From Why we f*ck:

Much like today, when a landowner died others wanted the land, and the issue of who had legal claim to it had to be settled. The most intuitive arrangement was for a landowner’s offspring to inherit it. So for the first time ever, it became absolutely necessary for a man to know that his children were his. In the age before birth control and paternity tests, there was only one way for a man to be certain: He had to make 100 percent sure that his woman never, ever had sex with anyone else. And so men came to control land by controlling women’s sexuality, and the new “normal” sculpted by this economic trend is still the primary model for us today: sexual monogamy. To secure themselves economically, men demanded virgins and had zero tolerance for any hint of non-monogamy. Fidelity was enforced by vicious social contracts including religious dictates and cultural beliefs, for which women were humiliated, stoned or worse for even expressing the desire to bed with another man.

The author doesn’t cite any research, but this is certainly an interesting theory.