In almost every human society some people get more and others get less. Why is inequity the rule in these societies? In The Origins of Unfairness, philosopher Cailin O'Connor firstly considers how groups are divided into social categories, like gender, race, and religion, to address this question. She uses the formal frameworks of game theory and evolutionary game theory to explore the cultural evolution of the conventions which piggyback on these seemingly irrelevant social categories. These frameworks elucidate a variety of topics from the innateness of gender differences, to collaboration in academia, to household bargaining, to minority disadvantage, to homophily. They help to show how inequity can emerge from simple processes of cultural change in groups with gender and racial categories, and under a wide array of situations. The process of learning conventions of coordination and resource division is such that some groups will tend to get more and others less. O'Connor offers solutions to such problems of coordination and resource division and also shows why we need to think of inequity as part of an ever evolving process. Surprisingly minimal conditions are needed to robustly produce phenomena related to inequity and, once inequity emerges in these models, it takes very little for it to persist indefinitely. Thus, those concerned with social justice must remain vigilant against the dynamic forces that push towards inequity.