Decoding Love - Andrew Trees [18]
If a man could have sex with an unlimited number of women and conceive with all of them, he could theoretically father hundreds of children in one year, and some famous historical figures have indefatigably attempted to do just that. According to historical records, Moulay Ismael the Bloodthirsty, the emperor of Morocco from 1672 to 1727, fathered 888 children. Recent DNA evidence suggests that Genghis Khan might have fathered an even larger number, and according to research, a mere nineteen male lineages have played the dominant role in populating the world, a remarkable example of the multiplying power of sexual selection for successful males.
Now, consider the woman and her egg, which is a very precious commodity indeed. A woman ovulates once a month, and once she is pregnant, she must carry that child inside of her for nine months. Even after she has the baby, she will have to care for it, and she is unlikely to get pregnant again right away because breast-feeding makes it more difficult to conceive. Over the course of her lifetime, the typical woman will have approximately four hundred to five hundred ovulations. Compare that to the trillions of sperm men will produce over the course of their lifetime (of course, the egg is 85,000 times larger than an individual sperm). Let’s assume that she manages to have one baby a year during all of her fertile years. It’s possible she could crack twenty. The record is an astounding sixty-nine, which an eighteenth-century Russian achieved by repeatedly having twins (although this figure is possibly apocryphal). Even that extreme number—any woman who has been pregnant will shudder at the thought—pales in comparison to the number of children a man can father, even if he isn’t Ismael the Bloodthirsty. If you are still unconvinced, anthropological evidence also confirms that cheap sperm-precious egg distinction. Seventy percent of human societies involve a payment between the two families. Any guesses as to what percentage of those require a payment to the bride’s family? Ninety-six percent!
Trivers’s brilliant insight was to realize the enormous ramifications of this simple difference. For a man, the ideal approach from an evolutionary standpoint—passing along his genes to as many children as possible—is to sleep with as many women as possible. And he shouldn’t worry too much about the quality of those women. Ugly women, pretty women, women with no teeth, women who can’t spell unilateral—it doesn’t matter. Having sex with them costs him very little effort, and all of them provide an opportunity to pass along his DNA. For a woman, though, the ideal approach is to be as selective as possible. With so few opportunities in a lifetime, she wants to ensure that she gets quality genetic material from the father. So, for her, it makes a great deal of difference whether the father is a bright, attractive, funny guy who likes to read Jane Austen or a slack-jawed, humor-less oaf who mistreats his dog. Hence, the battle of the sexes—a constant war between men who want to seduce with as little work as possible and women who want to resist until they are sure that the potential father is genetically superior and committed to help. As one research team writes, evolution favors males who are “aggressive sexual advertisers” and females who are “coy, comparison shoppers.”
Ah, but wait! We have left out one crucial wrinkle: pair-bonding. In our case, the legal bond between man and wife, which changes the calculus considerably. With marriage, a man is tied to a woman for life. With divorce rates running at almost