In our species, males invest in their children. They try to get a sense of which kids are theirs and they invest in them. That's why romantic love exists. It's possible that that purpose is subordinate to a larger purpose that is still unfolding. A species that begins to evolve culturally can eventually lead to who knows where.
Culture is like clothing.
The purpose of clothing is to keep us warm. Its fit or design is just secondary. In the same way, the primary and secondary issues of culture can get confused. Historians spend too much time talking about the superficial differences in cultures and not enough time talking about their fundamental similarities. But for a few historical flukes, they would have had those revolutions before the West.