BUT if evolution didn’t determine human behavior, what did?

Of course, no fossilized record can really tell us how people behaved or thought back then, much less they behaved or thought as they did.

Nonetheless, something funny happens when social scientists claim that a behavior is rooted in our evolutionary past.

The evolutionary psychologists of the 1980s and ’90s built on Mr. Schmitt used parental investment theory to explain why men should be expected to “devote a larger proportion of their total mating effort to short-term mating.” Because men invested less time and effort in their offspring, they evolved toward promiscuity, while women evolved away from it.

Trivers’s theory to explain a wide array of stereotypical gender differences in mating. Promiscuity, the researchers hypothesized, would have been more damaging to the female reputation than to the male reputation.

If a man mated with a promiscuous woman, he would never be able to ensure his paternity.

Men, on the other hand, could potentially enhance their status by pursuing a short-term mating strategy.

In fact, women reported slightly more sexual partners (a mean of 4.4) than did men (a mean of 4.0).

In 2009, another long-assumed gender difference in mating — that women are choosier than men — also came under siege. By manipulating this component of the gender script, the researchers discovered that women became less selective — they behaved more like stereotypical men — while men were more selective and behaved more like stereotypical women.

Assumptions about that behavior take on the immutability of a physical trait — they come to seem as biologically rooted as opposable thumbs or ejaculation.

Using evolutionary psychology to back up these assumptions about men and women is nothing new.

Men reported having had more sexual partners than women.