This study claims that in affluent societies with more egalitarian cultures, gender differences are greater when it comes to measures of risk taking, patience, altruism, negative reciprocity etc...

Therefore, we should all be feminists because apparently, once women live in free egalitarian societies where they feel ‘empowered’, most of us will willingly and happily want to skip on over towards the feminine end of the spectrum.

Bonus for the ladies: men become more ‘manly’ too. Anecdata: I see this with my Icelandic friends.