hierarchies and inequalities are not unique to state societies, but there is little doubt that the rise of the state introduced a radical change in the realm of human politics. For the first time in human history, political systems brought millions of individuals under one rule, creating unknown opportunities for collective action as well as exploitation. This chapter aims to explain this phenomenon from a viewpoint that may look unfamiliar to students of the state and of its origin. I am not seeking to legitimize the existence of the state, as contract theorists have traditionally done, by identifying the reasons that people would have to accept its rule. Nor am I looking for an explanation of specific transitions to statehood, as historians, anthropologists, and archaeologists do with great competence.

Instead, as in the previous chapter, my goal is to explain how the recurrence and stability of certain institutional outcomes can be explained by the cognitive and motivational mechanisms underlying human cooperation. It is the recurrence and stability of certain types of outcomes that I seek to explain, not the emergence of specific outcomes, such as the construction of the state in China or in Mesoamerica. The underlying epistemological assumption is simple. Some explanatory factors might be essential to account for regularities at the population level, but these same factors might be only loosely relevant in accounting for particular cases.