To follow up on the previous posting (and thanks very much to phip for galvanizing the discussion, by the way), this morning NPR's Weekend Edition ran a short piece on the other gender gap, namely, the fact that American women are now earning 200,000 more bachelor's degrees per year than American men. As with the gender gap in the upper ranks of science, this one also invites biological explanations, apparently: one of the people interviewed opined that "Any mother who has had both sons and daughters knows that the little boys are different from the little girls." His implication, as I understood it, was that little boys are less suited to the kind of steady application that college requires. But this supposedly essential difference between the sexes has emerged only over the past 30 years, since until recently, male students predominated at colleges and universities.
Either evolution proceeds much more quickly than we've been led to believe, or a cultural sea change is at work.