Of course it takes two to make a child, but under all appearances women have had the biological imperative to raise the children while the men's single innate objective is to mate with as many women as possible. While it is technically possible to rise above these instincts to get rid of gender roles, do we really want to? Sexism is almost dead anyway :\
http://books.google.com/books?id=3_0...esult&resnum=1
http://en.wikipedia.org/wiki/Biologi...e#Reproduction