A lack of meaningful difference in male and female brains actually supports Summers's explanation of greater male variability. Because of X chromosome mosaicis

A lack of meaningful difference in male and female brains actually supports Summers's explanation of greater male variability. Because of X chromosome mosaicism being one looming factor decreasing female variability (see photographs here: [1]), female brains would have to "catch up" in terms of variance through some other sex differences in how brains function. Obviously, some difference in programming, via "hormones" or whatever, could do it by using different sets of information at the time the brain is constructed. The article is stating that we lack one form of evidence of this. I'd guess it would also be extra difficult for sex-specific brain differences in high-level structure to evolve when X chromosome inactivation happens quasi-randomly. But nature can surprise you... [1] https://www.nytimes.com/2014/01/21/science/seeing-x-chromosomes-in-a-new-light.html https://www.nytimes.com/2014/01/21/science/seeing-x-chromoso...