Evolution and Human Behavior最新文献

We present a study testing the existence and correlates of personality concepts in the village of Conambo, Ecuador, which is home to horticultural-foragers located in the Sápara Territory of the Ecuadorian Amazon. Lexical terms to describe the three focal personality concepts from the HEXACO taxonomy—Sociability, Immodesty, and Un-emotionality—were interpreted from Spanish into the Indigenous languages of Achuar and Quichua. These terms were employed in a photo ranking task wherein 76 adult community members ranked the relative standing of same-sex others on each personality concept. Inter-ranker agreement was high for Sociability and Immodesty, but low for Un-emotionality. We tested the associations among individual differences in (i) Sociability and Immodesty, (ii) hierarchical status and fertility, which are hypothesized fitness-linked benefits of high Sociability and Immodesty, and (iii) physical strength, which is a hypothesized calibrator of status-oriented personality strategies. Using Bayesian models and psychological networks including age controls, we found good evidence that men's physical strength associated positively with Sociability, Immodesty, and status. Among both sexes, Sociability and Immodesty exhibited strong positive correlations with status, but evidence was weaker that the personality traits associated with fertility. Status associated positively with fertility among both sexes. We conclude that two personality concepts imported from the HEXACO and Big Five taxonomies, Sociability and Immodesty, exist with common meaning in the minds of Conambo villagers and appear adaptively patterned in relation to physical strength and fitness-linked outcomes. We argue that the photo ranking task employed in this research produces personality assessments with high validity and should therefore be adopted in future studies of individual differences in face-to-face groups.

Humans transmit cultural information to others in a variety of ways that can affect productivity, cultural success, and ultimately fitness. Not all potential transmitters are expected to be equally preferred by learners or equally willing to influence their culture acquisition. Across socioeconomic opportunities and ages in the human life course, costs and benefits to both learners and potential transmitters are expected to vary, affecting rates of culture transmission from different vectors. Here we examine reported patterns of culture transmission contributing to 92 essential skills among a sample of 421 Tsimane forager-farmers native to Bolivia. Consistent with the expectation that the costly provision of support and cultural information typically flows from older to younger generations in a subsistence society, we find that the development of essential knowledge and skills is primarily influenced by older same-sex relatives, especially parents. Grandparents are more often reported as transmitters for low-strength/high-difficulty skills that they have comparative advantage in, such as storytelling and musical performance. Though less frequent, same generation peers are more likely to provide discouragement in the learning process and to transmit modern, market-oriented skills. Our findings suggest that kinship, gender, generational seniority, and skill type together explain the vectors and styles of influence responsible for essential culture transmission. The multigenerational pedagogy documented here helps facilitate successful economic and social production in a complex skills niche dependent on multigenerational cooperation, such as observed in human hunter-gatherers and other subsistence populations.

Previous research argues that female choice may not be as powerful an influence on the evolution of human mating preferences as once expected given the importance of parental choice in marital practices across cultures. Furthermore, much of the literature supporting this argument assumes that endorsed cultural norms reported in the ethnographic record accurately represent individuals' behaviors. Here, we argue that the roles of parent-offspring conflict and parental choice are more nuanced. We test predictions from parent-offspring conflict theory and illuminate three loci of conflict between parents and daughters over partner choice. Using data from over 10 years of fieldwork in Shuar communities, we demonstrate that endorsed norms do not reflect complete behavioral repertoires at the individual level. We conclude that analyzing individual behavior provides insight into (1) areas of parental-offspring conflict and (2) complementary aspects of female choice and parental choice.

For most of human evolution, accumulated cultural knowledge has been stored in memory and transmitted orally. This presents a daunting information management problem: how to store and transmit this knowledge in a portable format that resists corruption. One solution–widespread among foragers–is to encode knowledge in narrative. However, this strategy depends on accurate performance of the story. Significantly, some forager cultures have rules regulating myth performance, although the extent of this phenomenon is unknown. We hypothesize that these rules subserve high-fidelity transmission across generations. Accordingly, we predicted that, across forager cultures, myth-telling rules will mandate: (P1) transmission by the most proficient storytellers (P2) under low-distraction conditions with (P3) multiple individuals and (P4) multiple generations present, and the application of measures that (P5) prevent, identify, and/or correct errors, (P6) maintain audience attention, (P7) discourage rule violations and/or (P8) incentivize rule compliance. To test these predictions, we searched the forager ethnographic record for descriptions of myth performance, and coded them for prescriptions/proscriptions regarding narrator age, performance context, audience composition, narrative delivery, and audience comportment, as well as sanctions associated with rule transgression or compliance. Results indicate that rules regulating myth performance are widespread across forager cultures, and are characterized by features that reduce the likelihood of copy errors. These findings help elucidate the role that anthropogenic ratchets played in the emergence of cumulative culture.

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.