Free The Moral Animal: Why We Are, the Way We Are: The New Science of Evolutionary Psychology by Robert Wright Page A

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    Female choice is notoriously hard to spot, and signs of its long-term effect are often ambiguous. Are males larger and stronger than females just because tougher males have bested their rivals and gotten to mate? Or, in addition, have females come to prefer tough males, since females with this genetically ingrained preference have had tougher and therefore more prolific sons, whose many daughters then inherited their grandmother's taste?
    Notwithstanding such difficulties, it's fairly safe to say that in one sense or another, females are choosy in all the great ape species. A female gorilla, for example, though generally confined to sex with a single, dominant male, normally emigrates in the course of her lifetime. When an alien male approaches her pack, engaging its leader in mutual threats and maybe even a fight, she will, if sufficiently impressed, decide to follow him. 38
    In the case of chimps, the matter is more subtle. The dominant, or alpha, male can have any female he wants, but that's not necessarily because she prefers him; he shuts off alternatives by frightening other males. He can frighten her too, so that any spurning of low-ranking males may reflect only her fear. (Indeed, the spurning has been known  {51}  to disappear when the alpha isn't looking.) 39 But there is a wholly different kind of chimp mating — a sustained, private consortship that may be a prototype for human courtship. A male and female chimp will leave the community for days or even weeks. And although the female may be forcibly abducted if she resists an invitation, there are times when she successfully resists, and times when she chooses to go peacefully, even though nearby males would gladly aid her in any resistance. 40
    Actually, even going unpeacefully can involve a kind of choice. Female orangutans are a good example. They do often seem to exercise positive choice, favoring some males over others. But sometimes they resist a mating and are forcibly subdued and — insofar as this word can be applied to nonhumans — raped. There is evidence that the rapists, often adolescents, usually fail to impregnate. 41 But suppose that they succeed with some regularity. Then a female, in sheerly Darwinian terms, is better off mating with a good rapist, a big, strong, sexually aggressive male; her male offspring will then be more likely to be big, strong, and sexually aggressive (assuming sexual aggressiveness varies at least in part because of genetic differences) — and therefore prolific. So female resistance should be favored by natural selection as a way to avoid having a son who is an inept rapist (assuming it doesn't bring injury to the female).
    This isn't to say that a female primate, her protests notwithstanding, "really wants it," as human males have been known to assume. On the contrary, the more an orangutan "really wants it," the less she'll resist, and the less powerful a screening device her reticence will be. What natural selection "wants" and what any individual wants needn't be the same, and in this case they're somewhat at odds. The point is simply that, even when females demonstrate no clear preference for certain kinds of males, they may be, in practical terms, preferring a certain kind of male. And this de facto discretion may be de jure. It may be an adaptation, favored by natural selection precisely because it has this filtering effect.
    In the broadest sense, the same logic could apply in any primate species. Once females in general begin putting up the slightest resistance, then a female that puts up a little extra resistance is exhibiting a valuable trait. For whatever it takes to penetrate resistance, the sons  {52}  of strong resisters are more likely to have it than the sons of weak resisters. (This assumes, again, that the relative possession by different males of "whatever it takes" reflects underlying genetic differences.) Thus, in sheerly Darwinian terms, coyness becomes its own reward. And this is