Book: The Agile Gene

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When, as by a miracle, the lovely butterfly bursts from the chrysalis full-winged and perfect … it has, for the most part, nothing to learn, because its little life flows from its organization like melody from a music box.

Douglas Alexander Spalding, 1873

Like Charles Darwin, William James was a man of independent means. He inherited a private income from his father, Henry, whose own father (another William) had amassed $10,000 a year from the Erie Canal. The one-legged Henry used his self-sufficiency to become an intellectual, and spent much of his life shuttling between New York, Geneva, London, and Paris with his children in tow. He was articulate, religious, and self-assured. His two youngest sons went off to fight in the Civil War, then failed in business and turned to drink or depression. His two eldest sons, William and Henry, were trained almost from birth to be intellectuals. The result was (in Rebecca West’s phrase) that “one of them grew up to write fiction as though it were philosophy and the other to write philosophy as though it were fiction.”

Both brothers were influenced by Darwin. Henry’s novel The Portrait of a Lady was written in thrall to Darwin’s idea of female choice as a force in evolution. William’s Principles of Psychology, much of which was first published as a series of articles in the 1880s, contained a manifesto for nativism—the idea that the mind cannot learn unless it has the rudiments of innate knowledge. In this, William James went against the prevailing fashion for empiricism, the theory that behavior is shaped by experience. He believed that human beings were equipped with innate tendencies that were derived not from experience but from the Darwinian process of natural selection. “He denies experience!” wrote James, quoting an imaginary reader. “Denies science; believes the mind created by miracle; is a regular old partisan of innate ideas! That is enough! We’ll listen to such antediluvian twaddle no more.”

William James asserted that human beings have more instincts than other animals, not fewer. “Man possesses all the impulses that [lower creatures] have, and a great many more besides…. It will be observed that no other mammal, not even the monkey, shows so large an array.” He argued that it was false to oppose instinct to reason:

Reason, per se, can inhibit no impulses; the only thing that can neutralize an impulse is an impulse the other way. Reason may, however, make an inference which will excite the imagination so as to set loose the impulse the other way; and thus, though the animal richest in reason might also be the animal richest in instinctive impulses, too, he would never seem the fatal automaton which a merely instinctive animal would be.

This is an extraordinary passage, not least because its impact on early-twenty-first-century thought can be said to be almost nil. Very few people, on the side of either nature or nurture, took up such an extreme nativist position in the century to come; almost everybody assumed for the following hundred years that reason was indeed the opposite of instinct. Yet James was no fringe lunatic. His work has influenced generations of scholars on consciousness, sensation, space, time, memory, will, emotion, thought, knowledge, reality, self, morality, and religion—to name just the chapter headings of a modern book about his work. So why does this same book of 628 pages not even list the words “instinct,” “impulse,” or “innate” in its index? Why, for more than a century, has it been considered little short of indecent even to use the word “instinct” in the context of human behavior?

James’s ideas were immensely influential at first. His follower William McDougall founded a whole school of instinctivists, who became adept at spotting new human instincts for every circumstance. Too adept: speculation outstripped experiment, and before long a counterreformation was inevitable. In the 1920s the very empiricist ideas that James had attacked, embodied in the notion of the blank slate, swept back to power not just in psychology (with John B. Watson and B. F. Skinner) but in anthropology (Franz Boas), psychiatry (Freud), and sociology (Durkheim). Nativism was almost totally eclipsed until 1958, when Noam Chomsky once again pinned its charter to the door of science. In a famous review of a book on language by Skinner, Chomsky argued that it was impossible for a child to learn the rules of language from examples: the child must have innate rules to which the vocabulary of the language was fitted. Even then, the blank slate continued to dominate human sciences for many years. It was not until a century after his book was published that William James’s idea of uniquely human instincts was at last taken seriously again in a new manifesto of nativism, written by John Tooby and Leda Cosmides (see ).

More of that later. First, a digression on teleology. It was Darwin’s genius to turn the old theological argument from design on its head. Until then, the obvious fact that parts of organisms appear to be engineered for a purpose—the heart for pumping, the stomach for digesting, the hand for grasping—seemed, logically, to imply a designer, just as a steam engine implied the existence of an engineer. Darwin saw how the entirely backward-looking process of natural selection—what Richard Dawkins called the blind watchmaker—could nonetheless produce purposeful design. Though in theory it makes teleological nonsense to talk of a stomach having its own purpose, since the stomach has no mind, in practice it makes perfect sense so long as you engage the grammatical equivalent of a four-wheel drive, the passive voice: stomachs have been selected to appear as if equipped with purposeful design. Since I have an aversion to the passive voice, I intend to avoid that problem throughout this book by pretending that there is indeed a teleological engineer thinking ahead and planning purposefully. The philosopher Daniel Dennett calls such an artifact a “skyhook,” since it is the rough equivalent of a civil engineer hanging his scaffolding from the sky, but for the sake of simplicity I shall call my skyhook the Genome Organizing Device, or GOD for short. This may keep religious readers happy, and it allows me to use the active voice. So the question is: how does the GOD build a brain that can express an instinct?

Back to William James. To support his assertion that human beings have more instincts than other animals, James systematically enumerated the human instincts. He began with the actions of babies: sucking, clasping, crying, sitting up, standing, walking, and climbing were all, he suggested, expressions of impulse, not imitations or associations. So, as the child grew, were emulation, anger, and sympathy. So was a fear of strangers, loud noises, heights, the dark, and reptiles. (“The ordinary cock-sure evolutionist ought to have no difficulty in explaining these terrors,” wrote James, neatly anticipating the argument of what is now called evolutionary psychology, “as relapses into the consciousness of the cave-men, a consciousness usually overlaid in us by experiences of more recent date.”) He moved on to acquisitiveness, noting the tendency of boys to collect things. He noticed the very different play preferences of boys and girls. Parental love, he suggested, was at least initially stronger in women than in men. He went quickly through sociability, shyness, secretiveness, cleanliness, modesty, and shame. “Jealousy is unquestionably instinctive,” he remarked.

The strongest of the instincts, he believed, was love. “Of all propensities, the sexual impulses bear on their face the most obvious signs of being instinctive, in the sense of blind, automatic and untaught.” But, he insisted, the fact that sexual attraction was instinctive did not mean it was irresistible. Other instincts, like shyness, prevent us acting upon every sexual attraction.

Let me take James at his word, provisionally at least, and examine the idea of the love instinct in a little more depth. If he is right, there must be some heritable factor, which gives rise to a physical or chemical change in our brains when we fall in love; that change causes, rather than being caused by, the emotion of falling in love. Such as this, from the scientist Tom Insel:

A working hypothesis is that oxytocin released during mating activates those limbic sites rich in oxytocin receptors to confer some lasting and selective reinforcement value on the mate.

Or, to put it more poetically, you fall in love.

What is this oxytocin and why does Insel make such an extravagant claim for it? The story starts with an almost ridiculously unromantic process: urination. Some 400 million years ago, when the ancestors of our species first left the water, they were equipped with a tidy little hormone called vasotocin, a miniature protein made out of a chain of just nine amino acids formed into a ring. Its job was to regulate the balance of salt and water in the body, and it performed this job by rushing about switching on cells in the kidney or other organs. Fish still use two different versions of vasotocin for this purpose today, and so do frogs. In the descendants of reptiles—and that includes human beings—there are two slightly different copies of the relevant gene lying next to each other, facing different ways (in human beings on chromosome 20). The result today is that all mammals have two such hormones, called vasopressin and oxytocin, that differ at two of the links in the chain.

These hormones still do their old job. Vasopressin tells the kidney to conserve water; oxytocin tells it to excrete salt. But, like vasotocin in modern fish, they also have a role in the regulation of reproductive physiology. Oxytocin stimulates the contraction of muscles in the womb during birth; it also causes milk to be expelled from the ducts in the breast. The GOD is an economizer: having invented a switch for one purpose, he readapts it for other purposes, by expressing the oxytocin receptor in a different organ.

An even greater surprise came in the early 1980s, when scientists suddenly realized that vasopressin and oxytocin had a job to do inside the brain as well as being secreted from the pituitary gland into the bloodstream.

So they tried injecting oxytocin and vasopressin into the brains of rats to see what the effect would be. Bizarrely, a male rat injected with intracerebral oxytocin immediately begins yawning and simultaneously gets an erection. So long as the dose is low, the rat also becomes more highly sexed: it ejaculates sooner and more frequently. In female rats, intracerebral oxytocin induces the animal to adopt a mating posture. In human beings, meanwhile, masturbation increases oxytocin levels in both sexes. All in all, oxytocin and vasopressin in the brain seem to be connected to mating behavior.

All this sounds rather unromantic: urine, masturbation, breast feeding—hardly the essence of love. Be patient. In the late 1980s, Tom Insel was working on the effect of oxytocin on maternal behavior in rats. Brain oxytocin seemed to help the mother rat form a bond with her young, and Insel identified the parts of the rat brain that were sensitive to the hormone. He switched his attention to the pair bond, wondering if there were parallels between a female’s bond to her young and the bond to her mate. At this point he met Sue Carter, who had begun to study prairie voles in the laboratory. She told him that the prairie vole is a rarity among mice for its faithful marriages. Prairie voles live in couples, and both father and mother care for the young for many weeks. Montane voles, on the other hand, are more typical of mammals: the female mates with a passing polygamist, separates quickly from him, bears young alone, and abandons them after a few weeks to fend for themselves. Even in the laboratory, this difference is clear: mated prairie voles stare into each other’s eyes and bathe the babies; mated montane voles treat their spouses like strangers.

Insel examined the brains of the two species. He found no difference in the expression of the two hormones themselves, but a big difference in the distribution of molecular receptors for them—the molecules that fire up neurons in response to the hormones. The monogamous prairie voles had far more oxytocin receptors in several parts of the brain than the polygamous montane voles. Moreover, by injecting oxytocin or vasopressin into the brains of prairie voles, Insel and his colleagues could elicit all the characteristic symptoms of monogamy, such as a strong preference for one partner and aggression toward other voles. The same injections had little effect on montane voles, and the injection of chemicals that block the oxytocin receptors prevented the monogamous behavior. The conclusion was clear: prairie voles are monogamous because they respond more to oxytocin and vasopressin.

In a virtuoso display of scientific ingenuity, Insel’s team has gone on to dissect this effect in convincing detail. They knock the oxytocin gene out of a mouse before birth. This leads to social amnesia: the mouse can remember some things, but it has no memory of mice it has already met and will not recognize them. Lacking oxytocin in its brain, a mouse cannot recognize mice it met 10 minutes before—unless those mice were “badged” with a nonsocial cue such as a distinctive lemon or almond scent (Insel compares this situation to that of an absent-minded professor at a conference who recognizes friends by their name tags, not their faces). Then by injecting the hormone into just one part of the animal’s brain—the medial amygdala—in later life the scientists can restore social memory to the mouse completely.

In another experiment, using a specially adapted virus, they turn up the expression of the vasopressin receptor gene in the ventral pallidum, a part of a vole’s brain important for reward. (Pause here to roll that idea around your mind a few times to appreciate just what science can do these days: scientists use viruses to turn up the volumes of genes in one part of the brain of a rodent. Even 10 years ago such an experiment was unimaginable.) The result of turning up the gene’s expression is to “facilitate partner preference formation,” which is geekspeak for “make them fall in love.” They conclude that for a male vole to pair-bond, it must have both vasopressin and vasopressin receptors in its ventral pallidum. Since mating causes a release of oxytocin and vasopressin, the prairie vole will pair-bond with whatever animal it has just mated with; the oxytocin helps in memory, the vasopressin in reward. The montane vole, by contrast, will not react in the same way, because it lacks receptors in that area. Female montane voles express these receptors only after giving birth, so they can be nice to their babies, briefly.

So far I have talked of oxytocin and vasopressin as if they were the same thing, and they are so similar that they probably stimulate each other’s receptors somewhat. But it appears that to the extent that they do differ, oxytocin makes female voles choose a partner; vasopressin makes males choose a partner. When vasopressin is injected into the brain of a male prairie vole, he becomes aggressive toward all voles except his mate. Attacking other voles is a (rather male) way of expressing love.

All this is astonishing enough, but perhaps the most exciting result to emerge from Insel’s laboratory concerns the genes for the receptors. Remember that the difference between the prairie vole and the montane vole lies not in the expression of the hormone but in the pattern of expression of the hormone’s receptors. These receptors are themselves products of genes. The receptor genes are essentially identical in the two species, but the promoter regions, upstream of the genes, are very different. Now recall the lesson of : that the difference between closely related species lies not in the text of genes themselves but in their promoters. In the prairie vole, there is an extra chunk of DNA text, on average about 460 letters long, in the middle of the promoter. Insel’s team made a transgenic mouse with this expanded promoter, and it grew up with a brain like a prairie vole’s, expressing vasopressin receptors in all the same places, though it did not form a pair bond. Steven Phelps then caught 43 wild prairie voles in Indiana and sequenced their promoters: some had longer insertions than others. The insertions varied from 350 to 550 letters in length. Are the long ones in more faithful husbands than the short ones? Not yet known.

The conclusion to which Insel’s work is leading is devastating in its simplicity. The ability of a rodent to form a long-term attachment to its sexual partner may depend on the length of a piece of DNA text in the promoter switch at the front of a certain receptor gene. That in turn decides precisely which parts of the brain will express the gene. Of course, like all good science, this discovery raises more questions than it settles. Why should feeding oxytocin receptors in that part of the brain make the mouse feel well-disposed toward its partner? It is possible that the receptors induce a state a bit like addiction, and in this respect it is noticeable that they seem to link with the D2 dopamine receptors, which are closely involved in various kinds of drug addiction. On the other hand, without oxytocin, mice cannot form social memories, so perhaps they simply keep forgetting what their spouse looks like.

Mice are not men. You know by now that I am about to start extrapolating anthropomorphically from pair-bonding in voles to love in people, and you probably do not like my drift. It sounds reductionist and simplistic. Romantic love, you say, is a cultural phenomenon, overlaid with centuries of tradition and teaching. It was invented at the court of Eleanor of Aquitaine, or some such place, by a bunch of oversexed poets called troubadours; before that there was just sex.

Even though in 1992 William Jankowiak surveyed 168 different ethnographic cultures and found none that did not recognize romantic love, you may be right. I certainly cannot prove to you—yet—that people fall in love when their oxytocin and vasopressin receptors get tingled in the right places in their brains. Yet. And there are cautionary hints about the dangers of extrapolating from one species to another: sheep seem to need oxytocin to form maternal attachment to their young; mice apparently do not. Human brains are undoubtedly more complicated than mouse brains.

But I can draw your attention to some curious coincidences. A mouse shares much of its genetic code with a human being. Oxytocin and vasopressin are identical in the two species and are produced in the equivalent parts of the brain. Sex causes them to be produced in the brain in both human beings and rodents. Receptors for the two hormones are virtually identical and are expressed in equivalent parts of the brain. Like those of the prairie vole, the human receptor genes (on chromosome 3) have a—smaller—insertion in their promoter regions. As with the prairie voles of Indiana, the lengths of those promoter insertions vary from individual to individual: in the first 150 people examined, Insel found 17 different lengths. And when a person who says she (or he) is in love contemplates a picture of her loved one while sitting in a brain scanner, certain parts of her brain light up that do not light up when she looks at a picture of a mere acquaintance. Those brain parts overlap with the ones stimulated by cocaine. All this could be a complete coincidence, and human love may be entirely different from rodent pair bonding, but given how conservative the GOD is and how much continuity there is between human beings and other animals, you would be unwise to bet on it.

Shakespeare was ahead of us, as usual. In A Midsummer Night’s Dream, Oberon tells Puck how Cupid’s arrow fell upon a white flower (the pansy), turning it purple, and that now the juice of this flower

… on sleeping eyelids laid
Will make or man or woman madly dote
Upon the next live creature that it sees.

Puck duly fetches a pansy, and Oberon wreaks havoc with the lives of those sleeping in the forest, causing Lysander to fall in love with Helena, whom he has previously scorned; and causing Titania to fall in love with Bottom the weaver wearing the head of an ass.

Who would now wager against me that I could not soon do something like this to a modern Titania? Admittedly, a drop on the eyelids would not suffice. I would have to give her a general anesthetic while I cannulated her medial amygdala and injected oxytocin into it. I doubt even then that I could make her love a donkey. But I might stand a fair chance of making her feel attracted to the first man she sees upon waking. Would you bet against me? (I hasten to add that ethics committees will—or should—prevent anybody taking up my challenge.)

I am assuming that, unlike most mammals, human beings are basically monogamous like prairie voles, and not promiscuous like montane voles. I base this assumption on the argument enunciated in concerning the size of testicles; on the ample evidence from ethnography that, though most human societies allow polygamy, most human societies are still dominated by monogamous relationships; and on the fact that human beings usually practice some paternal care—a characteristic feature of the few mammal species that live as social monogamists. Furthermore, as we have liberated human life from economic and cultural straitjackets, such as arranged marriage, we have found monogamy growing more dominant, not less. In 1998 the most powerful man in the world, far from treating himself to a gigantic harem, got into trouble for having an affair with one intern. The evidence is all around you for long-term and exclusive (but sometimes cheated-on) pair bonds as the commonest pattern in human relationships.

Chimpanzees are different. Long-term pair bonds are unknown among them, and I predict that they have fewer oxytocin receptors in the relevant parts of their brains than human beings, probably as a result of having shorter gene promoters.

The story of oxytocin lends at least tentative support to William James’s notion that love is an instinct, evolved by natural selection, and is part of our mammal heritage, just like four limbs and 10 fingers. Blindly, automatically, and untaught, we bond with whoever is standing nearest when the oxytocin receptors in the medial amygdala get tingled. One sure way to tingle them is to have sex, although presumably chaste attraction can also do the trick. Is this why breaking up is hard to do?

Having oxytocin receptors does not make it inevitable that somebody will fall in love during his life, nor predictable when it will happen, or with whom. As Niko Tinbergen, the great Dutch ethologist, demonstrated in his studies of instincts, the expression of a fixed, innate instinct must often be triggered by an external stimulus. One of Tinbergen’s favorite species was the stickleback, a tiny fish. Male sticklebacks become red on the belly in the breeding season, when they defend small territories in which they build nests, which attract females. Tinbergen made little models of fish and caused them to “invade” the territory of a male fish. A model of a female elicited the courtship dance of the male, even if the model was astonishingly crude; so long as it had a “pregnant” belly, it excited the male. But if the model had a red belly, it would trigger an attack. It could be just an oval blob with a crudely drawn eye but no fins or tail: still it was attacked just as vigorously as if it were a real male rival—so long as it was red. One of the legends of Leiden, where Tinbergen first worked, is that he noticed his sticklebacks would threaten the red post-office vans that drove past the window.

Tinbergen went on to demonstrate the power of these “innate releasing mechanisms” to provoke the expression of an instinct in other species, notably the herring gull. Herring gulls have a yellow beak with a bright red spot near the tip. The chicks peck at this spot when begging for food. By presenting newborn chicks with a series of models, Tinbergen demonstrated that the spot was a powerful releaser for the begging action, and the redder it was the more powerful it was. The color of the beak or the head of the bird mattered not at all. So long as there was a contrasting spot near the tip of the bill, preferably in red, it would elicit pecking. In modern jargon, scientists would say that the chick’s instinct and the adult’s beak spot had “coevolved.” An instinct is designed to be triggered by an external object or event. Nature plus nurture.

The significance of Tinbergen’s experiments was that they revealed just how complex instincts could be, and yet how simply triggered. The digger wasp Tinbergen studied would dig a burrow, go and catch a caterpillar, paralyze it with a sting, bring it back to the burrow, and deposit it with an egg on top, so that the baby wasp could feed on the caterpillar while growing. All this complex behavior, including the ability to navigate back to the burrow, was achieved with almost no learning, let alone parental teaching. A digger wasp never meets its parents. A cuckoo migrates to Africa and back, sings its song, and mates with one of its own species without, as a chick having ever seen either a parent or a sibling.

The notion that animal behavior is in the genes once troubled biologists as much as it now troubles social scientists. Max Delbruck, a pioneering molecular biologist, refused to believe that his colleague at Caltech Seymour Benzer had found a behavioral mutant fly. Behavior, Delbruck insisted, was too complex to reduce to single genes. Yet the idea of behavior genes has long been accepted by amateur breeders of domestic animals. The Chinese started breeding mice of different colors in the seventeenth century or earlier, and they produced a mouse called the waltzing mouse, famous for its dancelike gait caused by an inherited defect in the inner ear. Mouse breeding then caught on in Japan in the nineteenth century and thence spread to Europe and America. Sometime before the year 1900 a retired schoolteacher in Granby, Massachusetts, by the name of Abbie, took up the “mouse fancying” hobby. Soon she was breeding different strains of mice herself in a small barn adjoining her property and selling them to pet shops. She was especially fond of what were by then known as Japanese waltzing mice, and she developed several new strains. She also noticed that some strains got cancer more often than others; this hint was picked up by Yale University and became the basis of early studies of cancer.

But it was Lathrop’s link to Harvard that uncovered the link between genes and behavior. William Castle of Harvard bought some of her mice and started a mouse laboratory. Under Castle’s student Clarence Little the main mouse laboratory moved to Bar Harbor, Maine, where it still is—a giant factory of inbred mouse strains used in research. Very early on, the scientists began to realize that different strains of mice behaved in different ways. Benson Ginsburg, for instance, found out the hard way. He noticed that when he picked up a mouse of the “guinea-pig” strain (named for the color of its coat), he often got bitten. He was soon able to breed a new strain that had the coat color but not the aggressive streak: proof enough that aggression was somewhere in the genes. His colleague Paul Scott also developed aggressive strains of mice; but, bizarrely, Ginsburg’s most aggressive strain was Scott’s most pacific. The explanation was that Scott and Ginsburg had handled the mice differently as babies. For some strains, handling did not matter. But for one strain in particular, C57-Black-6, early handling increased the aggressiveness of the mouse. Here was the first hint that a gene must interact with an environment if it is to have its effect. Or, as Ginsburg said, the road from the “encoded genotype” the mouse inherits to the “effective genotype” it expresses passes through the process of social development.

Ginsburg and Scott both later went on to work with dogs, Scott proving by crossing experiments between cocker spaniels and African basenjis that play-fighting in puppies is controlled by two genes which regulate the threshold for aggression. But science has not needed to prove the inheritance of behavior in dogs: that was old news to dog breeders. The point of dogs is that they come in different behavioral types: retrievers, pointers, setters, shepherds, terriers, poodles, bulldogs, wolfhounds—their very names denote the fact that they have instincts bred into them. And those instincts are innate. A retriever cannot be trained to guard livestock, and a guard dog cannot be trained to herd sheep. It’s been tried. In the process of domestication, dogs have kept incomplete or exaggerated elements of wolf behavior development. A wolf will stalk, chase, pounce, grab, kill, dissect, and carry food, and a wolf pup will practice each of these activities in turn as it grows up. Dogs are wolf pups frozen in the practicing stage. Collies and pointers are stuck in the stalking stage; retrievers are stuck with carrying and pit bulls with biting: each is a frozen mixture of different themes seen in wolf pups. Is it in their genes? Yes: “Breed-specific behaviors are irrefutable,” says the dog chronicler Stephen Budiansky.

Or ask the cattle-breeders. I have in front of me a catalog of dairy bulls designed to entice me into ordering some semen by mail. In enormous detail it describes the quality and shape of the bull’s udder and teats, its milk-producing ability, its milking speed and even its temperament. But surely, you point out, bulls don’t have udders? On every page there is a picture of a cow, not a bull. What the catalog is referring to is not the bull himself but his daughters. “Zidane, the Italian No 1,” it boasts, “improves frame traits and fixes on tremendous rumps with ideal slope. He is particularly impressive in his feet and leg composites with excellent set and terrific depth of heel. He leaves faultless udders, which are snugly attached with deep clefts.” The characteristics are all female, but the attribution is to the sire. Perhaps I would prefer to buy a straw of semen from Terminator, whose daughters have “great teat placement,” or Igniter, a bull that is a “milking speed specialist” whose daughters “display great dairy character.” I might wish to avoid Moet Flirt Freeman, because although his daughters have “tremendous width across the chest” and give more milk than their mothers, the small print admits that they are also slightly “below average” in temperament—which probably means that they tend to kick out when being milked. They are also slow milkers.

The point is that cattle-breeders have no qualms about attributing behavior to genes, just as they attribute anatomy to genes. Minute differences in the behavior of cows they confidently ascribe to the semen that arrived through the mail. Human beings are not cows. Admitting instinct in cows does not prove that human beings are also ruled by instinct, of course. But this admission does demolish the assumption that because behavior is complex or subtle, it cannot be instinctive. Such a comforting illusion is still widespread within the social sciences, yet no zoologist who has studied animal behavior could believe that complex behavior cannot be innate.

MARTIANS AND VENUSIANS

Defining “instinct” has baffled so many scientists that some refuse to use the word at all. An instinct need not be present from birth: some instincts develop only in adult animals (as wisdom teeth do). An instinct need not be inflexible: digger wasps will alter their behavior according to how many caterpillars they find already in the burrow they are provisioning. An instinct need not be automatic: unless it meets a red-bellied fish, the stickleback male will not fight. And the boundaries between instinctive and learned behavior are blurred.

But imprecision does not necessarily render a word useless. The boundaries of Europe are uncertain—How far east does it stretch? Are Turkey and Ukraine in it?—and there are many different meanings of the word “European,” but it is still a useful word. The word “learn” covers a multitude of virtues, but it is still a useful word. Likewise, I believe that to call behavior instinctive can still be useful. It implies that the behavior is at least partially inherited, hardwired, and automatic, given the expected environment. A characteristic feature of an instinct is that it is universal. That is, if something is primarily instinctive in human beings, then it must be approximately the same in all people. Anthropologists have always been torn between an interest in human similarities and an interest in human differences, with the advocates of nature emphasizing the former and the advocates of nurture stressing the latter. The fact that people smile, frown, grimace, and laugh in much the same way all over the world struck Darwin, and would later strike the ethologists Irenaeus Eibl-Eibesfeldt and Paul Ekman, as astonishing. Even among those inhabitants of New Guinea and the Amazon till then uncontacted by “civilization,” these emotional expressions have the same form and the same meaning. At the same time, the astonishing variety of rituals and habits expressed by the human race testifies to its capacity for difference. As usual in science, each side of the argument pushed the other to extreme positions.

Perhaps it would satisfy both (or neither) to focus on the paradox of human differences that are universally similar all over the world. After all, similarity is the shadow of difference. The prime candidate is sex and gender difference. Nobody now denies that men and women are different not just in anatomy but also in behavior. From best-selling books about men and women being from different planets to the increasing polarization of films into those that appeal to men (action) or to women (relationships), it is surely no longer controversial to assert that—despite exceptions—there are consistent mental as well as physical differences between the sexes. As the comedian Dave Barry puts it, “If a woman has to choose between catching a fly ball and saving an infant’s life, she will choose to save the infant’s life without even considering if there are men on base.” Are such differences nature, nurture, or both?

Of all the sex differences, the best-studied are the ones to do with mating. In the 1930s, psychologists first started asking men and women what they sought in a mate, and they have been asking them ever since. The answer seems so obvious that only a laboratory nerd or a Martian would bother to ask the question. But sometimes the most obvious things are the ones that most need demonstrating.

They found many similarities: both sexes wanted intelligent, dependable, cooperative, trustworthy, and loyal partners. But they also found differences. Women rated good financial prospects in their partners twice as highly as men. Hardly surprising, since men were breadwinners in the 1930s. Come back in the 1980s and you would surely find such a patently cultural difference vanishing. No: in every survey conducted since then, right up to the present day, the same preference emerges just as strongly. To this day, American women rate financial prospects twice as highly as men do when seeking mates. In personal advertisements, women mention wealth as a desirable feature of a partner 11 times as often as men do. The psychology establishment dismissed this result: it merely reflected the importance of money in American culture, not a universal sex difference. So the psychologist David Buss went and asked foreigners, and he got the same answer from Dutch and German men and women. Don’t be absurd, he was told; western Europeans are just like Americans. So Buss asked 10,047 people from 37 different cultures on six continents and five islands, ranging from Alaska to Zululand. In every culture, bar none, women rated financial prospects more highly than men. The difference was highest in Japan and lowest in Holland but it was always there.

This was not the only difference he found. In all 37 cultures, women wanted men older than themselves. In nearly all cultures, social status, ambition, and industriousness in a mate mattered more to women than to men. Men by contrast placed more emphasis on youth (in all cultures men wanted younger women) and physical appearance (in all cultures, men wanted beautiful women more than women wanted beautiful men). In most cultures men also placed slightly more emphasis on chastity and fidelity in their partners, while (of course) being much more likely to seek extramarital sex themselves.

Well, what a surprise! Men like pretty, young, faithful women, while women like rich, ambitious, older men. A casual glance through films, novels, or newspapers could have revealed this to Buss, or to any passing Martian. Yet the fact remains that many psychologists had firmly told Buss he would not be able to find such trends repeated outside the countries of the west, let alone all over the world. Buss proved something which was—at least to the social science establishment—very surprising.

Many social scientists argue that the reason women seek wealthy men is that men have most of the wealth. But once you know that this is universal in the human race, you can easily turn it around. Men seek wealth because they know it attracts women—just as women pay more attention to appearing youthful because they know it attracts men. This direction of causality was never less plausible than the other, and given the evidence of universality, it is now more plausible. Aristotle Onassis, who knew a bit about both money and beautiful women, reputedly once said: “If women did not exist, all the money in the world would have no meaning.”

By proving how universal so many sex differences in mating preferences are, Buss has thrown the burden of proof onto those who would see a cultural habit rather than an instinct. But the two explanations are not mutually exclusive. They are probably both true. Men seek wealth to attract women; therefore women seek wealth because men have it; therefore men seek wealth to attract women; and so on. If men have an instinct to seek the baubles that lead to success with women, then they are likely to learn that within their culture money is one such bauble. Nurture is reinforcing nature, not opposing it.

With the human species, as Dan Dennett observed, you can never be sure that what you see is instinct, because you might be looking at the result of a reasoned argument, a copied ritual, or a learned lesson. But the same applies in reverse. When you see a man chasing a woman just because she is pretty, or a girl playing with a doll while her brother plays with a sword, you can never be sure that what you are seeing is just cultural, because it might have an element of instinct. Polarizing the issue is entirely mistaken. It is not a zero-sum game, where culture displaces instinct or vice versa. There might be all sorts of cultural aspects to a behavior that is grounded in instinct. Culture will often reflect human nature rather than affect it.

MONEY OR DIAMOND?

Buss’s study of global similarity in difference proves the universality of different approaches to mating behavior but says nothing about how they come about. Suppose he is right and the differences are evolved, adaptive, and therefore at least partly innate. How do they develop and under what influences? Thanks to “Money versus Diamond,” an extraordinary battle in the nature–nurture war, there is now a glimmer of light being cast upon this subject.

Money is John Money, a psychologist from New Zealand who reacted against his strict religious upbringing to become an outspoken “missionary” of sexual liberation at Johns Hopkins University in Baltimore, eventually defending not just free love but even consenting pedophilia. Diamond is Mickey Diamond, a tall, soft-spoken, bearded son of Ukrainian Jewish immigrants to the Bronx who moved first to Kansas and then to Honolulu, where he studies the factors determining sexual behavior in animals and people.

Money believes that sex roles are the products of early experience, not instinct. In 1955 he set out his theory of psychosexual neutrality based on the study of 131 human “hermaphrodites”—people who had been born with ambiguous genitalia. At birth, said Money, human beings are psychosexually neutral. Only after experience, at about the age of two, do they develop “gender identity.” “Sexual behavior and orientation as male or female does not have an innate, instinctive basis,” he wrote. “It becomes differentiated as masculine or feminine in the course of the various experiences of growing up.” Therefore, said Money, a human baby can be literally assigned to either sex, a belief that was used by doctors to justify surgery to change baby boys born with abnormal penises into girls. Such surgery became standard practice: males with unusually tiny penises were “reassigned” as females.

In contrast, the group in Kansas came to the conclusion that “the biggest sex organ is between the ears, not between the legs” and began to challenge the orthodoxy that sex roles were environmentally determined. In 1965 Diamond argued the point in a paper critical of Money, charging that Money had presented no case histories to support his theory of psychosexual neutrality, that the evidence from hermaphrodites was irrelevant—if their genitalia were ambiguous, their brains might be, too—and that it was more plausible that human beings, like guinea pigs, experienced a prenatal fixation of mental sex identity. In effect he challenged Money to produce a psychosexually neutral, normal child, or one who had accepted sex reassignment.

Money brushed aside the criticism as he gathered the rewards of increasing fame. His paper had won a prize; that had led to a huge grant; and when his team began transsexual surgery, he became a celebrity profiled in newspapers and on television. But Diamond had hit a nerve, for the very next year Money took on a case of a normal boy who had lost his penis after a botched circumcision. The boy was a monozygotic twin, so the opportunity to demonstrate how he could be turned into a woman, while his twin developed as a man, was irresistible. On Money’s advice the boy was surgically reassigned as a girl then raised by his parents as a girl and never told of her origin. In 1972 Money published a book describing the case as an unqualified success. It was hailed in the press as definitive proof that sex roles were a product of society, not biology; it influenced a generation of feminists at a critical time; it entered the psychology textbooks; and it influenced many doctors who now saw sex reassignment as a simple solution to a complicated problem.

Money seemed to have won the argument. Then in 1979 a BBC television began investigating the case. The team had heard rumors that the boy who became a girl was not the success Money claimed. They managed to penetrate the anonymity of the case and even briefly meet the girl in question, though they did not divulge her identity on air. Called Brenda Reimer, she lived with her family in Winnipeg and was then 14. What the team saw was an unhappy youth with masculine body language and a deep voice. The BBC crew interviewed Money, who reacted with fury at the invasion of the family’s privacy. Diamond continued to press Money for details but got nowhere. Money now dropped all reference to the case from his published work. The trail once more went cold. Then in 1991, in print, Money blamed Diamond for inciting the BBC to invade the girl’s privacy. Enraged, Diamond began trying to contact psychiatrists who might have treated the case. In 1995, at last, he met “Brenda Reimer.”

Except Brenda was now called David and was a happily married man with adopted children. He had endured a confused and unhappy childhood, constantly rebelling against girlish things, though he knew nothing of having been born a boy. When at 14 he still insisted on living as a boy, his parents at last told him of his past. He immediately demanded surgery to restore a penis and adopted the life of a teenage male. Diamond persuaded David to let him tell the story to the world (using a pseudonym) so that others might not have to endure the same fate in the future. In 2000, the writer John Colapinto convinced David to drop his anonymity altogether for a book.

Money has never apologized either to the world for misleading people about the success of the reassignment, or to David Reimer. Today Diamond wonders what would have happened if the little boy had been a gay or transsexual who might have wanted to live either in an effeminate way or as a female, or had not been willing to come out of his closet and tell his story.

David Reimer is not alone. Most boys reassigned as girls declare themselves boys at adolescence. And a recent study of people born with ambiguous genitalia found that those who escaped the surgeon’s knife had fewer psychological problems than those who had been operated on in childhood. The large majority of those males who were switched to live as girls have reverted, on their own, to live as males.

Gender roles are at least partly automatic, blind, and untaught, to use William James’s terms. Hormones within the womb trigger masculinization, but those hormones originate within the body of the baby and are themselves triggered by a series of events that begin with the expression of a single gene on the Y chromosome. (There are plenty of species that allow the environment to determine gender. In crocodiles and turtles, for example, the sex of the animal is set by the temperature at which the egg is incubated. But there are genes involved in such a process, too. Temperature triggers the expression of sex-determining genes. The prime cause may be environmental, but the mechanism is genetic. Genes can be consequence as well as cause.)

FOLK PSYCHOLOGY

Boys like David Reimer want to be boys. They like toys, weapons, competition, and action better than dolls, romance, relationships, and families. They do not come into the world with all these preferences fully formed, of course, but they do come with some ineffable preference to identify with boyish things. This is what the child psychologist Sandra Scarr has called “niche picking”: the tendency to pick the nurture that suits your nature. The frustrations of David Reimer’s youth were caused by his not being allowed to pick his niche.

In this sense, cause and effect are probably circular. People both like doing what they find they are good at and are good at what they like doing. This implies that the sex difference is at least jump-started by instinct, by innate behavioral differences that predate experience. Like many parents who have had children of both sexes, I found the differences surprisingly strong and early. I also had no difficulty in believing that I and my wife were reacting to, rather than causing, such gender dissimilarities. We bought trucks for the boy and dolls for the girl not because we wanted them to be different, but because it was painfully obvious that one wanted trucks and the other dolls.

Exactly how early do these differences emerge? Svetlana Lutchmaya, a student of Simon Baron-Cohen’s at Cambridge, filmed 29 girls and 41 boys at 12 months old and analyzed how often the baby looked at the mother’s face. As expected, the girls made far more eye contact than the boys. Lutchmaya then went back and measured the testosterone levels present in the womb during the first trimester of each baby’s gestation. This was possible because in every case the mother had had amniocentesis and a sample of amniotic fluid had been stored. She found that the fetal testosterone level was generally higher for the boys than the girls, and that among the boys there was a significant correlation: the higher the testosterone level, the less eye contact the baby made as a one-year-old.

Baron-Cohen then asked another student, Jennifer Connellan, to go back even further, to the first day of life. She gave 102 24-hour-old babies two things to look at: her own face, or a physical-mechanical mobile of approximately the same size and shape as a face. The baby boys slightly preferred to look at the mobile; the baby girls slightly preferred the face.

So females’ relative preference for faces, which gradually turns into a preference for social relationships, seems to be there in some form from the start. This distinction between the social and physical world may be a crucial clue to how human brains work. The nineteenth-century psychologist Franz Brentano divided the universe rather starkly into two kinds of entities: those that have intentionality and those that do not. The former can move themselves spontaneously and can have goals and wants; the latter obey only physical laws. This is a distinction that fails at the edges—what about plants?—but as a rule of thumb it works rather well. Evolutionary psychologists have begun to suspect that human beings instinctively apply two different mental processes to understanding such objects: what Daniel Dennett has called folk psychology and folk physics. We assume that a footballer moved because he “wanted to” move but that a football moved only because it was kicked. Even babies express surprise when objects appear to disobey the laws of physics—if objects move through each other, if large objects seem to go into smaller ones, or if objects move without being touched.

You can see where I am heading, I suspect: on average, men are more interested in folk physics than women, who are more interested in folk psychology than men. Simon Baron-Cohen’s research focuses on autism, a difficulty with the social world that affects mainly boys. Together with Alan Leslie, Baron-Cohen pioneered the theory that autistic boys have trouble theorizing about the minds of others, though he now prefers to use the term “empathizing.” Severe autism has many other features, including difficulty with language; but in what is probably its “purer” and less severe form, Asperger’s syndrome, autism seems mainly to consist of a difficulty in empathizing with other people’s thoughts. Since boys are less good at empathizing than girls anyway, perhaps autism is just an extreme version of the male brain. Hence Baron-Cohen’s interest in the inverse correlation between prenatal testosterone and eye contact: the masculinization of the brain by testosterone may go “too far” in autistics.

Intriguingly, children with Asperger’s syndrome are often better than normal at folk physics. Not only are they frequently fascinated by mechanical things, from light switches to airplanes, but they generally take an engineering approach to the world, trying to understand the rules by which things—and people—operate. They frequently become precociously expert in factual knowledge and mathematics. They are also more than twice as likely as other children to have fathers and grandfathers who worked in engineering. On a standard test of autistic tendencies, scientists generally score higher than nonscientists and physicists and engineers score higher than biologists. Baron-Cohen says of one brilliant mathematician, a winner of the Fields medal, who has Asperger’s syndrome: “Empathy passes him by.”

To demonstrate how a difficulty with folk psychology can coexist happily with expertise at folk physics, psychologists designed two remarkably similar tests called the false-belief test and the false-photo test. In the false-belief test, a child sees an experimenter move a concealed object from one receptacle to another while a third person is not watching. The child then has to say where the third person will look for the object. To get the right answer, the child has to understand that the third person holds a false belief. All children pass this test for the first time around the age of four (boys later than girls), but autistics are especially late developers.

In the false-photo test, by contrast, the child takes a Polaroid photograph of a scene, then, while the picture is developing, sees the experimenter move one of the objects in the scene. The child is asked which position the object will occupy in the photograph. Autistics have no difficulty with this test, because their understanding of folk physics outstrips their understanding of folk psychology.

Folk physics is just part of a skill that Baron-Cohen calls “systemizing.” It is the ability to analyze input–output relationships in the natural, technical, abstract, and even human world: to understand cause and effect, regularity and rules. He believes that human beings have two separate mental abilities, systemizing and empathizing, and that though some people are good at both, others are good at one and bad at the other. Those who are good systemizers and bad empathizers will try to use their systemizing skills to solve social problems. For instance, one person with Asperger’s syndrome said to Baron-Cohen that “Where do you live?” was not a good question, since it could be answered on many levels: country, city, district, street, or house number. True, but most people solve the problem by empathizing with the questioner. If speaking to a neighbor, they might name the house; if to a foreigner, the country.

If Asperger’s people are good systemizers and bad empathizers, with extreme-male brains, the thought arises that there are probably people who are good empathizers and poor systemizers, with extreme female brains. A moment’s thought will confirm that we all know such people, but their particular combination of skills is rarely classified as pathological. It is probably easier to live a normal life in the modern world with poor systemizing skills than with poor empathizing skills. In the Stone Age, it might have been less easy.

A MIND IN PARTS

The discussion of empathy illustrates a very William Jamesian theme—separate instincts. To be good at empathizing you need a domain, or module, in your mind that learns to treat animate creatures intuitively as having mental states as well as physical properties. To be good at systemizing, you need a domain that learns how to intuit cause and effect, regularities and rules. These are separate mental modules, separate skills, and separate learning tasks.

The empathy domain seems to rely on circuits around the paracingulate sulcus, a valley of the brain close to the midline and near the front of the head. In the studies by Chris and Uta Frith in London, this area lights up (in a suitable scanner) when a person reads a story that requires “mentalizing”—imagining the mental states of others; it does not light up when the person reads a story about physical cause and effect or a series of unlinked sentences. In people with Asperger’s syndrome, however, this area does not light up when they read stories about mental states; but a neighboring area lights up instead. This is an area involved in general reasoning, which supports the psychologists’ hunch that people with Asperger’s syndrome reason rather than empathize about social issues.

All this tends to support the idea that Jamesian instincts must be manifest in mental circuits called modules, each specifically designed to be good at its specific mental task. Such a modular view of the mind was first enunciated by the philosopher Jerry Fodor in the early 1980s and later developed by the anthropologist John Tooby and the psychologist Leda Cosmides in the 1990s. Tooby and Cosmides were attacking the then widespread belief that the brain is a general-purpose learning device. Instead, Tooby and Cosmides held that the mind is like a Swiss army knife. For blades and screwdrivers and things for helping Boy Scouts get stones out of horses’ hoofs, read vision modules, language modules, and empathy modules. Like the tools attached to the knife, these modules are rich in teleological purpose: it makes sense not just to describe what they are made of and how they do their job but what they are for. Just as the stomach is for digestion, so the visual system of the brain is for seeing. Both are functional, and functional design implies evolution by natural selection, which implies at least partly a genetic ontology. The mind therefore consists of a collection of content-specific information-processing modules adapted to past environments. Nativism was back.

This was the high point of what is sometimes called the cognitive revolution. Though it now owes much to the tragic genius Alan Turing, with his extraordinary mathematical proof that reasoning could take a mechanical form—that it was a form of computation—the cognitive revolution really began with Noam Chomsky in the 1950s. Chomsky argued that the universal features of human language, invariant throughout the world, plus the logical impossibility of a child deducing the rules of a language as quickly as it does merely from the scanty examples available to it, must imply that there was something innate about language. Much later Steven Pinker dissected the human “language instinct,” showed it had all the hallmarks of a Swiss army knife blade—structure designed for function—and added the notion that what the mind was equipped with was not innate data but innate ways of processing data.

Do not mistake this for an empty or obvious claim. It would be quite possible to imagine that vision, language, and empathy are done by different parts of the brain in different people. This indeed is the prediction that follows logically from the empiricist argument running from Locke, Hume, and Mill right up to the modern “connectionists” who design multipurpose computer networks to mimic brains. And it is wrong. Neurologists can produce battalions of case histories to support the idea that particular parts of the mind correspond to particular parts of the brain with very little variation all over the world. If you damage one part of your brain, in an accident or after a stroke, you do not suffer some generalized debility: you lose one particular feature of your mind—and the feature you lose depends precisely on which part of the brain is lost. This must imply that different parts of the brain are predesigned for different jobs, something that could come about only through genes. Genes are often thought of as constraints on the adaptability of human behavior. The reverse is true. They do not constrain; they enable.

True, there have been rear-guard actions by the retreating empiricists, but these skirmishes have delayed the advance of the modular mind only briefly. There is a degree of plasticity in the brain that allows different areas to compensate for the failure of a neighboring area. Mriganka Sur has partly rewired the eyes of a ferret to the auditory cortex of its brain rather than the visual cortex, and in some rudimentary way it can still “see,” though not very well. Although you might think it remarkable that the ferret can see at all after such surgery, there is disagreement over whether Sur’s experiment reveals more about the plasticity of the brain or the limits of that plasticity.

If the modular mind is real, then all you have to do to understand the special features of the human mind is dissect the brain to find out which bits have “hypertrophied” in the past few million years—which modules and therefore which instincts are disproportionately big. Then you will know what makes human beings special. If only it were so easy! Almost everything in the human brain is bigger than its counterpart in the chimpanzee brain. Human beings apparently do more seeing, more feeling, more moving, more balancing, more remembering, and even more smelling than chimps. If you look inside the human skull, far from finding a normal chimpanzee brain with a huge turbocharged thinking-and-speaking device attached to it, you find more of everything. Closer inspection reveals that there are certain subtle disproportions. In primates generally, compared with rodents, the bits that do smelling have shrunk dramatically and the bits that do seeing have grown. The neocortex has grown at the expense of the rest. But even here the disproportion is not very marked. Indeed, since the neocortex develops last, and the frontal regions last of all, you could simply explain the big human brain as a chimp brain that has been grown for a longer time. In its extreme form this theory holds that the brain expanded not because expansion was demanded by the requirement for it to do new functions—specifically language or culture—but because something required the enlargement of the brain stem itself and a bigger cortex came along for the ride as a passenger. Remember the lesson of the IQ domains in the ASPM gene: it is genetically easy just to make every part of the brain bigger. Once the big brain was there, presto, 50,000 years ago, Homo sapiens suddenly discovered he could use it to make bows and arrows, paint cave walls, and think about the meaning of life.

This idea has the advantage of again taking the species down a Cartesian peg—away goes the reassuring notion that humankind was the subject, rather than the object, in its own evolutionary story. But the idea is not necessarily incompatible with the idea of a modular mind. In fact, you could just as easily turn the logic on its head and argue that human beings were under selective pressure to develop more processing power in the parts of the brain needed for one function—language, say—and the easiest way for the genome to respond was to build a bigger brain generally. The ability to do more seeing and have a greater repertoire of moves was thrown in free. Besides, even a language module is hardly likely to be isolated from other functions. It needs fine discrimination of hearing; finer control of movement in the tongue, lips, and chest; greater memory, and so on.

Scientific theories, however, like empires, are at their most vulnerable when they have vanquished their rivals. No sooner had the modular mind triumphed than one of its main champions started dismantling it. In 2001 Jerry Fodor published a remarkable little book, The Mind Doesn’t Work That Way, in which he argued that though breaking down the mind into separate computational modules was by far the best theory around, it did not and could not explain how the mind works. Pointing out the “scandalous” failure of engineers to build robots capable of routine tasks like cooking breakfast, Fodor gently reminded his colleagues how little had yet been discovered and chided Pinker for his cheerful optimism that the mind had been explained. Minds, said Fodor, are capable of abducting global inferences from the information supplied by the parts of the brain. You may see, feel and hear raindrops with three different brain modules linked to different senses, but somewhere in your brain resides the inference “It is raining.” In some inevitable sense, then, thinking is a general activity that integrates vision, language, empathy, and other modules: mechanisms that operate as modules presuppose mechanisms that don’t. And almost nothing is known about the mechanisms that are not modular. Fodor’s conclusion was to remind scientists just how much ignorance they had discovered; they had merely thrown some light on how much dark there was.

But at least this much is clear. To build a brain with instinctive abilities, the Genome Organizing Device lays down separate circuits with suitable internal patterns that allow them to carry out suitable computations, then links them with appropriate inputs from the senses. In the case of a digger wasp or a cuckoo, such modules may have to “get the behavior right” the first time and may be comparatively indifferent to experience. But in the case of the human mind, almost all such instinctive modules are designed to be modified by experience. Some adapt continuously throughout life; some change rapidly with experience, then set like cement. A few just develop according to their own timetable. In the rest of this book, I propose to try to find the genes responsible for building—and changing—these circuits.

PLATONIC UTOPIA

One of the besetting sins evident in the nature–nurture debate has been utopianism, the notion that there is one ideal design for society, which can be derived from a theory of human nature. Many of those who thought they understood human nature promptly turned description into prescription and set out a design for the perfect society. This practice is common among those on the nature side of the debate as well as those on the nurture side. Yet the only lesson to be drawn from utopian dreaming is that all utopias are hells. All attempts to design society by reference to one narrow conception of human nature, whether on paper or in the streets, end in producing something much worse. I propose to end each chapter mocking the utopia implied in taking any theory too far.

William James and the protagonists of instinct did not, as far as I can discern, write about a utopia. But Plato’s Republic, the father of all utopias, is in many ways close to a Jamesian dream. It is imbued with a similar nativism. The Republic has been called a “managerial meritocracy” in which the same education is available to all, so the top jobs go to those with the innate talent for them. In Plato’s metaphorical republic (which was probably never intended as a political blueprint), everything is governed by strict rules. The “rulers,” who make policy, are assisted by the “auxiliaries,” who provide a sort of civil and defense service. Together these two classes are called the “guardians,” and they are chosen on merit, which means on native talent. But to prevent corruption, the guardians live lives of austere asceticism, unable to own property, to marry, or even to drink from gold cups. They live in a dormitory, but their miserable existence gladdens their hearts because they know it is for the good of the society as a whole.

Karl Popper was not the first, nor will he be the last, philosopher to call Plato’s dream a totalitarian nightmare. Even Aristotle pointed out that there was not much point in a meritocracy if merit did not bring rewards—of wealth and sex as well as power: “Men pay most attention to what is their own: they care less for what is common.” Plato’s citizens were expected to accept any spouse nominated by the state, and (if female) to suckle any baby. There is little chance of that; but grant Plato the backhanded compliment of having this insight, at least: even a meritocracy is an imperfect society. If all people receive the same education, then the differences in their abilities will be innate. A truly equal-opportunity society merely rewards the talented with the best jobs and relegates the rest to doing the dirty work.

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