Evolution and Human Behavior最新文献

The near totality of human mate choice research occurs in large-scale, urban, industrial populations. It is unclear to what extent lessons learned from such populations reflect generalizable features of human mating psychology as opposed to localized responses to the demands of these historically unusual environments. Here, we use couple simulation, an agent-based modeling technique, to compare models of mate choice across both a U.S. sample (n = 1678) and a sample of k = 15 couples from Conambo, Ecuador—a relatively remote community of horticultural-foragers in the Ecuadorian Amazon. The Conambo sample provides a unique opportunity to evaluate models of mate choice in that (1) this sample represents approximately 50% of the households within this community and (2) all of the participants in this sample are acquainted with one another. Participants in Conambo completed a ranking task in which each participant ranked each opposite-sex adult in the community in terms of their quality as a spouse. We used these rankings to simulate the mating market in Conambo under alternative models of mate choice. We find that these models are able to reproduce Conambo marriages at a high degree of accuracy and perform comparably across both the Conambo sample and U.S. samples. Specifically, the resource allocation model performs best in reproducing mate choices in both the U.S. and Conambo samples. These results suggest that at least some aspects of human mating psychology generalize across both large-scale industrialized and small-scale populations.

The proposal that humans possess an evolved psychology of ownership is a highly plausible one. But what, if any, features of human ownership psychology might be universal? Psychologists have proposed that human ownership psychology might contain rules or norms for determining ownership, some of which might be universal. Here we explore first mover norms, in which an individual who acts first or exerts higher initial effort towards an object is recognized as its owner. Developmental studies in North America and Europe have provided evidence that first mover intuitions, especially about first possession, reliably develop in childhood, and some cross-cultural studies have supported this. Ethnographic research, however, provides mixed evidence about the universality of first-mover norms across cultures and domains. Here we report results from an experimental study comparing judgments of Achuar adults in Ecuador with those of an online U.S. sample. Achuar judgments leaned weakly in favor of first possessors in the domain of hunted game, but not for land. For land, a principle of use took precedence over first possession. U.S. participants, on the other hand, exhibited strong first possessor intuitions across both domains, consistent with prior results in the psychological literature. Together these findings suggest that first mover norms for assigning ownership may be more culturally and contextually variable than prior psychological research has suggested.

Human societies depend on the ability of their members to coordinate and cooperate with others. Yet, within-group conflict can threaten group stability. This threat is severe among humans due to the scale of our societies and the frequent low levels of relatedness between members. Our ability to resolve inter-individual conflicts is a key aspect of our species' success. Despite the importance of conflict resolution in human sociality, the socio-ecology of how within-group conflicts are resolved in naturalistic settings is underexplored. Using a sample of 160 inter-individual conflicts reported by 81 adults from an agro-pastoralist community in southwest Ethiopia, we identify the primary causes of interpersonal conflict and the features associated with third-party mediation and conflict outcomes. We find that both men and women experience relatively severe inter- and intra-gender conflicts; conflicts between women are more likely to be social in nature, while conflicts between men are more likely to be over resource control. Third-party mediation more often occurs in social conflicts rather than conflicts over material or subsistence resources and in conflicts between clan members and friends. Mediators in conflicts between women tend to be women while mediators for conflicts between men tend to be men. Women, however, are as equally likely as men to help mediate inter-gender conflicts, which suggests an important opportunity for female leadership in this patriarchal society. Although more than 80% of conflicts were resolved, social conflicts are more difficult to resolve than conflicts over resources. Conflict severity, clan membership, and the relationship between those in conflict are associated with severed relationships. These results underscore the importance of third-party mediators and inter-gender interactions in human societies and the importance of socio-economic structures in shaping interpersonal conflicts and their resolution.

Politically egalitarian societies were likely more common in pre-history than in recent millenia. Why did societies become more hierarchical? Answers to this question remain debated, based on evidence largely drawn from archaeological case studies or comparison of societies from the ethnographic record. I suggest that modern small-scale societies transitioning to market economies can provide complementary tests of the sources of political inequality. I first describe moderate variation in men's influence during community meetings (i.e. political inequality) across four relatively egalitarian Tsimane villages in the Bolivian Amazon, as well as within one of these villages over twelve years. I then assess the roles of (1) sharing networks, (2) patron-client relationships, and (3) leadership opportunity in explaining that variation. Greater political inequality does not associate with reduced sharing but does associate with concentration of conflict mediation in the most influential men (per leadership opportunity) and more equivocally with intra-village paid labor (per patron-client models). In general, I argue that we need more micro-scale studies of societies in transition to understand why individuals come to tolerate greater political inequality.

Despite increasing evidence of non-kin contributions to cooperative childrearing, explicit investigation of non-kin allomaternal care remains rare, meaning we have little data to evaluate why non-kin provide care and whether non-kin investment translates into benefits for mothers or children. Here, we examine the role of godparents—kin and non-kin allomothers that often invest in both mothers and children—to investigate whether having a godparent translates into benefits in terms of the godchild's educational attainment. Among adults in two rural Bolivian communities, we find that having a godparent, whether kin or non-kin and regardless of where they live, does not predict years of education, finishing high school, or pursuing higher education. Instead, having more older siblings predicted educational attainment on all these dimensions. We make recommendations for how field researchers can better assess the impact of non-kin allomothers in future research.

Evolutionary theories of religion frequently assume that the presence of moralizing gods is positively associated with social complexity. An influential source of evidence for this assumption comes from researchers using the Standard Cross-Cultural Sample’s moralizing high gods variable as a proxy measure of their outcome of interest (the presence of moralizing gods). In this paper, we critically assess the common assumption that moralizing gods are associated with complex societies. We first discuss the high god variable’s coding criteria, which is defined by whether or not a god is the creator or director of the universe, regardless of power or omniscience. We then show that these criteria, which are not relevant to the question about whether gods are moralistic or punitive, has led researchers to underestimate the presence of moralizing gods by systematically producing false negatives – inferring that truly present moralizing gods are absent because moralizing high gods are absent. We then use datasets that include both moralizing gods and moralizing high gods to show that researchers risk inferring false negatives more frequently among lower levels of social complexity. As we also show, this likely leads to a spurious positive association between social complexity and the presence of moralizing gods. We then briefly discuss the ethnographic data and historical biases that might have strengthened this spurious association. We therefore question the widely assumed positive association between morally punitive gods and social complexity, and conclude that ethnographic evidence supports the prevalence of moralizing gods among small-scale societies.

Humans form and maintain friendships across long distances, which can provide access to non-local resources and support against large shocks that affect the entire local community. However, there may be a greater risk of defection in long-distance friendships, as monitoring for defection is more difficult at greater distances; accordingly, help between long-distance friends may be more explicitly contingent than between close-distance friends. We interviewed 918 participants from 21 fishing villages in Tanzania about whether they had received help in the form of a gift or loan from a friend living in their village and a friend living in a neighboring village. As there are local expectations that loans will be repaid but gifts will not, we predicted that close-distance friends would be more likely to help with gifts, whereas long-distance friends would be more likely to help with loans. Contrary to our predictions, gifts and loans between close- and long-distance friends were similar in kind and amount, though close-distance friends provided help more frequently, possibly because close-distance friends are more likely to meet frequently and belong to the same religious congregation. These results indicate that long-distance friendships are an important, and likely robust, strategy for managing risk and accessing more resources.

Fines, corporal punishments, and other procedures of punitive justice recur across small-scale societies. Although they are often assumed to enforce group norms, we here propose the relation-restoration hypothesis of punitive justice, according to which punitive procedures function to restore dyadic cooperation and curtail conflict between offender and victim following violations of reciprocal obligations. We test this hypothesis's predictions using observations of justice systems in three small-scale societies. We code ethnographic reports of 97 transgressions among Kiowa equestrian foragers (North America); analyze a sample of 302 transgressions among Mentawai horticulturalists (Indonesia); and review retributive procedures documented among Nuer pastoralists (South Sudan). Consistent with the relation-restoration hypothesis, we find that third-party punishment is rare; that most third-party involvement aims at resolving conflicts; that costs paid by offenders serve to achieve forgiveness by repairing victims; that punitive justice is accompanied by ceremonial procedures aimed at limiting conflict and restoring goodwill; and that failures to impose costs contribute to a decline in reciprocal cooperation. Although we document rare instances of third-party punishment among the Kiowa (6.6% of offenses), punitive justice more often serves as restorative justice, appeasing victims' urge for revenge while not overly harming offenders' interests to ensure reconciliation.