Actually there is a very good biological explanation for why this is the case: men are more varied than women. Because until the modern era men were expendable and the victors impregnated the women for the next generation.
> I don't understand how that theory would make women less varied.
Look up sexual selection and dimorphism lectures from a respectable university. There's a huge body of evidence about the variation between sexes and a lot of it is beyond me since I'm not a biologist.
It explains rather well how the male population distributions get "cut off" as a result of sexual selection with constraint to resources.
Because the men are able to evolve some things separately from women (eg on the Y chromosome) and versa - mitochondria is from the mother. And even if this was not the case - some genes express themselves only in men (D'OH) like testosterone and baldness.
http://www.denisdutton.com/baumeister.htm