Cliodynamics

This essay suggests that the evolution of human cooperation should be viewed as a two-layer process. A foundational layer, rooted in subsistence and ecological pressures, shaped cooperative dispositions unevenly, whereas a reinforcing layer, rooted in conflict and stratification, facilitated large-scale cooperation in societies in which the seeds of cooperation had already formed while intensifying fragmentation elsewhere. The foundational layer unfolded over the grand arc of human evolution, reinforcing the capacity for small-scale cooperation in hunter-gatherer societies and favoring traits complementary to cooperation in some sedentary societies but not in others, as selective pressures diverged following the Neolithic Revolution. The reinforcing layer emerged as rising population density increased the returns to public infrastructure, heightened the risk of conflict, and increased the demand for social coordination. In environments where cooperation-enhancing traits were already present, these forces facilitated the emergence of institutions conducive to large-scale cooperation, whether voluntarily sustained or imposed through political authority and coercion. Yet in settings where such cultural foundations were absent, collective action was more challenging, and conflict was often destabilizing, magnifying division and political fragility. Recognizing the heterogeneity in cooperative predispositions produced by the foundational layer is therefore essential for identifying the origins of large-scale cooperation and the conditions under which conflict reinforced cooperative capacity rather than intensifying fragmentation