Warring Leviathans: Conflict Among Hierarchies and the Evolution of Human Prosociality

Research into the origins of human prosocial cooperation has suggested a central role for institutions of coercive sanctioning, by which society as a whole can punish those who fail to contribute to collective goods. Less attention, however, has been paid to the conditions under which such institutions emerge and persist over time. We argue that intergroup conflict, by significantly increasing the returns to collective goods, makes the creation of coercive centralized hierarchy more likely, and therefore increases within-group cooperation. Further, we argue that when such institutions are constructed over time rather than all at once, institutions which were built up during conflict can be ex-post efficient even in times of peace and therefore can outlast the conflicts which provided their initial impetus. We develop this argument using a computational model, and validate the results using a networked public goods game experiment. This research has implications for the study of social institutions at a variety of levels, from small societies to states.