[inigyou]

also, women and men mostly have the same genes. Anything that affects one affects the other, by default.

This fact is itself subject to evolution. (In birds, it's the women who have the different chromosome.) Mammals may have evolved to share most genes between sexes because that allows either sex to benefit from traits evolved by the other one, and not solely because it's the easy way to store genes.

Did you know men have a genetic breast size?