Susan Brownmiller gives her take on the original subjugation of women in 1975's Against Our Will: Men, Women, and Rape, asserting that ancient man's discovery that he possessed the ability to rape was likely the beginning of man's oppression of women. And here's Andrea Dworkin's version, excerpted from her 1974 book Woman Hating:
"Even patriarchy and misogyny began somewhere. Here I can only guess. We know that at one time men were hunters and women were planters. Both demanded incredible physical strength and considerable knowledge and skill. Why did men hunt and women plant? Clearly women planted because they were often pregnant, and though pregnancy did not make them weak and passive, it did mean that they could not run, go without food for long periods of time, survive on the terms that hunting demanded. It is probable that very early in human history women were also hunters, and that it was crucial to the survival of the species that they develop into planters - first to supplement the food supply, second to reduce infant and woman mortality. We see that the first division of labor based on biological sex originated in a fundamental survival imperative. In the earliest of times, with no contraception and no notion of the place of the man in the process of impregnation, women were invested with a supreme magical power, one which engendered awe and fear in men. As they developed skill in planting, they embodied even more explicitly fertility, generation, and of course death. The overwhelming mana of women, coupled with the high mortality which went along with childbirth, could well have led to practices of protection, segregation, and slowly increasing social restriction. With pregnancy as the one inevitable in a woman's life, men began to organize social life in a way which excluded woman, which limited her to the living out of her reproductive function. As men began to know power, that power directly related to the exclusion of women from community life, the myth of feminine evil developed and provided justification for laws, rites, and other practices which relegated women to pieces of property. As a corollary, men developed a taste for subjugating others and hoarding power and wealth which characterizes them to this very day."