Seminar Two
Evolution of sexuality
Coevolution

We're back to our very first question: nature or nurture? Are such gender-typical behaviors fashioned by our gender, our culture, and/or our upbringing? Are there interwoven threads from genes, culture, and psychological development? Are Women from Venus, men from Mars? Sorry. The analogy is wrong. We all co-evolved, and coevolution can't occur apart!

Let's open another window on gender-typical behaviors: childhood play. In all cultures studied, from west to east and modern to pre-literate cultures, most boys engage in rough-and-tumble play and most girls in more sedate, relationship-oriented play.

Parents sometimes say, “My son was different from my daughter from the first day on the planet.” When the sexes grow up, men continue to show, on average, more physical violence and aggression than women. There are many exceptions; if we consider emotions, a woman can certainly be as psychologically “aggressive” (in loving or in hurtful ways) as any man.

At this point, where do we stand? Probably most of us agree that there are real differences in male and female sexual preferences, just as there are in other animals. Some of these differences are surely instilled culturally and developmentally; a parent may encourage gender-typical behavior and discourage gender-atypical behavior in their children.

But we haven't ruled out the possibility that some differences between the sexes are innate and predisposed to by genes and evolutionary logic. One way of asking the question might be: Is there an innate female human nature and male human nature?

Jared Diamond provides a good start to answering the question: There is a fundamental asymmetry in the interests of men and women, he writes. Once an ovum is fertilized, it's a woman's only chance to reproduce for at least another nine months, or probably several years under hunter-gatherer conditions of extended lactational amenorrhea (lack of menstrual periods while a woman provides breast milk for her baby). In contrast, in just a few minutes a man may increase his number of progeny. (This should remind us of A. J. Bateman's principle, discussed earlier.)

Evolutionary logic predicts that women should be more choosy about their mates. If natural and sexual selection have indeed influenced the differential survival of alleles (variants of genes) which predispose to mate choice, nature (biology) gains a measure of credibility. Nature does not operate in isolation, but together with nurture, or environment. We ignore either to our peril.