None of this is especially surprising, but there's something so satisfying about having a chart with a straight line and a steep slope showing that the more egalitarian the country, the less constrained people are by stereotyped sex roles. That is progress.
The study fits with other recent research showing that supposedly gender-determined cognitive abilities, like math and spatial reasoning, are also a function of culture. The more egalitarian a society, the better girls are at algebra.
And that's the real lesson of evolutionary psychology. The main quality evolution acted on over all those millions of years was our ability to adapt. It's possible there are some ugly, genetically-predisposed legacies of jealousy and mate guarding and sexual deception rattling around in our great ape brains, but they're nothing compared to our capacity to form friendships, value a relationship independent of its ability to produce offspring, and love a highly evolved guy for baking a great loaf of bread.
Helmuth is Slate's science and health editor.