"[T]here are mostly men at the top [and] at the bottom"
That's consistent with analysis by Howard Wainer[1] on gender differences:
"[I]t has been well established that there is an overabundance of boys at the high end of test score distributions. [S]ome observers have used such results to make inferences about differences in intelligence between the sexes. [H]owever, most enlightened investigators have seen that it is not necessarily a difference in level but a difference in variance that separates the sexes. Thus, while there are more boys at the high end, there are also more at the low end."
[1] The Most Dangerous Equation http://press.princeton.edu/chapters/s8863.pdf