Why Is Sex Fun__ The Evolution of Human Sexuality - Jared M. Diamond [34]
At that time the female’s belly was not yet visibly bulging, and the deceived males had no idea that they were utterly wasting their efforts. Females finally ceased copulating during the latter half of pregnancy, when the males could no longer be deceived. That still left most males in the troop ample time to have sex with most of the troop’s females. One-third of the males were able to copulate with every single female. Thus, through concealed ovulation female vervets ensured the benevolent neutrality of almost all of the potentially murderous males in their immediate neighborhood.
In short, Hrdy considers concealed ovulation an evolutionary adaptation by females to minimize the big threat to their offsprings’ survival posed by adult males. Whereas Alexander and Noonan view concealed ovulation as clarifying paternity and reinforcing monogamy, Hrdy sees it as confusing paternity and effectively undoing monogamy.
At this point, you may be starting to wonder about a potential complication in both the daddy-at-home theory and the many-fathers theory. Why is human ovulation concealed from women as well, when all that’s required by either theory is for women to conceal ovulation from men? For example, why couldn’t women keep their derrières the same shade of red every day of the month to deceive men, while still remaining aware of sensations of ovulation and just faking an interest in sex with lusty men on non-ovulatory days?
The answer to that objection should be obvious: it would be hard for a woman convincingly to fake sexual receptivity if she felt turned off and knew that she was currently infertile. That point applies with particular force to the daddy-at-home theory. When a woman is involved in a long-lasting monogamous relationship in which the partners come to know each other intimately, it would be hard for her to deceive her husband unless she herself were deceived as well.
There is no question that the many-fathers theory is plausible for those animal species (and perhaps those traditional human societies) in which infanticide is a big problem. But the theory seems hard to reconcile with modern human society as we know it. Yes, extramarital sex occurs, but doubts about paternity remain the exception, not the rule that drives society. Genetic tests show that at least 70 percent, perhaps even 95 percent, of American and British babies really are sired legitimately, that is, by the mother’s husband. It’s hardly the case that for each kid there are many men standing around radiating benevolent interest, or even showering gifts and dispensing protection, while thinking, “I may be that kid’s real father!”
It therefore seems unlikely that protecting kids against infanticide is what propels women’s constant sexual receptivity today. Nevertheless, as we’ll now see, women may have had this motivation in our distant past, and sex may have subsequently assumed a different function that now sustains it.
How, then, are we to evaluate these two competing theories? Like so many other questions about human evolution, this one can’t be settled in the way preferred by chemists and molecular biologists, a test-tube experiment. Yes, we’d have a decisive test if there were some human population whose women we could cause to turn bright red at estrus and to remain frigid at other times, and whose men we could cause to be turned on only by bright red women. We