This contradicts Freud 's idea that incest taboos are there because people need to be told not to commit incest. Indeed, Freud ' s theory requires that evolutionary pressures have not just failed to generate some mechanism to avoid incest but have actually encouraged maladaptive incestuous instincts, which the taboos repress. Freudians have often criticized the Westermarck theory on the grounds that it would obviate the need for incest taboos at all.
But in fact incest taboos that outlaw marriage within the nuclear family are rare. The taboos that Freud observed are nearly always concerned with outlawing marriage between cousins: In most societies there is no need to outlaw incest within the nuclear family because there is little risk of its happening:'
So why are the taboos there? Claude Levi-Strauss invented a different theory called the "alliance theory, " which stressed the importance of using women as bargaining chips between tribes and therefore not letting them marry within the tribe, but since no two anthropologists can agree on exactly what Levi-Strauss meant, it is hard to test his idea. Nancy Thornhill of the University of New Mexico has argued that the so-called incest taboos are actually rules about marriage customs invented by powerful men CO prevent rivals from accumulating wealth by marrying their own cousins.
They are not about incest at all but about power:'
TEACHING OLD CHAFFINCHES NEW TRICKS
The incest story neatly demonstrates the interdependence of nature and nurture. The incest avoidance mechanism is socially induced: You become sexually averse to your siblings during your childhood: THE USES OF BEAUTY
::: 285 :::
In that sense there is nothing genetic about it: And yet it is genetic, for it is not taught: It just develops within the brain. The instinct not to mate with childhood companions is nature, but the features by which you recognize them are nurture.
It is critical to Westermarck ' s argument that this aversion to mating with familiar people wear off for new acquaintances in later life: Otherwise, people would become averse to mating with their spouses within weeks of marrying them, which they plainly do not. Biologically, this is not hard to arrange: One of the most striking features of animal brains is the "critical period " of youth during which something can be learned and after which the learning is not erased or superseded: Konrad Lorenz discovered that chicks and goslings "imprint " on the first moving thing they meet, which is usually their mother and rarely an Austrian zoologist, and thereafter they prefer to follow that object: But chicks a few hours old will not imprint, nor will those two days old: They are at their most sensitive to imprinting at thirteen to sixteen hours old. During that sensitive period they will fix their preferred image of a parent in their heads:
The same is true of a chaffinch learning to sing: Unless it hears another chaffinch, it never learns the species 's typical song. If it hears no chaffinch until it is fully grown, it never learns the right song but produces a feeble half-song. Nor will it learn the song if it hears another chaffinch only when it is a few days old. It must hear a chaffinch during a critical period in between—from two weeks to two months of age—and then it will learn to sing correct-ly; after that period it never modifies its song by imitation:'
It is not hard to find examples of critical-period learning in people: Few people change their accents after the age of about twenty-five, even if they move from, say, the United States to Britain: But if they move at ten or fifteen, they quickly adopt a British accent: They are just like white-crowned sparrows, which sing with the dialect of the place where they lived at two months old:9 Likewise, children are remarkably good at picking up foreign languages just by exposure to them, whereas adults must laborious-ly learn them: We are not chicks or chaffinches, but we still have
::: 286 :::
The Red Queen
critical periods during which we acquire preferences and habits that are fairly hard to change.
This concept of the critical period is presumably what lies behind the Westermarck incest-avoiding instinct: We become sexually indifferent to those with whom we were reared during a critical period. Nobody is certain exactly what constitutes the critical period, but it is a plausible guess that it lasts from, say, eight to fourteen, the years before puberty. Common sense dictates that sexual orientation must be decided in such a fashion: A genetic predisposition meets examples during a critical period. Recall the fate of the baby chaffinch. For six weeks it is sensitive to learning chaffinch song. But during those six weeks of sensitivity, it hears all sorts of things: cars, telephones, lawn mowers, thunder, crows, dogs, sparrows, starlings. Yet it only imitates the song of chaffinches. It has a predilection to learn chaffinch song. (If it were a thrush or a starling, it could indeed imitate some of the other things. One bird in Britain learned the call of a telephone, causing havoc among backyard sunbathers.)'° This is often the case with learning: Ever since the work of Nikolaas Tinbergen and Peter Marler in the 1960s, it has been well known that animals do not learn anything and everything; they learn what their brains " want" to learn: Men are instinctively attracted to women thanks to the interaction of their genes and hormones, but that tendency is much influenced in a critical period by role models, peer pressure, and free wilclass="underline" There is learning, but there are predispositions.
A heterosexual man emerges from puberty with more than a general sexual preference for all women: ,He emerges with a distinct notion of beauty and ugliness. He is "stunned " by some women, indifferent to others, and finds others sexually repulsive. Is this, too, something that he acquired by a mixture of genes, hormones, and social pressure? It must be, but the interesting question is how much of each. If social pressure is everything, then the images and lessons we give to the youth of both sexes, through films, books, advertisements, and by example, are crucially important: If not, then the fact that men prefer, say, thin women is fixed by the genes and hormones and not a passing fad.
THE USES OF BEAUTY
::: 287 :::
Suppose you were a Martian interested in studying people as William Thorpe studied chaffinches. You want to know how men learn their standards of beauty, so you keep boys in cages. Some you expose to endless films of plump men admiring and being admired by plump women, while thin men and thin women are reviled; others you keep in total ignorance of womanhood so that their existence comes as a shock at the age of twenty.
It is revealing to speculate on what you think the outcome of the Martian 's experiment would be because what follows is an attempt to piece together from much inferior experiments and facts the same result: What kind of woman would the men who had never seen women prefer once they got over the shock of seeing women for the first time? Old ones or young ones, fat ones or thin ones? And would the men reared to believe that fat was beautiful really prefer plump women to skinny models?
Bear in mind the reason we are concentrating on male preferences. As we saw in the last chapter, men care more about the physical appearance of women than vice versa, and for good reason: Youth and health are better clues to women's value as a mate and potential mother than to a man's: Women are not indifferent to youth and health, but they are more concerned than men with other features.
SKINNY WOMEN
But fashions change: If beauty is subject to fashion, however despotic, it can change. Consider a case where the definition of beauty does seem to have changed drastically in recent years: thinness. Wallis Simpson, later the Duchess of 'Windsor, is credited with the remark that a woman "can never be too rich or too thin, "