Human groups have long faced ecological threats such as resource stress and warfare, and must also overcome strains on coordination and cooperation that are imposed by growing social complexity. How do societies adapt to these challenges? Tightness-looseness (TL) theory suggests that ecological threat and social complexity both lead societies to become culturally tighter, with stronger norms and harsher punishment of deviant behavior. TL theory further predicts that tightening is associated

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... changes to political structure and intergroup relations. Building on research that tests TL theory's predictions in contemporary nations and states, we conduct a large-scale test of TL theory in 86 non-industrial societies. We show that tightness covaries across domains of social norms (e.g. socialization, law, gender) in these societies, suggesting that it is a domain-general facet of culture. We replicate many past findings from TL theory: tightness correlates positively with several ecological threats, including pathogen prevalence, population pressure, scarcity, and several forms of warfare. Finally, we provide evidence for several new predictions from TL theory. Tightness correlates positively with social complexity, authoritarian leadership, patrilocality, and negatively with contact between societies. These analyses replicate several nation-level and state-level findings while also uncovering new insights into human culture. We also provide metrics that can be used by future studies on cultural tightness in the ethnographic record.