Evolutionary Human Sciences最新文献

Religious celibate monks at the household level possibly reduce all-cause mortality risk among non-monk older Tibetans. This study aims to investigate the association between having a celibate monk in a family and the all-cause mortality of non-monk household members in a Tibetan population. Baseline interviews were conducted for 713 agropastoral Amdo Tibetans aged ≥50 years residing in the eastern Tibetan Plateau from 2016 to 2017. The Cox mixed-effects regression model was used to estimate the association between having a celibate monk in a household and the mortality risk of other non-monk household members. Potential confounders included age, sex, household size, educational attainment, household wealth (measured as the number of yaks), marital status, and annual expenditure. During a median follow-up of 7 years, 54 deaths were identified. The results showed that people living in households with celibate monks had a lower risk of all-cause mortality (hazard ratio: 0.31, 95% confidence interval: 0.14, 0.67) as compared with those living in households without celibate monks. The results remained robust after controlling for confounders, suggesting that religious celibate monks at the household level were associated with lower all-cause mortality among non-monk older household members.

Perception studies describe numerous discrete morphological facial features as important to judgements of various characteristics. Interestingly, little is known about whether people actually direct their visual attention to these features and how specific contexts or sex affect this attention. We, therefore, examined visual attention to faces in the context of intersexual (opposite-sex assessment of attractiveness) and intrasexual (same-sex assessment of dominance) selection. In total, 93 women and 33 men rated 80 high-resolution facial photographs of men and women while their gaze was recorded using eye-tracking. To explore patterns of raters' attention to faces and specific facial features, we used the number of fixations, fixation duration, and visit duration as visual attention measures. Women directed more visual attention towards the faces of potential partners (more fixations) than potential rivals, and men had longer fixation duration when assessing potential partners than rivals. Facial features that acquired the most visual attention across contexts and sexes were the eyes, nose, and mouth, but small differences between the sexes and contexts in visual attention were found for other facial regions suggested by previous perception studies, such as the chin and the cheeks indicating their importance in specific judgements.

Derived from the disease-avoidance model is the hypothesis that people may direct negative cognitive and behavioural responses towards individuals with physical disfiguring conditions, including physical disabilities. According to the behavioral immune system, physical disability-a non-contagious physical disfigurement-may falsely activate cognitive disease-avoidance processes, resulting in prejudicial or negative responses toward individuals with physical disabilities. For the first time this hypothesis is put to the test by investigating whether ratings of attractiveness and comfort for a social interaction vary systematically with physical disability (Studies 1 and 2). In addition, we tested whether these ratings were associated with individual differences in pathogen disgust and perceived vulnerability to disease. In Study 3 we overcame possible methodological limitations by employing a virtual reality (VR) environment. A fourth study was conducted to extend the first two studies by using a more diverse set of avatars. Results from Studies 1 and 2 indicated that disability did not significantly impact comfort ratings for social interactions, although non-disabled stimuli were rated as more attractive. However, Study 3 showed that in a VR environment, participants preferred closer proximity to non-disabled avatars over disabled ones, a preference not mitigated by the presence of prosthetics. Study 4 replicated these findings with varied 2D avatars, showing that disability significantly affected both comfort and attractiveness ratings, with non-disabled avatars rated highest, followed by those with prosthetics, and finally disabled avatars. Despite these findings, the expected relationship between comfort ratings and individual differences in pathogen disgust or perceived infectability did not emerge, challenging the behavioural immune system proposal. The discomfort associated with physical disability may be more related to social stigma or preconceived notions than to an innate disease-avoidance response.

Evolutionary scientists argue that prosociality has been central to human ecological success. Theoretical models and behavioural experiments have found that prosociality, and cooperation in particular, is conditional and context dependent, that individuals vary in their propensity to cooperate, and that reciprocity stabilizes these behaviours within groups. Experimental findings have had limited validation with observations of behaviour in natural settings, especially in organizational contexts. Here, we report in situ measurements of collective action, which show that reciprocity is abundant in organizations embedded in a cash economy. We study small 'food clubs', where members share bulk purchases and are considered to be heavily dependent on cooperation. We use high-resolution data on the economic interactions of 1,528 individuals across 35 clubs and over a combined 107 years of operation. We develop a network method to detect different directional and temporal forms of economic reciprocity, and statistically classify individual behavioural types akin to those in experiments. We find abundant direct reciprocity, supplemented by indirect reciprocity, and that members of most clubs can be identified as consistent reciprocators. This study provides initial observational evidence that economic reciprocity may be more abundant in real-world settings, sharpening the findings of the behavioural study of cooperation and contributing to the more naturalistic study of reciprocity and prosociality.

With the objective of informing theoretical accounts of social learning and gendered conflict, we explore the role of prestige in the formation of men's beliefs about gender in a semi-rural but fast urbanizing community in north-western Tanzania. Using focus groups and participant observation, we contrast the extent to which young men view elders and men from the neighbouring city as prestigious, and the beliefs they ascribe to each category. Elders were viewed as prestigious because of their age and position as preservers and teachers of societal norms. Their prestige was culturally mandated, as evidenced by customs bestowing respect. In contrast, only subcategories of city men were deemed prestigious dependent on individual achievement. Prestige was difficult to distinguish from dominance, as both elders and city men can exert penalties on those with differing views. Elders were viewed as mostly, but not always, unsupportive of women's empowerment, whereas city men were viewed as mostly, but not always, supportive of women's empowerment. We conclude that urbanization shifts the distribution of prestige, exposing individuals to novel sources of social influence. However, future studies should be wary not to oversimplify elders as upholders of patriarchal beliefs and city men as universally supportive of women's empowerment.

The suffixing bias (the tendency to exploit suffixes more often than prefixes to express grammatical meanings) in world's languages was identified a century ago, yet we still lack a clear account for why it emerged, namely, whether the bias emerged because general cognitive mechanisms shape languages to be more easily processed by available cognitive machinery, or the bias is speech-specific and is determined by domain-specific mechanisms. We used statistical learning (SL) experiments to compare processing of suffixed and prefixed sequences on linguistic and non-linguistic material. SL is not speech-specific, and we observed the suffixing preference only on linguistic material, suggesting its language-specific origin. Moreover, morphological properties of native languages (existence of grammatical prefixes) modulate suffixing preferences in SL experiments only on linguistic material, suggesting limited cross-domain transfer.

We review the methods we developed to study female genital cutting in Sudan and sex-selective abortion in Armenia. These methods were untested at the time of our original research, and here we compare the distinct but overlapping approaches we used to validate our methods for each of the two countries. Additionally, we repeat a number of analyses, including those related to validation, with previously unpublished data from Sudan. All results replicate previous findings. Replicating previous results is encouraging, but we nonetheless argue that validation for Armenia is more convincing than for Sudan. Specifically, even if female genital cutting and the preferential abortion of females are equally sensitive as research topics, son bias is inherently easier to study than cutting because biological sex determination is a random process with no natural analogue in the case of cutting. This randomness provides a kind of cover for research participants who are son-biased but want to create the impression that they are not. This cover, in turn, allows the researcher to resolve any trade-off between methods that produce explicit granular data and methods that produce untraceable, highly aggregated data in favour of methods producing the explicit and granular.

Survey results have shown that the traits women seek in a partner are different from the traits parents seek in a son-in-law. These differences have been attributed to parent-offspring conflict, where parents prefer mates for their offspring who provide benefits to the entire family group, but adult women prefer traits in a potential partner that indicate heritable fitness (e.g. creativity, exciting personality). We compare the characteristics of husbands of women in self-choice and arranged marriages using data from the longitudinal Indonesia Family Life Survey (IFLS) which surveyed families between 1993 and 2015. Results show that the husbands of women in arranged marriages had lower levels of completed education than those from self-choice marriages, counter to predictions. There were no significant differences in the husband's wealth prior to marriage or the proportion of couples who were of the same religion. An examination of personality traits showed little difference based on arranged marriage status. The only prediction that had significant support was that couples in arranged marriages were more likely to share an ethnic background than couples in self-choice marriages. These results suggest that the characteristics of husbands vary little by arranged versus self-choice marriage status, contrary to previous survey findings.

Striking a balance between individual and social learning is one of the key capabilities that support adaptation under uncertainty. Although intergenerational transmission of information is ubiquitous, little is known about when and how newcomers switch from learning loyally from preceding models to exploring independently. Using a behavioural experiment, we investigated how social information available from a preceding demonstrator affects the timing of becoming independent and individual performance thereafter. Participants worked on a 30-armed bandit task for 100 trials. For the first 15 trials, participants simply observed the choices of a demonstrator who had accumulated more knowledge about the environment and passively received rewards from the demonstrator's choices. Thereafter, participants could switch to making independent choices at any time. We had three conditions differing in the social information available from the demonstrator: choice only, reward only or both. Results showed that both participants' strategies about when to stop observational learning and their behavioural patterns after independence depended on the available social information. Participants generally failed to make the best use of previously observed social information in their subsequent independent choices, suggesting the importance of direct communication beyond passive observation for better intergenerational transmission under uncertainty. Implications for cultural evolution are discussed.