WHY ARE PRETTY GIRLS SO DUMB? 2: Who knew that the post I'd get the most comments on ever would be about pretty girls being dumb? Maybe I've found my niche!
More seriously though, I've thought of a genetic angle to the question. I'm sure this is obvious to real biologists out there, but here it is anyway because I thought of it myself: men may show more variation in intelligence because they exhibit recessive genes carried on the X chromosome more strongly than women do. This is because men only have one X (and one Y); women have two Xs, of course, and any recessive genes carried on one of the two Xs will be damped out if there is a dominant gene on the other X. A man who gets a recessive gene on his one X will display it more strongly. One example of this is that while 1/12th of males are color-blind only 1/144th of females are -- due to the fact that the color-blindness gene is recessive and located on the X chromosome.
If there are equivalent genes for certain types of intelligence, then it's clear that sex-linkage could account for the greater standard deviation in intelligence among men, even though both genders have the same mean intelligence.
Update:
I asked the girl from my population genetics class about my theory and she gave it a resounding endorsement: "yeah, maybe". QED.
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