but that is exactly the point: Most women are neither young nor beautiful, nor are they trying to seduce strange men: It is hard to overemphasize how unusual humans are in this respect: Males in some monogamous bird species such as pigeons and doves' do take care to select a female carefully, but in many other birds, the males are happy to have a fling with any passing female, as the evidence of sperm competition theory has demonstrated (chapter 7). Although he may prefer variety more than females do, man is a highly sexually selective male as males go:
Selectivity by one or the other sex is the prerequisite of sexual selection. And as I have argued in previous chapters, it is more than that. It is the almost invariant predictor of sexual selection: Fisher ' s runaway process for sexy sons and Zahavi-Hamilton 's Good-genes effect simply cannot be avoided once one or the other sex is being selective. So we should actually expect some exaggeration of some feature or other in :man as a simple consequence of sexual selection.'
Incidentally, Miller 's argument draws attention to a little-appreciated aspect of sexual selection: It can affect both the selected sex and the selector: For example, among American blackbirds those species in which the female is large are also the species in which the male is much larger. The same is true of many mammals and birds: Among grouse, pheasants, seals, and deer, a greater ratio between male and female size occurs in the larger species: A recent analysis of this effect concludes that it is caused by sexual selection: The more polygamous the species, the more premium there is on large size in males; the more males are selected for large size, the more they inevitably leave large-size genes to their daughters as well as their sons. Genes can be 'sex-linked' but usually only imperfectly or when there is a strong disadvantage to a daughter 's
inheriting the effect—as in the case of female birds and gaudy colors. Thus, sexual selection by males of females for large brains would result in larger brains for both sexes. fe OBSESSED WITH YOUTH
I believe that Miller 's tale deserves a special twist from the neoteny theory (although he is not convinced). The neoteny theory is well established among anthropologists.: And the notion of human monogamous child rearing is well established among sociobiologists: Nobody has yet put the two together: If men began selecting mates that appeared youthful, then any gene that slowed the rate of development of adult characteristics in a woman would make her more attractive at a given age than a rival: Consequently, she would leave more descendants, who would inherit the same gene. Any neoteny gene would give the appearance of youthfulness. Neoteny, in other words, could be a consequence of sexual selection, and since neoteny is credited with increasing our intelligence (by enlarging the brain size at adulthood), it is to sexual selection that we should attribute our great intelligence.
The idea is hard to grasp at first, so a thought experiment may help: Imagine two primeval women: One develops at the normal rate, and the other has an extra neoteny gene so that she is hairless of body, large-brained, small-jawed, late maturing, and long-lived: At the age of twenty-five, both are widowed; each has had one child by her first husband: The men in the tribe have a preference for young women and twenty-five is not young, so neither stands much chance of getting a second husband. But there is one man who cannot find a wife: Given the alternatives, he chooses the younger-looking woman. She goes on to have three more children while her rival barely manages to rear the one she already had: The details of the story do not matter. The point is that once males prefer youth, a gene for delaying the signs of aging would generally prosper at the expense of a normal gene, and a neoteny gene does exactly that. The gene would probably make the THE I NTELLECTUAL CHESS GAME
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woman 's sons appear neotenized as well as her daughters, for there is no reason that it should be specific to the female sex in its effects. The whole species would be driven into neoteny.
Christopher Badcock, a sociologist at the London School of Economics who unusually combines an interest in evolution and an interest in Freud, has proposed a similar idea. He suggested that neotenic (or, as he calls it, 'paedomorphic ') traits were favored by female choice rather than male choice. Younger males, he suggests, made more cooperative hunters, and therefore females who wanted meat picked younger-looking men. The principle is the same: Neotenic development is a consequence of a preference for it in one sex. 59
This is not to deny that bigger brains themselves brought advantages in Machiavellian intelligence or language or seductive-ness. Indeed, once these advantages became clear, men who were especially fussy about picking youthful-looking women would be most successful because they sometimes picked neotenic, big-brained women and therefore had more intelligent children. But it does suggest an escape from the question Why did it not happen to baboons?
However, Miller 's sexual selection idea suffers from a near fatal flaw. Remember that it presupposes sexual choosiness by one or other sex. But what caused that choosiness? Presumably the cause was the fact that men took part in parental care, which gave women an incentive to confine probable paternity to one man and gave men an incentive to enter into a long-term relationship as long as he could be certain of paternity. Why then did men take part in parental care? Because by doing so they could increase the chances of rearing a child more than by trying to seek new partners.
The reason for this was that children, unusual for ape infants, took a long time to mature, and men could help their wives during child rearing by hunting meat for them. Why did they take a long time to mature? Because they had big heads! The argument is circular.
That may not be fatal to it. Some of the best arguments, such as Fisher 's theory of runaway sexual selection, are circular.
The relationship between chickens and eggs is circular. Miller is
actually rather proud of the theory ' s circularity because he believes we have learned from computer simulation that evolution is a process which pulls itself up by its bootstraps: There is no single cause and effect because effects can reinforce causes: If a bird finds itself to be good at cracking seeds, then it specializes in ,cracking seeds, which puts further pressure on its seed-cracking ability to evolve. Evolution is circular:
STALE MATE
It is a disquieting thought that our heads contain a neurological version of a peacock 's tail—an ornament designed for sexual display whose virtuosity at everything from calculus to sculpture is perhaps just a side effect of the ability to charm. Disquieting and yet not altogether convincing. The sexual selection of the human mind is the most speculative and fragile of the many evolutionary theories discussed in this book, but it is also very much in the same vein as the others: I began this book by asking why all human beings were so similar and yet so different, suggesting that the answer lay in the unique alchemy of sex: An individual is unique because of the genetic variety that sexual reproduction generates in its perpetual chess tournament with disease. An individual is a member of a
