"Despite the admirable intentions of those who believe that patriarchy is solely a cultural invention, there is too much contrary evidence. Patriarchy is worldwide and history-wide, and its origins are detectable in the social lives of chimpanzees. It serves the reproductive purposes of the men who maintain the system. Patriarchy comes from biology in the sense that it emerges from men's temperaments, out of their evolutionary derived efforts to control women and at the same time have solidarity with fellow men in competition against outsiders. But evolutionary forces have surely shaped women, too, in minds as in bodies, in ways that both defy and contribute to the patriarchal system. If all women followed Lysistrata's injunctions and refused their husbands, they could indeed effect change. But they don't. Patriarchy has its ultimate origins in male violence, but it doesn't come from man alone, and it has its sources in the evolutionary interests of both sexes."