[Emu]

It pervades every part of life because it is life. The fact is, sex has always pervaded every part of life in one way or another. In most, if not all, ancient societies, rulers and the upper class always had harems, rulers having upwards of a thousand women all to themselves, from all over the area. Simpler tribespeople always had a god of fertility and the focus of their life was to have more children, for economic as well as spiritual reasons. A little closer to home, the Christian church has a way of policing everyone's sex life right down to the bedroom. In fact, anthropologists are beginning to believe that our large, powerful brains and everything that came forthwith (philosophy, mathematics, psychology, and anarcho-capitalism debates on the pristigeous i-Mockery forums) evolved as a result of a sexual arms race between men and women. The books I've read that explained it best were Matt Ridley's "The Red Queen" and Richard Dawkins' "The Selfish Gene."