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Abstract Formal theoretical models propose that cooperative networks can be maintained when individuals condition behavior on social standing. Here, we empirically examine the predictions of such models of positive and negative indirect reciprocity using a suite of network-structured economic games in four rural Colombian communities (N i n d = 496 individuals, N o b s = 53,876 ratings/transfers). We observe that, at a dyadic-level, individuals have a strong tendency to exploit and punish others in bad standing (e.g., those perceived as selfish), and allocate resources to those in good standing (e.g., those perceived as generous). These dyadic findings scale to a more generalized, community level, where reputations for being generous are associated with receipt of allocations, and reputations for being selfish are associated with receipt of punishment. These empirical results illustrate the roles that both positive and negative reciprocity, and costly punishment, play in sustaining community-wide cooperation networks.

Abstract A key issue distinguishing prominent evolutionary models of human life history is whether prolonged childhood evolved to facilitate learning in a skill- and strength-intensive foraging niche requiring high levels of cooperation. Considering the diversity of environments humans inhabit, children’s activities should also reflect local social and ecological opportunities and constraints. To better understand our species’ developmental plasticity, the present paper compiled a time allocation dataset for children and adolescents from twelve hunter-gatherer and mixed-subsistence forager societies (n = 690; 3–18 years; 52% girls). We investigated how environmental factors, local ecological risk, and men and women’s relative energetic contributions were associated with cross-cultural variation in child and adolescent time allocation to childcare, food production, domestic work, and play. Annual precipitation, annual mean temperature, and net primary productivity were not strongly associated with child and adolescent activity budgets. Increased risk of encounters with dangerous animals and dehydration negatively predicted time allocation to childcare and domestic work, but not food production. Gender differences in child and adolescent activity budgets were stronger in societies where men made greater direct contributions to food production than women. We interpret these findings as suggesting that children and their caregivers adjust their activities to facilitate the early acquisition of knowledge which helps children safely cooperate with adults in a range of social and ecological environments. These findings compel us to consider how childhood may have also evolved to facilitate flexible participation in productive activities in early life.

Abstract The present pre-registered research provides the first evidence that a downwards head tilt is sufficient to communicate dominance from a neutral facial expression among the Mayangna, members of an unindustrialized, small-scale traditional society in Nicaragua who have had minimal exposure to North American culture. Consistent with the Action Unit imposter effect observed in North American populations (Witkower and Tracy in Psychol Sci 30:893–906, 2019), changes to the appearance of the upper face caused by a downwards head tilt were sufficient to elicit perceptions of dominance among this population. Given that the Mayangna are unlikely to associate a downwards head tilt or related apparent facial changes with dominance as a result of cross-cultural learning, the present results suggest that perceptions of dominance formed from a downwards head tilt, and the visual illusion shaping these perceptions, are a widely generalizable, and possibly universal, feature of human psychology.