This is true, but why do these differences change so dramatically when you cross national borders? Specifically, Men have a higher variability in IQ in countries that have higher gender inequality. To me this seems to indicate that it's an issue of culture and the way men and women are socialized, not something biologically inherent to each sex.

Not related to IQ, but this study debunks the variability hypothesis in regards to mathematics performance: http://www.ams.org/notices/201201/rtx120100010p.pdf