On a tour of the Galápagos Islands, we had the opportunity to visit a field of Galápagos giant turtles, some who may have been the grandchildren or great-grandchildren of the same turtles Charles Darwin saw when he visited the islands in the 1820s (they can live to be more than 100 years old). Our guide told the group that, unlike humans and other mammals, male and female Galápagos turtles arenot genetically different. For these turtles, as well as for other reptiles including alligators and crocodiles, sex is not determined by differences in genes, but by differences in the temperature at which the eggs are incubated. We could, theoretically, have genetically identical twin turtles, one a male and one a female. The guide told us the mnemonic he uses to remember the relationship between incubation temperature and sex for Galápagos giant turtles: “Hot chicks and cool dudes.”

The idea that women and men might actually think differently, that is have different preferred modes of thinking or different thinking abilities, came up in both classes. At the time, it seemed clear to me that any between-sex differences in thinking abilities were due to socialization practices, artifacts and mistakes in the research, and bias and prejudice. After reviewing a pile of journal articles that stood several feet high and numerous books and book chapters that dwarfed the stack of journal articles, I changed my mind. The task I had undertaken certainly wasn’t simple and the conclusions that I had expected to make had to be revised.

The literature on sex differences in cognitive abilities is filled with inconsistent findings, contradictory theories, and emotional claims that are unsupported by the research. Yet, despite all of the noise in the data, clear and consistent messages could be heard. There are real, and in some cases sizable, sex differences with respect to some cognitive abilities. Socialization practices are undoubtedly important, but there is also good evidence that biological sex differences play a role in establishing and maintaining cognitive sex differences, a conclusion that I wasn’t prepared to make when I began reviewing the relevant literature.

Men and women have different bodies. The differences are the direct result of evolution. Women’s bodies evolved to suit the demands of bearing and rearing children and of gathering plant food. Men’s bodies evolved to suit the demands of rising in a male hierarchy, fighting over women, and providing meat to a family.

Men and women have different minds. The differences are the direct result of evolution. Women’s minds evolved to suit the demands of bearing and rearing children and of gathering plant food. Men’s minds evolved to suit the demands of rising in a male hierarchy, fighting over women, and providing meat to a family.

The first paragraph is banal; the second inflammatory.

Silver hair and furrowed brows allow aging men to look “distinguished.” That is not the case with aging women, who risk marginalization as “unattractive” or ridicule for efforts to pass as young. This double standard leaves women not only perpetually worried about their appearance, but also worried about worrying.

[A] man’s attractiveness in short-term mating contexts is just as important to women as a woman’s attractiveness is to men when men evaluate long-term mates.