Why do men have greater variance than women in mental test scores?
I've heard two theories related to genetics. Mental traits are massively polygenic (many genes with tiny effects). Men (XY) do not have a duplicate X chromosome like women (XX), which means that mutations to an X chromosome that disrupt typical gene expression can affect men more than women, driving variance in mental scores. The second theory is related to the fact that individual men are less likely to pass on their genes than individual women. Counter-intuitively, most of our ancestors are women. Men may have evolved a riskier genetic strategy that produces more high and low cognitive scores in phenotypes. Consider that men also take more risks. This is a behavioral outcome that may have emerged from the same selection pressure.

See also:

https://en.wikipedia.org/wiki/The_Bell_Curve

https://www.amazon.com/Intelligence-That-Matters-Stuart-Ritchie/dp/1444791877