Here’s something to look forward to: New research finds that women’s sexual satisfaction may actually improve as they get older.

The study, published in the January issue of the American Journal of Medicine, looked at such sexual satisfaction-related factors as hormone use, frequency of arousal, lubrication, orgasm and pain during sexual intercourse along with sexual desire and satisfaction among 806 women ages 40 to 100 (median age 67; 63 percent post-menopausal).

The researchers found that, while sexual activity declined as women aged, about half of those age 80 or older reported being sexually satisfied most or all of the time.

This discovery is not surprising. What's really surprising is that human males desire younger women more than older women. True, this is not surprising if you compare humans with other humans, but it is surprising if you compare humans with other primates. And for a comparison to have any value or substance it must compare the human animal with other animals.

Anyone who has glanced at the literature concerning chimpanzees (the human animal's closest relative) realizes that male chimps prefer established females, powerful females, females who have had even several children. Indeed, with bonobos (our erotic relative), young females are practically ignored and have to force themselves onto males. (Read Our Inner Ape by the Dutch primatologist Frans de Waal—however, much of his information on wild bonobos is drawn from the findings of Japanese researchers.)

So why do human males prefer younger women? Evolutionary psychology always has this dumb answer: Youth equals fertility. But if this is a natural law for us civilized humans, why is it not the law of the jungle? It seems we have completely mistaken a cultural phenomenon for a biological one. It is very likely that the desire for young women has no natural basis but is instead entirely a cultural construction. Indeed, the best sociobiologist in the business, Sarah Hrdy, goes as far as to see this strange kind of desire as emerging from the cultural institution of marriage. (In her brilliant paper "Female Sexuality and the Prehominid Origins of Patriarchy," Hrdy argues that youth has its value in the context of a long-term investment.)

And marriage only makes sense in the context of property relations. And cultures of property relations are mostly realized in agricultural or sedentary societies. And because these kinds of societies are new in the world, the desire for young women is not at all ancient, or profound, or in our blood. It's in our heads.

Another point Hrdy makes: "I am with my fellow feminist, evolutionary biologist Patricia Gowaty, who has argued that male preferences for neotenous traits might be due to juveniles being easier to dominate."