Beyond the inequalities of class and caste lay those of slavery, a social institution with deep roots in human history. Some have suggested that the early domestication of animals provided the model for enslaving people.7 Certainly slave owners have everywhere compared their slaves to tamed animals. Aristotle, for example, observed that the ox is “the poor man’s slave.” War, patriarchy, and the notion of private property, all of which accompanied the First Civilizations, also contributed to the growth of slavery. Large-scale warfare generated numerous prisoners, and everywhere in the ancient world capture in war meant the possibility of enslavement. Early records suggest that women captives were the first slaves, usually raped and then enslaved as concubines, whereas male captives were killed. Patriarchal societies, in which men sharply controlled and perhaps even “owned” women, may have suggested the possibility of using other people, men as well as women, as slaves. The class inequalities of early civilizations, which were based on great differences in privately owned property, also made it possible to imagine people owning other people.