(I) Patriarchy does not simply mean that men rule. (II) Otherwise, through a process of cultural evolution, societies that adopted this particular social system maximized their population. (III) Indeed, it is a particular value system that not only requires men to marry but to marry a woman of proper station. (IV) It competes with many other male visions of good life, and for that reason alone is prone to come in cycles. (V) Yet before it degenerates, it is a cultural regime that serves to keep birth-rates high among the affluent while also maximizing parents' investments in their children.