Search

Focusing on clothing and adornment (dress), this worldwide cross-cultural comparison asks why people in some societies appear to dress in uniform or standardized ways, whereas in other societies individuals display considerable variability in dress. The broader research question is why some societies have more within-group variation than others. Hypotheses are tested on 80 societies drawn from the Standard Cross-Cultural Sample (SCCS). The central hypotheses consider the impact of general societal tightness or looseness, degree of egalitarianism as well as other aspects of societal complexity, and the role of resource stress on dress standardization. Exploratory methods identify four latent constructs of dress from newly coded variables, one latent construct for tightness/looseness, and one latent construct for resource stress. As expected, (1) increased societal tightness was positively related to increased standardization and rules regarding dress and (2) increased resource stress is generally related to more standardization of dress and rules regarding adornment. However, contrary to theoretical expectations, the predictors of tightness–looseness differ from the predictors of dress. Most importantly, resource stress negatively predicts tightness but positively predicts three of the latent dress constructs. The relationship between dress standardization and societal complexity may be curvilinear, with mid-range societies having more standardization. Although some of the theorized relationships are supported (including that standardization of dress is predicted by societal tightness and more resource stress), at the end of paper we discuss some puzzling findings, speculate about possible explanations, and suggest further lines of research. [ABSTRACT FROM AUTHOR]

Together with language, music is perhaps the most distinctive behavioral trait of the human species. Different hypotheses have been proposed to explain why only humans perform music and how this ability might have evolved in our species. In this paper, we advance a new model of music evolution that builds on the self-domestication view of human evolution, according to which the human phenotype is, at least in part, the outcome of a process similar to domestication in other mammals, triggered by the reduction in reactive aggression responses to environmental changes. We specifically argue that self-domestication can account for some of the cognitive changes, and particularly for the behaviors conducive to the complexification of music through a cultural mechanism. We hypothesize four stages in the evolution of music under self-domestication forces: (1) collective protomusic; (2) private, timbre-oriented music; (3) small-group, pitch-oriented music; and (4) collective, tonally organized music. This line of development encompasses the worldwide diversity of music types and genres and parallels what has been hypothesized for languages. Overall, music diversity might have emerged in a gradual fashion under the effects of the enhanced cultural niche construction as shaped by the progressive decrease in reactive (i.e., impulsive, triggered by fear or anger) aggression and the increase in proactive (i.e., premeditated, goal-directed) aggression. [ABSTRACT FROM AUTHOR]

How is word meaning established, and how do individuals acquire it? What ensures the uniform understanding of word meaning in a linguistic community? In this paper I draw from cultural attraction theory and use folk biology as an example domain and address these questions by treating meaning acquisition as an inferential process. I show that significant variation exists in how individuals understand the meaning of inclusive biological labels such as "plant" and "animal" due to variation in their salience in contemporary ethnic minority groups in southwest China, and I present historical textual evidence that the meaning of inclusive terms is often unstable but can be sustained by such cultural institutions as religion and education, which provide situations in which the meaning of linguistic labels can be unambiguously inferred. [ABSTRACT FROM AUTHOR]

Chance-based gambling has been a recurrent cultural activity throughout history and across many diverse human societies. In this paper, I combine quantitative and qualitative data and present a cultural evolutionary framework to explain why the odds in games of chance in premodern China appeared "designed" to ensure a moderate yet favorable house advantage. This is especially intriguing since extensive research in the history of probability has shown that, prior to the development of probability theory, people had very limited understanding of the nature of random events and were generally disinclined to think mathematically about the frequency of their occurrence. I argue that games of chance in the context of gambling may have culturally evolved into their documented forms via a process of selective imitation and retention, and neither the customers nor the gambling houses understood the probability calculus involved in these games. [ABSTRACT FROM AUTHOR]

Humans have a complex and dynamic mating system, and there is evidence that our modern sexual preferences stem from evolutionary pressures. In the current paper we explore male use of a dual mating strategy: simultaneously pursuing both a long-term relationship (pair-bonding) as well as short-term, extra-pair copulations (variety-seeking). The primary constraint on such sexual pursuits is partner preferences, which can limit male behavior and hence cloud inferences about male preferences. The aim of this study was to investigate heterosexual male mating preferences when largely unconstrained by female partner preferences. In service of this goal, female full-service sex workers (N = 6) were surveyed on the traits and behaviors of their male clients (N = 516) and iterative cluster analysis was used to identify male mating typologies. Two clusters emerged: clients seeking a pair-bonding experience and clients seeking a variety experience. Results also suggested that romantically committed men were more likely to seek a variety experience than a relationship experience. We conclude that men desire both pair-bonding and sexual variety, and that their preference for one might be predicted by fulfilment of the other. These findings have implications for relationships, providing insight into motivations for male infidelity. [ABSTRACT FROM AUTHOR]

Tinbergen's classic "On Aims and Methods of Ethology" (Zeitschrift für Tierpsychologie, 20, 1963) proposed four levels of explanation of behavior, which he thought would soon apply to humans. This paper discusses the need for multilevel explanation; Huxley and Mayr's prior models, and others that followed; Tinbergen's differences with Lorenz on "the innate"; and Mayr's ultimate/proximate distinction. It synthesizes these approaches with nine levels of explanation in three categories: phylogeny, natural selection, and genomics (ultimate causes); maturation, sensitive period effects, and routine environmental effects (intermediate causes); and hormonal/metabolic processes, neural circuitry, and eliciting stimuli (proximate causes), as a respectful extension of Tinbergen's levels. The proposed classification supports and builds on Tinbergen's multilevel model and Mayr's ultimate/proximate continuum, adding intermediate causes in accord with Tinbergen's emphasis on ontogeny. It requires no modification of Standard Evolutionary Theory or The Modern Synthesis, but shows that much that critics claim was missing was in fact part of Neo-Darwinian theory (so named by J. Mark Baldwin in The American Naturalist in 1896) all along, notably reciprocal causation in ontogeny, niche construction, cultural evolution, and multilevel selection. Updates of classical examples in ethology are offered at each of the nine levels, including the neuroethological and genomic findings Tinbergen foresaw. Finally, human examples are supplied at each level, fulfilling his hope of human applications as part of the biology of behavior. This broad ethological framework empowers us to explain human behavior—eventually completely—and vindicates the idea of human nature, and of humans as a part of nature. [ABSTRACT FROM AUTHOR]

Sex ratios have widely been recognized as an important link between demographic contexts and behavior because changes in the ratio shift sex-specific bargaining power in the partner market. Implicitly, the literature considers individual partner market experiences to be a function of local sex ratios. However, empirical evidence on the correspondence between subjective partner availability and local sex ratios is lacking so far. In this paper, we analyzed how closely a set of different local sex ratio measures correlates with subjective partner market experiences. Linking a longitudinal German survey to population data for different entities (states, counties, municipalities), we used multilevel logistic regression models to explore associations between singles' subjective partner market experiences and various operationalizations of local sex ratios. Results suggest that local sex ratios correlated only weakly with subjective partner market experiences. Adult sex ratios based on broad age brackets, including those for lower-level entities, did not significantly predict whether individuals predominantly met individuals of their own sex. More fine-grained, age-specific sex ratios prove to be better predictors of subjective partner market experiences, in particular when age hypergamy patterns were incorporated. Nevertheless, the respective associations were only significant for selected measures. In a complementary analysis, we illustrate the validity of the subjective indicator as a predictor of relationship formation. In sum, our results suggest that subjective partner availability is not adequately represented by the broad adult sex ratio measures that are frequently used in the literature. Future research should be careful not to equate local sex ratios and conscious partner market experiences. [ABSTRACT FROM AUTHOR]

This paper examines how innovative skills and knowledge are transmitted and acquired among adolescents in two hunter-gatherer communities, the Aka of southern Central African Republic and the Chabu of southwestern Ethiopia. Modes of transmission and processes of social learning are addressed. Innovation as well as social learning have been hypothesized to be key features of human cumulative culture, enhancing the fitness and survival of individuals in diverse environments. The innovation literature indicates adult males are more innovative than children and female adults and therefore predicts that adolescents will seek out adult males. Further, the mode of transmission should be oblique (i.e., learning from adults other than parents). Thus, learning of innovations should be oblique or horizontal rather than vertical, with adolescents paying particular attention to "successful" innovative individuals (prestige bias). The social learning literature indicates that complex skills or knowledge is likely to be learned through teaching, and therefore that teaching will be an important process in the transmission of innovations. In-depth and semi-structured interviews, informal observations, and systematic free-listing were used to evaluate these hypotheses. The study found that (1) cultural context patterned whether or not adolescents sought out adult male or female innovators; (2) oblique modes of transmission were mentioned with greater frequency than horizontal or vertical modes; (3) knowledge and skill bias was notable and explicitly linked by the adolescents to reproductive effort; and (4) teaching was biased toward same-sex individuals and was an important but not an exclusive means of transmitting complex skills and social knowledge. [ABSTRACT FROM AUTHOR]

Copyright of Human Nature is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Human fascination with art has deep evolutionary roots, yet its role remains a puzzle for evolutionary theory. Although its widespread presence across cultures suggests a potential adaptive function, determining its evolutionary origins requires more comprehensive evidence beyond mere universality or assumed survival benefits. This paper introduces and tests the Collector Hypothesis, which suggests that artworks serve as indicators of collectors’ surplus wealth and social status, offering greater benefits to collectors than to artists in mating and reproductive contexts. Our study among Indigenous Papuan communities provides preliminary support for the Collector Hypothesis, indicating that, compared to artists, collectors are perceived as having higher social status and greater attractiveness to women. These findings provide unique insights into Papuan communities and contribute to the ongoing discussion about art’s adaptive significance of art by suggesting that artistic capacities may benefit not only creators but also those who accumulate and display art. Further research in diverse cultural contexts is needed for a comprehensive understanding of this interplay. [ABSTRACT FROM AUTHOR]

Evolutionary theory predicts that social status and fertility will be positively related. It also predicts that the relationship between status and fertility will differ for men and women. This is particularly likely in modern societies given evidence that females face greater trade-offs between status and resource acquisition and fertility than males. This paper tests these hypotheses using newly released data from the 2014 wave of the Survey of Income and Program Participation by the US Census, which has the first complete measures of fertility and number of childbearing partners for a large, representative, national probability sample of men and women and also contains comprehensive measures of economic status as measured by personal and family resources, including income from all sources and all assets. Multivariate analyses show that personal income is positively associated with total fertility and number of childbearing unions for men only. For men, personal net worth is positively associated with number of childbearing unions; it is also positively associated with fertility for married men with a spouse present. These findings support evolutionary predictions of a positive relationship between status, access to mates, and reproductive success for males. Whereas personal income and personal net worth are negatively associated with total fertility and number of childbearing unions for women, family income (net of personal income) is positively associated with total fertility for women. For married men living with a spouse, family income (net of personal income) is negatively associated with total fertility. These findings are consistent with evolutionary theory given the existence of greater trade-offs between production and reproduction for women in an advanced industrial society. For women and men, family net worth (net of personal net worth) is negatively associated with number of childbearing unions and fertility. Implications are discussed. [ABSTRACT FROM AUTHOR]

The Seville Statement on Violence rejected the view that violence and war were in any way rooted in human nature and proclaimed that they were merely a cultural artifact. This paper points out both the valid and invalid parts of the statement. It concludes that the potential for both war and peace is embedded in us. The human behavioral toolkit comprises a number of major tools, respectively geared for violent conflict, peaceful competition, or cooperation, depending on people's assessment of what will serve them best in any given circumstance. Conflict is only one tool—the hammer—in our diverse behavioral toolkit. However, all three behavioral strategies are not purely learned cultural forms. This naive nature/nurture dichotomy overlooks the heavy and complex biological machinery that is necessary for the working of each of them and the interplay between them. They are all very close under our skin and readily activated because they have all been very handy during our long evolutionary past. At the same time, they are variably calibrated to particular conditions through social learning, which means that their relative use may fluctuate widely. Thus, state authority has tilted the menu of human choices in the direction of the peaceful options in the domestic arena, and changing economic, social, and political conditions may be generating a similar effect in the international arena. [ABSTRACT FROM AUTHOR]

There has been a long-standing debate about the roles of San in the militaries of southern Africa and the prevalence of violence among the Ju/'hoansi and other San people. The evolutionary anthropology and social anthropological debates over the contexts in which violence and warfare occurs among hunters and gatherers are considered, as is the "tribal zone theory" of warfare between states and indigenous people. This paper assesses the issues that arise from these discussions, drawing on data from San in Angola, Namibia, Botswana, and Zimbabwe. Utilizing cases of how San have been affected by military forces and wildlife conservation agencies in what became protected areas in southern Africa, this article shows that indigenous peoples have been treated differentially by state and nongovernmental organizations involved in anti-poaching, shoot-to-kill, and forced resettlement policies. Particular emphasis is placed on the !Xun and Khwe San of southern Angola and northern Namibia and the Tshwa San of western Zimbabwe and northern Botswana, who have been impacted by militarization and coercive conservation efforts since the late nineteenth century. Principal conclusions are that conservation and militarization efforts have led to a reduction in land and resources available to indigenous people, higher levels of poverty, increased socioeconomic stratification, and lower levels of physical well-being. San have responded to these trends by engaging in social activism, forming community-based institutions, and pursuing legal actions aimed at obtaining human rights and equitable treatment. [ABSTRACT FROM AUTHOR]

In this paper I propose an evolutionary model of human status that expands upon an earlier model proposed by Henrich and Gil-White Evolution and Human Behavior, 22,165-196 (). According to their model, there are two systems of status attainment in humans-'two ways to the top': the dominance route, which involves physical intimidation, a psychology of fear and hubristic pride, and provides coercive power, and the prestige route, which involves skills and knowledge (competence), a psychology of attraction to experts and authentic pride, and translates mainly into influence. The two systems would have evolved in response to different selective pressures, with attraction to experts serving a social learning function and coinciding with the evolution of cumulative culture. In this paper I argue that (1) the only one way to the top is competence because dominance itself involves competence and confers prestige, so there is no such thing as pure dominance status; (2) dominance in primates has two components: a competitive one involving physical coercion and a cooperative one involving competence-based attraction to high-ranking individuals (proto-prestige); (3) competence grants the same general type of power ( dependence-based) in humans and other primates; (4) the attractiveness of high rank in primates is homologous with the admiration of experts in humans; (5) upon the evolution of cumulative culture, the attractiveness of high rank was co-opted to generate status differentials in a vast number of culturally generated domains of activity. I also discuss, in this perspective, the origins of hubristic pride, authentic pride, and nonauthoritarian leadership. [ABSTRACT FROM AUTHOR]

A correction to this paper has been published: https://doi.org/10.1007/s12110-021-09403-x [ABSTRACT FROM AUTHOR]

In this paper, the structure of a southeastern Spanish population was studied for the first time with respect to its inbreeding patterns and its relationship with demographic and geographic factors. Data on consanguineous marriages (up to second cousins) from 1900 to 1969 were taken from ecclesiastic dispensations. Our results confirm that the patterns and trends of inbreeding in the study area are consistent with those previously observed in most non-Cantabrian Spanish populations. The rate of consanguineous marriages was apparently stable between 1900 and 1935 and then sharply decreased since 1940, which coincides with industrialization in Spain. A marked departure from Hardy-Weinberg expectations (0.25) in the ratio of first cousin (M22) to second cousin (M33) marriages in the study population (0.88) was observed. The high levels of endogamy (>80%) and its significant steadiness throughout the twentieth century is noteworthy. Accordingly, our results show that exogamous marriages were not only poorly represented but also that this reduced mobility (<6 km) suggests that the choice of a mate was preferentially local. We found higher mobility in M22 with respect to M33 cousin mating. The relationships between population size and consanguinity rates and inbreeding fit power-law distributions. A significant positive correlation was observed between inbreeding and elevation. Many Spanish populations have experienced a prolonged and considerable isolation across generations, which has led to high proportions of historical and local endogamy that is associated, in general, with high F¯ values. Thus, assessing genomic inbreeding using runs of homozygosity (ROH) in current Spanish populations could be an additional pertinent strategy for obtaining a more refined perspective regarding the population history inferred from the extent and frequency of ROH regions. [ABSTRACT FROM AUTHOR]

Human sleeping arrangements have evolved over time and differ across cultures. The majority of adults share their bed at one time or another with a partner or child, and many also sleep with pets. In fact, around half of dog and cat owners report sharing a bed or bedroom with their pet(s). However, interspecies co-sleeping has been trivialized in the literature relative to interpersonal or human-human co-sleeping, receiving little attention from an interdisciplinary psychological perspective. In this paper, we provide a historical outline of the 'civilizing process' that has led to current sociocultural conceptions of sleep as an individual, private function crucial for the functioning of society and the health of individuals. We identify similar historical processes at work in the formation of contemporary constructions of socially normative sleeping arrangements for humans and animals. Importantly, since previous examinations of co-sleeping practices have anthropocentrically framed this topic, the result is an incomplete understanding of co-sleeping practices. By using dogs as an exemplar of human-animal co-sleeping, and comparing human-canine sleeping with adult-child co-sleeping, we determine that both forms of co-sleeping share common factors for establishment and maintenance, and often result in similar benefits and drawbacks. We propose that human-animal and adult-child co-sleeping should be approached as legitimate and socially relevant forms of co-sleeping, and we recommend that co-sleeping be approached broadly as a social practice involving relations with humans and other animals. Because our proposition is speculative and derived from canine-centric data, we recommend ongoing theoretical refinement grounded in empirical research addressing co-sleeping between humans and multiple animal species. [ABSTRACT FROM AUTHOR]

Anthropologists have long been interested in the reasons humans choose to help some individuals and not others. Early research considered psychological mediators, such as feelings of cohesion or closeness, but more recent work, largely in the tradition of human behavioral ecology, shifted attention away from psychological measures to clearer observables, such as past behavior, genetic relatedness, affinal ties, and geographic proximity. In this paper, we assess the value of reintegrating psychological measures-perceived social closeness-into the anthropological study of altruism. Specifically, analyzing social network data from four communities in rural Bangladesh ( N = 516), we show that perceived closeness has a strong independent effect on helping, which cannot be accounted for by other factors. These results illustrate the potential value of reintegrating proximate psychological measures into anthropological studies of human cooperation. [ABSTRACT FROM AUTHOR]

It has previously been suggested that the historically and geographically widespread persistence of religious beliefs occurs because it is a by-product of normal cognitive processes, ones which first evolved to confer survival advantages in the social domain. If this theory holds, then it is likely that inter-individual variation in the same biases may predict corresponding variation in religious thoughts and behaviors. Using an online questionnaire, 298 participants answered questions regarding their tendency to detect agency, the degree to which they displayed schizotypal traits, their ability to understand the emotions and motivations of others ('mentalizing'), and their religious beliefs and behaviors. Path analysis suggests that mentalizing, agency detection, and schizotypal thinking were each independently related to religiosity. Furthermore, schizotypal thinking and agency detection were highly interrelated with one another, whereas mentalizing was not. Although the degree to which an individual engages with religious or spiritual beliefs will be influenced by their cultural and historical context, this paper helps to elucidate the interplay between various cognitive processes that might predispose some individuals but not others toward holding such beliefs in the first place. [ABSTRACT FROM AUTHOR]

The hypothesis that father absence during childhood, as well as other forms of childhood psychosocial stress, might influence the timing of sexual maturity and adult reproductive behaviors has been the focus of considerable research. However, the majority of studies that have examined this prediction have used samples of women of European descent living in industrialized, low-fertility nations. This paper tests the father-absence hypothesis using the Cape Area Panel Study (CAPS), which samples young adults in Cape Town, South Africa. The sample contains multiple racial groups (blacks, coloureds [mixed race], and whites) and includes both males and females. Dependent variables include age at menarche, age at first sexual intercourse, and age at first pregnancy. Childhood stress is measured by father absence by age six (either never lived with father or lived with father some but not all years) and an index of childhood exposure to violence (measuring threatened or actual verbal or physical abuse). The hypothesis received no support for effect on age at menarche but was supported for age at first sex and first pregnancy. The model showed stronger support for coloureds and whites than blacks and had no predictive power at all for black males. [ABSTRACT FROM AUTHOR]

Relatives play an important role in human reproduction according to evolutionary theories of reproductive behavior, but previous empirical studies show large differences in the effects of kin on fertility outcomes. In our paper we examine the effect of co-resident kin and non-kin on the length of birth intervals over the reproductive life course of Dutch women born between 1842 and 1920. We estimate Cox proportional hazard models for parity progression based on the presence of kin and non-kin in the household while controlling for a large number of individual and community-level characteristics. We find that couples living with their brothers experienced shorter birth intervals whereas couples residing with a widowed father had relatively longer birth intervals. The effects of these types of kin on reproduction were most pronounced up to the birth of the fifth child, but not thereafter. We found no effect for mothers or other types of kin. [ABSTRACT FROM AUTHOR]

This special issue of Human Nature presents selected works from the 2015 and 2017 "Warfare, Environment, Social Inequality, and Pro-Sociability" (WESIPS) conferences held at the Center for Cross-Cultural Study in Seville, Spain. These investigations explore the manifestations of indigenous warfare and violence from a host of theoretical perspectives. Topics range from the origins of warfare to the psychological repercussions of combat, the relationship between warfare and status, as well as the documentation of peace processes among warring groups. This issue also examines the effects of militarization and coercive conservation on indigenous peoples. [ABSTRACT FROM AUTHOR]

Income inequality has been empirically linked to interpersonal competition and risk-taking behaviors, but a separate line of findings consistently shows that individuals have inaccurate perceptions of the actual levels of income inequality in society. How can inequality be both consistently misperceived and yet a reliable predictor of behavior? The present study extends both these lines of research by evaluating if the scope of input used to assess income inequality (i.e., at the national, state, county, or postal code level) can account for perception discrepancies and if actual/perceived inequality is associated with female intrasexual competition. Female participants recruited online from the general US population (n = 691) provided demographic information, measures of perceived income inequality, and measures of intrasexual competition attitudes and behavior. Actual and perceived income inequality (at any level) did not predict negative attitudes toward other women or female weighting of physical appearance as a desirable trait. Perceived income inequality and actual county-level inequality was, however, predictive of female competition in the form of self-sexualization clothing choice. Further analyses found that age and importance placed on physical attractiveness also predicted women's clothing choices. Perceptions of income inequality were predicted not by actual Gini indices, but by beliefs about the levels of poverty and income gaps. These results highlight the importance of better understanding the proximate cues by which people perceive environmental features such as inequality, and how those cues are used to adjust interpersonal behaviors. [ABSTRACT FROM AUTHOR]

Raymond Kelly's widely cited Warless Societies and the Origin of War (University of Michigan Press, 2000) seeks to explain the origins of two central signatures of human society: war and segmented—i.e., multilevel—societies. Both, he argues, arose with the emergence of a social-substitutability principle, a rule that establishes a collective identity among a set of individuals such that any one member becomes equivalent to, and responsible for the actions of, the others. This principle emerged during the Holocene, when population increase gave rise to the first lethal ambushes. By its nature, ambush obscures attackers' identities. Those attempting to retaliate for the ambush were therefore obliged to target members of the ambushers' group indiscriminately—i.e., based on a social-substitutability principle. Kelly's proposals draw welcome attention to a widespread, deeply influential, and unsettling human behavior, the disposition to hold everyone in a group culpable for the actions of a few, a proclivity that all too often results in mass slaughter. His general argument, however, is logically and empirically deficient, and cross-cultural evidence on ambush in contact-era New Guinea undermines his anonymity-of-ambush hypothesis. What then accounts for war and multilevel society? The New Guinea evidence strongly supports a contention that social-substitutability behavior arose not from offensive military action (i.e., ambush) but from the defensive military response to ambush. These findings render the social-substitutability argument's unconventional definition of war superfluous, undermine its chronology for the emergence of war, and underwrite an alternative scenario for the origins of multilevel, segmented society. [ABSTRACT FROM AUTHOR]

Humans share with other mammals and primates many social motivations and emotions, but they are also much more cooperative than even their closest primate relatives. Here I review recent comparative experiments and analyses that illustrate humans' species-typical social motivations and emotions for cooperation in comparison with those of other great apes. These may be classified most generally as (i) 'you > me' (e.g., prosocial sympathy, informative and pedagogical motives in communication); (ii) 'you = me' (e.g., feelings of mutual respect, fairness, resentment); (iii) 'we > me' (e.g., feelings of obligation and guilt); and (iv) 'WE (in the group) > me' (e.g., in-group loyalty and conformity to norms, shame, and many in-group biases). The existence of these species-typical and species-universal motivations and emotions provides compelling evidence for the importance of cooperative activities in the human species. [ABSTRACT FROM AUTHOR]

It has been theorized that the contagion of behaviors may be related to social cognitive abilities, but empirical findings are inconsistent. We recorded young adults' behavioral expression of contagious yawning and contagious smiling to video stimuli and employed a multi-method assessment of sociocognitive abilities including self-reported internal experience of emotional contagion, self-reported trait empathy, accuracy on a theory of mind task, and observed helping behavior. Results revealed that contagious yawners reported increases in tiredness from pre- to post-video stimuli exposure, providing support for the internal experience of emotional contagion, and were more likely to provide help to the experimenter relative to non-contagious yawners. Contagious smilers showed stably high levels of self-reported happiness from pre- to post-video exposure, were more likely to provide help to the experimenter, and had increased accuracy on a theory of mind task relative to non-contagious smilers. There were no differences in self-reported trait empathy for contagious versus non-contagious yawners or smilers. Contagious yawning may be related to some basic (i.e., emotional contagion) and advanced (i.e., helping behavior) sociocognitive processes, whereas contagious smiling is related to some advanced sociocognitive processes (i.e., theory of mind and helping behavior). [ABSTRACT FROM AUTHOR]

A Correction to this paper has been published: https://doi.org/10.1007/s12110-021-09399-4 [ABSTRACT FROM AUTHOR]

The amygdala is a hub in brain networks that supports social life and fear processing. Compared with other apes, humans have a relatively larger lateral nucleus of the amygdala, which is consistent with both the self-domestication and the cooperative breeding hypotheses of human evolution. Here, we take a comparative approach to the evolutionary origin of the relatively larger lateral amygdala nucleus in humans. We carry out phylogenetic analysis on a sample of 17 mammalian species for which we acquired single amygdala nuclei volumetric data. Our results indicate that there has been convergent evolution toward larger lateral amygdala nuclei in both domesticated and cooperatively breeding mammals. These results suggest that changes in processing fearful stimuli to reduce fear-induced aggression, which are necessary for domesticated and cooperatively breeding species alike, tap into the same neurobiological proximate mechanism. However, humans show changes not only in processing fearful stimuli but also in proactive prosociality. Since cooperative breeding, but not domestication, is also associated with increased proactive prosociality, a prominent role of the former during human evolution is more parsimonious, whereas self-domestication may have been involved as an additional stepping stone. [ABSTRACT FROM AUTHOR]

Population dynamics form a crucial component of human narratives in the past. Population responses and adaptations not only tell us about the human past but also offer insights into the present and future. Though an area of substantial interest, it is also one of often limited evidence. As such, traditional techniques from demography and anthropology must be adapted considerably to accommodate the available archaeological and ethnohistoric data and an appropriate inferential framework must be applied. In this article, I propose a ground-up, multidisciplinary approach to the study of past population dynamics. Specifically, I develop an empirically informed path diagram based on modern fertility interactions and sources of past environmental, sociocultural, and biological evidence to guide high-resolution case studies. The proposed approach is dynamic and can evolve in response to data inputs as case studies are undertaken. In application, this approach will create new knowledge of past population processes which can greatly enhance our presently limited knowledge of high-frequency, small-scale demographic fluctuations, as well as contribute to our broader understanding of significant population disturbances and change throughout human history. [ABSTRACT FROM AUTHOR]

Alloparenting, wherein people provide care to children who are not their biological offspring, is a key aspect of human child-rearing. In the Pacific, many children are adopted or fostered by custodial alloparents even when both biological parents are still alive. From a behavioral ecology perspective, such behaviors are puzzling: why parent someone else's child at your expense? Furthermore, little is known about how these arrangements are made in Pacific Islander societies today, who provides care, and what kinds of outcomes fostered children experience. A better understanding of these proximate factors may help reveal the ultimate drivers behind custodial alloparenting. Here, we report findings from a survey carried out with the caregivers of 282 children in rural areas of Vanuatu, an island nation in Melanesia. Most fostered and adopted children lived with relatives such as aunts, uncles, and grandparents (87.5%) rather than unrelated caregivers, with a strong preference for maternal kin. The most common reasons for these arrangements were that the parents had separated (16.7%), were engaging in labor migration (27.1%), or a combination of both (27.1%). Results for investment in children's education and their educational outcomes were mixed, although children removed from crisis situations did more poorly than children removed for aspirational reasons. Our findings suggest that custodial alloparenting helps families adapt to socioeconomic transitions and changing marriage practices. Outcomes may depend on a range of factors, such as the reason children were transferred out of the natal home to begin with. [ABSTRACT FROM AUTHOR]

This paper investigates relationships between men's testosterone and family life in a sample of approximately 350 Jamaican fathers of children 18-24 months of age. The study recognizes the role of testosterone as a proximate mechanism coordinating and reflecting male life history allocations within specific family and cultural contexts. A sample of Jamaican fathers and/or father figures reported to an assessment center for an interview based on a standardized questionnaire and provided a saliva sample for measuring testosterone level. Outcomes measured include subject demographics such as age and relationship status as well as partnership quality and sexuality and paternal attitudes and behavior. The variation in these fathers' relationship status (e.g., married co-residential fathers, fathers in new non-residential relationships) was not associated with men's testosterone. Too few stepfathers participated to enable a direct test of the prediction that stepfathers would have higher testosterone than biological fathers, although fathers who reported living with partners' (but not his own) children did not have higher testosterone than fathers not reporting residing with a non-biological child. Fathers' relationship quality was negatively related to their testosterone. Measures of paternal attitudes and behavior were not related to fathers' testosterone. Consistent with previous ethnography, this sample of Jamaican fathers exhibited variable life history profiles, including residential status. We discuss why fathers' relationship quality was found to be negatively related to their testosterone level, but other predictions were not upheld. [ABSTRACT FROM AUTHOR]

The Shodagor of Matlab, Bangladesh, are a seminomadic community of people who live and work on small wooden boats, within the extensive system of rivers and canals that traverse the country. This unique ecology places particular constraints on family and economic life and leads to Shodagor parents employing one of four distinct strategies to balance childcare and provisioning needs. The purpose of this paper is to understand the conditions that lead a family to choose one strategy over another by testing predictions about socioecological factors that impact the sexual division of labor, including a family's stage in the domestic cycle, aspects of the local ecology, and the availability of alloparents. Results show that although each factor has an impact on the division of labor individually, a confluence of these factors best explains within-group, between-family differences in how mothers and fathers divide subsistence and childcare labor. These factors also interact in particular ways for Shodagor families, and it appears that families choose their economic strategies based on the constellation of constraints that they face. The results of these analyses have implications for theory regarding the sexual division of labor across cultures and inform how Shodagor family economic and parenting strategies should be contextualized in future studies. [ABSTRACT FROM AUTHOR]

The establishment of a legal father for children of unmarried parents reflects both high paternity confidence and male willingness to commit to paternal investment. Whether an unmarried man voluntarily acknowledges paternity after a child is born has important consequences for both the mother and child. This paper brings to bear a life history perspective on paternity establishment, noting that men face trade-offs between mating and parental effort and that women will adjust their investment in children based on expected male investment. I predict that paternity establishment will be more likely when the mother has high socioeconomic status, when maternal health is good, and when the child is male, low parity, or a singleton (versus multiple) birth. I further predict that establishment of paternity will be associated with increased maternal investment in offspring, resulting in healthier babies with higher birthweights who are more likely to be breastfed. These predictions are tested using data on 5.4 million births in the United States from 2009 through 2013. Overall the results are consistent with the hypothesis that the trade-offs men face between reproductive and parental investment influence whether men voluntarily acknowledge paternity when a child is born. [ABSTRACT FROM AUTHOR]

Breastfeeding is one important form of maternal investment that is influenced by support from kin and non-kin. This paper investigates who provides support for breastfeeding mothers and their children, what type of support they provide, and how support impacts breastfeeding duration. The data were derived from a survey of 594 American mothers and were analyzed using quantitative methods, including Cox regression. Analyses indicate that mothers receive significant support, particularly from spouses and maternal grandmothers. More frequent breastfeeding discussions with La Leche League and maternal grandfathers were associated with longer duration, whereas discussions with physicians were associated with shorter breastfeeding duration. Results indicate that consulting others specifically about breastfeeding may influence breastfeeding decisions. The results are consistent with the idea that social support may influence breastfeeding duration and that some types of support are more influential than others. Furthermore, support persons should be educated about breastfeeding to prevent early weaning. [ABSTRACT FROM AUTHOR]

Independent of ecology, subsistence strategy, social complexity, or other aspects of socioecology, the altricial nature of young humans requires mothers to have help raising their offspring. What seems to be context-dependent, however, is who the helpers are, how they invest, and what the impacts of that investment are. In a series of papers that focus on parental and alloparental investment across five populations, this special issue of Human Nature uses evolutionary theory to examine how socioecological context influences modes of direct parental investment among the boat-dwelling Shodagor of Bangladesh (Starkweather), modes of indirect paternal investment in the modern United States (Anderson), and the biological outcome of paternal investment for men in Jamaica (Gray et al.), as well as direct alloparental investment among village Bangladeshis (Perry) and indirect alloparental investment in breastfeeding practices in the United States (Cisco). [ABSTRACT FROM AUTHOR]

Whereas many evolutionary models emphasize within-group cooperation or between-group competition in explaining human large-scale cooperation, recent work highlights a critical role for intergroup cooperation in human adaptation. Here we investigate intergroup cooperation in the domain of shotgun hunting in northern Republic of the Congo. In the Congo Basin broadly, forest foragers maintain relationships with neighboring farmers based on systems of exchange regulated by norms and institutions such as fictive kinship. In this study, we examine how relationships between Yambe farmers and BaYaka foragers support stable intergroup cooperation in the domain of shotgun hunting. In the study village, shotgun hunting is based on a specialization-based exchange wherein Yambe farmers contribute shotguns and access to markets to buy cartridges and sell meat while BaYaka foragers contribute their specialized forest knowledge and skill. To understand how costs and benefits are distributed, we conducted structured interviews with 77 BaYaka hunters and 15 Yambe gun owners and accompanied hunters on nine hunting trips. We found that hunts are organized in a conventional manner within a fictive kinship structure, consistent with the presence of intercultural mechanisms to stabilize cooperation. However, because bushmeat demand is high, gun owners can gain significant cash profit, while compensating hunters only with cigarettes, alcohol, and a traditional hunter's portion of meat. To level payoffs, hunters strategically hide kills or cartridges from gun owners to feed their own families. Our results illustrate how each group prioritizes different currencies (e.g., cash, meat, family, intergroup relations) and provide insights into how intergroup cooperation is stabilized in this setting. The example of this long-standing intergroup cooperative system is discussed in terms of its contemporary entwinement with logging, the bushmeat trade, and growing market intersection. [ABSTRACT FROM AUTHOR]

Factors such as subsistence turnover, warfare, or interaction between different groups can be major sources of cultural change in human populations. Global demographic shifts such as the transition to agriculture during the Neolithic and more recently the urbanization and globalization of the twentieth century have been major catalysts for cultural change. Here, we test whether cultural traits such as patri/matrilocality and postmarital migration persist in the face of social upheaval and gene flow during the past 150 years in postcolonial South Africa. The recent history of South Africa has seen major demographic shifts that resulted in the displacement and forced sedentism of indigenous Khoekhoe and San populations. During the expansion of the colonial frontier, the Khoe-San admixed with European colonists and enslaved individuals from West/Central Africa, Indonesia, and South Asia, introducing novel cultural norms. We conducted demographic interviews among Nama and Cederberg communities representing nearly 3,000 individuals across three generations. Despite the history of colonial expansion, and the subsequent incorporation of Khoe-San and Khoe-San-descendant communities into a colonial society with strong patrilocal norms, patrilocality is the least common postmarital residence pattern in our study populations today. Our results suggest that more recent forces of integration into the market economy are likely the primary drivers of change in the cultural traits examined in our study. Birthplace had a strong effect on an individual's odds of migration, distance moved, and postmarital residence form. These effects are at least partially explained by the population size of the birthplace. Our results suggest that market factors local to birthplaces are important drivers of residence decisions, although the frequency of matrilocal residence and a geographic and temporal cline in migration and residence patterns also indicate the persistence of some historic Khoe-San cultural traits in contemporary groups. [ABSTRACT FROM AUTHOR]

Humans are social animals that rely on different ways to interact with each other. The COVID-19 pandemic strongly changed our communication strategies. Because of the importance of direct contact for our species, we predict that immediately after the forced social isolation, people were more prone to engage in direct rather than in virtual interactions, thus showing a lower mimicry response in the use of smartphones. In a non-longitudinal study, we collected behavioral data under naturalistic contexts and directly compared the data of the mimicry response gathered immediately following the Italian lockdown (May–September 2020) with those gathered one year later (May–October 2021). Contrary to our expectations, the mimicry response in the use of smartphones was higher immediately after the lockdown than a year later. Probably the large use of these devices during the lockdown translated into a greater sensitivity to be affected by others' smartphone manipulation. Indeed, social isolation modified, at least in the short term, the ways we interact with others by making us more prone to engage in "virtual" social interactions. The bright side of the coin unveiled by our findings is that the effect seems to diminish over time. The large behavioral dataset analyzed here (1,608 events; 248 people) also revealed that the mimicry response in the use of smartphones was higher between familiar subjects than between strangers. In this view, mimicry in manipulating smartphones can be considered an example of joint action that fosters behavioral synchrony between individuals that, in the long-term, can translate into the formation of social bonding. [ABSTRACT FROM AUTHOR]

There is a popular idea that archaic humans commonly used wooden clubs as their weapons. This is not based on archaeological finds, which are minimal from the Pleistocene, but rather on a few ethnographic analogies and the association of these weapons with simple technology. This article presents the first quantitative cross-cultural analysis of the use of wooden clubs and throwing sticks for hunting and violence among foragers. Using a sample of 57 recent hunting-gathering societies from the Standard Cross-Cultural Sample, it is shown that the majority used clubs for violence (86%) and/or hunting (74%). Whereas in hunting and fishing the club usually served only as a secondary tool, 33% of societies used the club as one of their main fighting weapons. The use of throwing sticks was less frequent among the societies surveyed (12% for violence, 14% for hunting). Based on these results and other evidence, it is argued that the use of clubs by early humans was highly probable, at least in the simplest form of a crude stick. The great variation in the forms and use of clubs and throwing sticks among recent hunter-gatherers, however, indicates that they are not standardized weapons and that similar variation may have existed in the past. Many such prehistoric weapons may therefore have been quite sophisticated, multifunctional, and carried strong symbolic meaning. [ABSTRACT FROM AUTHOR]

Folk stories featuring prosocial content are ubiquitous across cultures. One explanation for the ubiquity of such stories is that stories teach people about the local socioecology, including norms of prosociality, and stories featuring prosocial content may increase generosity in listeners. We tested this hypothesis in a sample of 185 Hadza hunter-gatherers. We read participants a story in which the main character either swims with another person (control story) or rescues him from drowning (prosocial story). After hearing the story, participants played a dictator game with dried meat sticks and then were given a recall test of facts presented in the story. There was moderate evidence for a small effect of the prosocial story: participants who heard the prosocial story gave an estimated 0.22 [90% HDI: −0.12–0.57] more meat sticks than those who heard the control story. However, the association between generosity and sex, marital status, and region of residence was stronger; men gave more than women, unmarried participants gave more than married participants, and participants living in a region with more exposure to markets gave more than participants living further from markets. There was no evidence that the prosocial story was more easily recalled than the control story. These results provide some support for the hypothesis that prosocial stories can increase prosociality in listeners, though the effect of hearing a single story is small. [ABSTRACT FROM AUTHOR]

When people get ill, they naturally want to restore health through medical interventions. Here I model a situation in which individuals can psychologically entertain multiple potential treatments at once: when illness occurs, individuals would attempt one treatment first, and if it fails to produce an observable effect within a particular time period, a second treatment is attempted, and the eventual recovery is attributed to the treatment that is temporally closer. This creates population dynamics wherein the therapeutic power of the superior/effective medical treatments is misattributed to inferior/ineffective treatments. Through both analytic formulation and agent-based simulation, I show that the equilibrium frequencies of different treatment variants depend on their natural variability in the effect timing, the level of individual patience, and the number of cultural models sampled by the naive individual. Both ineffective and effective medical treatments may stably coexist in the population under a range of parameter settings. [ABSTRACT FROM AUTHOR]

I present a detailed ethnographic study of magic and divination of the Nuosu people in southwest China and offer a cognitive account of the surprising prevalence of these objectively ineffective practices in a society that has ample access to modern technology and mainstream Han culture. I argue that in the belief system of the Nuosu, ghosts, divination, and magical healing rituals form a closely interconnected web that gives sense and meaning to otherwise puzzling practices, and such a belief system is importantly supported and reinforced by individual's everyday experiences. Contemporary Nuosu people overwhelmingly treat these practices as instruments for achieving specific ends and often entertain considerable uncertainty regarding their efficacy, which may be overestimated for a number of reasons, including the following: (1) the intuitive plausibility of divination for ghost identification and exorcist rituals is enhanced by the belief in the existence of ghosts as a result of abductive reasoning, (2) negative instances (divinatory or healing ritual failures) are underreported, and (3) people's misperception of the probability of uncertain events' occurrence often prevents them from realizing that the efficacies of magical/divinatory practices do not outperform chance. I conclude with some comments on the generalizability of the psychological and social mechanisms discussed. [ABSTRACT FROM AUTHOR]

Figurative drawing is a skill that takes time to learn, and it evolves during different childhood phases that begin with scribbling and end with representational drawing. Between these phases, it is difficult to assess when and how children demonstrate intentions and representativeness in their drawings. The marks produced are increasingly goal-oriented and efficient as the child's skills progress from scribbles to figurative drawings. Pre-figurative activities provide an opportunity to focus on drawing processes. We applied fourteen metrics to two different datasets (N = 65 and N = 344) to better understand the intentional and representational processes behind drawing, and combined these metrics using principal component analysis (PCA) in different biologically significant dimensions. Three dimensions were identified: efficiency based on spatial metrics, diversity with color metrics, and temporal sequentiality. The metrics at play in each dimension are similar for both datasets, and PCA explains 77% of the variance in both datasets. Gender had no effect, but age influenced all three dimensions differently. These analyses for instance differentiate scribbles by children from those drawn by adults. The three dimensions highlighted by this study provide a better understanding of the emergence of intentions and representativeness in drawings. We discussed the perspectives of such findings in comparative psychology and evolutionary anthropology. [ABSTRACT FROM AUTHOR]

Many cognitive and evolutionary theories of religion argue that supernatural explanations are byproducts of our cognitive adaptations. An influential argument states that our supernatural explanations result from a tendency to generate anthropomorphic explanations, and that this tendency is a byproduct of an error management strategy because agents tend to be associated with especially high fitness costs. We propose instead that anthropomorphic and other supernatural explanations result as features of a broader toolkit of well-designed cognitive adaptations, which are designed for explaining the abstract and causal structure of complex, unobservable, and uncertain phenomena that have substantial impacts on fitness. Specifically, we argue that (1) mental representations about the abstract vs. the supernatural are largely overlapping, if not identical, and (2) when the data-generating processes for scarce and ambiguous observations are complex and opaque, a naive observer can improve a bias-variance trade-off by starting with a simple, underspecified explanation that Western observers readily interpret as "supernatural." We then argue that (3) in many cases, knowledge specialists across cultures offer pragmatic services that involve apparently supernatural explanations, and their clients are frequently willing to pay them in a market for useful and effective services. We propose that at least some ethnographic descriptions of religion might actually reflect ordinary and adaptive responses to novel problems such as illnesses and natural disasters, where knowledge specialists possess and apply the best available explanations about phenomena that would otherwise be completely mysterious and unpredictable. [ABSTRACT FROM AUTHOR]

Most research on transmission biases in cultural evolution has treated different biases as distinct strategies. Here I present a model that combines both frequency dependent bias (including conformist bias) and payoff bias in a single decision-making calculus and show that such an integrated learning strategy may be superior to relying on either bias alone. Natural selection may operate on humans' relative dependence on frequency and payoff information, but both are likely to contribute to the spread of variants with high payoffs. Importantly, the magnitude of conformist bias affects the evolutionary dynamics, and I show that an intermediate level of conformity may be most adaptive and may spontaneously evolve as it resists the invasion of low-payoff variants yet enables the fixation of high-payoff variants in the population. [ABSTRACT FROM AUTHOR]

Intergroup and long-distance relationships are both central features of human social life, but because intergroup relationships are emphasized in the literature, long-distance relationships are often overlooked. Here, we make the case that intergroup and long-distance relationships should be studied as distinct, albeit related, features of human sociality. First, we review the functions of both kinds of relationship: while both can be conduits for difficult-to-access resources, intergroup relationships can reduce intergroup conflict whereas long-distance relationships are especially effective at buffering widespread resource shortfalls. Second, to illustrate the importance of distinguishing the two relationship types, we present a case study from rural Bolivia. Combining ethnography and two different experimental techniques, we find that the importance of intergroup relationships—and the salience of group membership itself—varies across populations and across methods. Although ethnography revealed that participants often rely on long-distance relationships for resource access, we were unable to capture participant preferences for these relationships with a forced-choice technique. Taken together, our review and empirical data highlight that (1) intergroup and long-distance relationships can have different functions and can be more or less important in different contexts and (2) validating experimental field data with ethnography is crucial for work on human sociality. We close by outlining future directions for research on long-distance relationships in humans. [ABSTRACT FROM AUTHOR]

Weight- (WAZ), height- (HAZ), and BMI-for-age (BMIZ) are frequently used to assess malnutrition among children. These measures represent different categories of risk and are usually hypothesized to be affected by distinct factors, despite their inherent relatedness. Life history theory suggests weight should be sacrificed before height, indicating a demonstrable relationship among them. Here we evaluate impact of family composition and household economics on these measures of nutritional status and explore the role of WAZ as a factor in HAZ. Anthropometrics, family demographics, and measures of household economy were collected from Sidama agropastoralist children in a peri-urban village in southwestern Ethiopia (n = 157; 79 girls). Just over half of the sample (50.9%) had z-scores of − 2SD or below on at least one measure, indicating an elevated risk of morbidity/mortality; 30% were at or below − 2SD on two or more measures. We used hierarchical linear regression with random intercept analysis to model WAZ and HAZ. Siblings and crop sales significantly decrease WAZ while electricity, agriculture, and polygyny improve z-scores; however, an interaction between polygyny and siblings indicates negative effects of siblings in polygynous families and positive effects in nonpolygynous ones (adj. R2 = 66.5%). For HAZ, agriculture and electricity are positively associated with z-scores whereas siblings have a negative effect; the interaction term again indicates that effects of siblings vary in polygynous and nonpolygynous families (adj. R2 = 74.2%). A mediation model exploring the role of weight in height outcomes suggests not only that WAZ has direct effects on HAZ but also that effects of electricity and agriculture on HAZ are partially mediated by WAZ. Our findings indicate that WAZ and HAZ are primarily affected by shared variables, but effects of siblings vary by polygyny status. Long-term outcomes (HAZ) among Sidama children would likely benefit from interventions focused on stabilizing WAZ across family members. [ABSTRACT FROM AUTHOR]

After they diverged from panins, hominins evolved an increasingly committed terrestrial lifestyle in open habitats that exposed them to increased predation pressure from Africa's formidable predator guild. In the Pleistocene, Homo transitioned to a more carnivorous lifestyle that would have further increased predation pressure. An effective defense against predators would have required a high degree of cooperation by the smaller and slower hominins. It is in the interest of predator and potential prey to avoid encounters that will be costly for both. A wide variety of species, including carnivores and apes and other primates, have therefore evolved visual and auditory signals that deter predators by credibly signaling detection and/or the ability to effectively defend themselves. In some cooperative species, these predator deterrent signals involve highly synchronized visual and auditory displays among group members. Hagen and Bryant (Human Nature, 14(1), 21–51, 2003) proposed that synchronized visual and auditory displays credibly signal coalition quality. Here, this hypothesis is extended to include credible signals to predators that they have been detected and would be met with a highly coordinated defensive response, thereby deterring an attack. Within-group signaling functions are also proposed. The evolved cognitive abilities underlying these behaviors were foundations for the evolution of fully human music and dance. [ABSTRACT FROM AUTHOR]