngsters (adult immigrants to a troop find it harder to learn local customs) . These traditions are vital to their lives.

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Frans de Waal goes so far as to say that "chimps are completely dependent on culture for survival." Like human beings, they cannot get through life without learned traditions . 1 1 Nor are chimpanzees alone in this. The moment when animal culture was first discovered was in September 1 9 5 3 , on the tiny island of Kohima, off the coast of Japan. A young woman named Satsue Mito had for five years been feeding the monkeys on the islet with wheat and sweet potatoes to habituate them to human observers. That month she first saw a young monkey called Imo wash the sand off a sweet potato. Within three months two of Imo's playmates and her mother had adopted the practice, and within five years most younger monkeys in the troop had joined them. Only the older males failed to take up the custom. Imo soon learned to separate wheat from sand by putting it in water and letting the sand sink. 12 Culture abounds in large-brained species. I