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Human Nature

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ISSN (Print) 1936-4776 - ISSN (Online) 1045-6767
Published by Springer-Verlag

[2216 journals]

When Romance and Rivalry Awaken
- Abstract: Abstract Previous research indicates positive effects of a person’s attractiveness on evaluations of opposite-sex persons, but less positive or even negative effects of attractiveness on same-sex evaluations. These biases are consistent with social motives linked to mate search and intrasexual rivalry. In line with the hypothesis that such motives should not become operative until after puberty, 6- to 12-year-old participants (i.e., children) displayed no evidence for biased social evaluations based on other people’s attractiveness. In contrast, 13- to 19-year-old participants (i.e., adolescents) displayed positive and negative attractiveness biases toward opposite- and same-sex targets, respectively. Moreover, these biases increased with the age—and thus the reproductive relevance—of the targets being evaluated. Findings corroborate the relevance of mating-related motives for social judgment and illustrate how such biases can grow during human development. At a broader conceptual level, this research demonstrates the utility of investigating proximate social judgment processes through the lens of adaptationist thinking.
  PubDate: 2013-05-12
How Do Rituals Affect Cooperation?
- Abstract: Abstract Collective rituals have long puzzled anthropologists, yet little is known about how rituals affect participants. Our study investigated the effects of nine naturally occurring rituals on prosociality. We operationalized prosociality as (1) attitudes about fellow ritual participants and (2) decisions in a public goods game. The nine rituals varied in levels of synchrony and levels of sacred attribution. We found that rituals with synchronous body movements were more likely to enhance prosocial attitudes. We also found that rituals judged to be sacred were associated with the largest contributions in the public goods game. Path analysis favored a model in which sacred values mediate the effects of synchronous movements on prosocial behaviors. Our analysis offers the first quantitative evidence for the long-standing anthropological conjecture that rituals orchestrate body motions and sacred values to support prosociality. Our analysis, moreover, adds precision to this old conjecture with evidence of a specific mechanism: ritual synchrony increases perceptions of oneness with others, which increases sacred values to intensify prosocial behaviors.
  PubDate: 2013-05-11
Red, Yellow, and Super-White Sclera
- Abstract: Abstract The sclera, the eye’s tough outer layer, is, among primates, white only in humans, providing the ground necessary for the display of colors that vary in health and disease. The current study evaluates scleral color as a cue of socially significant information about health, attractiveness, and age by contrasting the perception of eyes with normal whites with copies of those eyes whose whites were reddened, yellowed, or further whitened by digital editing. Individuals with red and yellow sclera were rated to be less healthy, less attractive, and older than individuals with untinted control sclera. Individuals with whitened, “super-white” sclera were rated as younger, although not more healthy or attractive, than controls. In humans, clear, white sclera may join such traits as smooth skin and long, lustrous hair as signs of health, beauty, and reproductive fitness. The evolution of a white sclera may have contributed to the emergence of humans as a social species.
  PubDate: 2013-05-11
Individual Differences in Reproductive Strategy are Related to Views about Recreational Drug Use in Belgium, The Netherlands, and Japan
- Abstract: Abstract Individual differences in moral views are often explained as the downstream effect of ideological commitments, such as political orientation and religiosity. Recent studies in the U.S. suggest that moral views about recreational drug use are also influenced by attitudes toward sex and that this relationship cannot be explained by ideological commitments. In this study, we investigate student samples from Belgium, The Netherlands, and Japan. We find that, in all samples, sexual attitudes are strongly related to views about recreational drug use, even after controlling for various ideological variables. We discuss our results in light of reproductive strategies as determinants of moral views.
  PubDate: 2013-05-10
Violence, Teenage Pregnancy, and Life History
- Abstract: Abstract Guided by principles of life history strategy development, this study tested the hypothesis that sexual precocity and violence are influenced by sensitivities to local environmental conditions. Two models of strategy development were compared: The first is based on indirect perception of ecological cues through family disruption and the second is based on both direct and indirect perception of ecological stressors. Results showed a moderate correlation between rates of violence and sexual precocity (r = 0.59). Although a model incorporating direct and indirect effects provided a better fit than one based on family mediation alone, significant improvements were made by linking some ecological factors directly to behavior independently of strategy development. The models support the contention that violence and teenage pregnancy are part of an ecologically determined pattern of strategy development and suggest that while the family unit is critical in affecting behavior, individuals’ direct experiences of the environment are also important.
  PubDate: 2013-05-08
Witchcraft Beliefs and Witch Hunts
- Abstract: Abstract This paper proposes an interdisciplinary explanation of the cross-cultural similarities and evolutionary patterns of witchcraft beliefs. It argues that human social dilemmas have led to the evolution of a fear system that is sensitive to signs of deceit and envy. This was adapted in the evolutionary environment of small foraging bands but became overstimulated by the consequences of the Agricultural Revolution, leading to witch paranoia. State formation, civilization, and economic development abated the fear of witches and replaced it in part with more collectivist forms of social paranoia. However, demographic-economic crises could rekindle fear of witches—resulting, for example, in the witch craze of early modern Europe. The Industrial Revolution broke the Malthusian shackles, but modern economic growth requires agricultural development as a starting point. In sub-Saharan Africa, witch paranoia has resurged because the conditions for agricultural development are lacking, leading to fighting for opportunities and an erosion of intergenerational reciprocity.
  PubDate: 2013-05-07
Cross-Cultural and Site-Based Influences on Demographic, Well-being, and Social Network Predictors of Risk Perception in Hazard and Disaster Settings in Ecuador and Mexico
- Abstract: Abstract Although virtually all comparative research about risk perception focuses on which hazards are of concern to people in different culture groups, much can be gained by focusing on predictors of levels of risk perception in various countries and places. In this case, we examine standard and novel predictors of risk perception in seven sites among communities affected by a flood in Mexico (one site) and volcanic eruptions in Mexico (one site) and Ecuador (five sites). We conducted more than 450 interviews with questions about how people feel at the time (after the disaster) regarding what happened in the past, their current concerns, and their expectations for the future. We explore how aspects of the context in which people live have an effect on how strongly people perceive natural hazards in relationship with demographic, well-being, and social network factors. Generally, our research indicates that levels of risk perception for past, present, and future aspects of a specific hazard are similar across these two countries and seven sites. However, these contexts produced different predictors of risk perception—in other words, there was little overlap between sites in the variables that predicted the past, present, or future aspects of risk perception in each site. Generally, current stress was related to perception of past danger of an event in the Mexican sites, but not in Ecuador; network variables were mainly important for perception of past danger (rather than future or present danger), although specific network correlates varied from site to site across the countries.
  PubDate: 2013-04-06
Introduction to “Coping with Environmental Risk and Uncertainty: Individual and Cultural Responses”
- Abstract: Abstract The papers in this special issue of Human Nature collectively consider societal and individual responses to a wide variety of environmental and social risks. The first paper considers societal level effects of pathogen risk on collectivism and conformity, avoidance of outsiders, and in-group loyalty in a worldwide cross-cultural sample. The second deals with societal-level effects of resource unpredictability on the nature and conduct of warfare in eastern Africa. The third deals with effects of volcanic eruptions and earthquakes and mediating factors on individual perceptions of risk in Mexico and Ecuador. The final paper deals with effects of various types of father absence on women’s reproductive life histories in Bangladesh.
  PubDate: 2013-04-02
Pathogen Prevalence, Group Bias, and Collectivism in the Standard Cross-Cultural Sample
- Abstract: Abstract It has been argued that people in areas with high pathogen loads will be more likely to avoid outsiders, to be biased in favor of in-groups, and to hold collectivist and conformist values. Cross-national studies have supported these predictions. In this paper we provide new pathogen codes for the 186 cultures of the Standard Cross-Cultural Sample and use them, together with existing pathogen and ethnographic data, to try to replicate these cross-national findings. In support of the theory, we found that cultures in high pathogen areas were more likely to socialize children toward collectivist values (obedience rather than self-reliance). There was some evidence that pathogens were associated with reduced adult dispersal. However, we found no evidence of an association between pathogens and our measures of group bias (in-group loyalty and xenophobia) or intergroup contact.
  PubDate: 2013-02-01
Does Absence Matter?
- Abstract: Abstract This paper examines the effects of three different types of father absence on the timing of life history events among women in rural Bangladesh. Age at marriage and age at first birth are compared across women who experienced different father presence/absence conditions as children. Survival analyses show that daughters of fathers who divorced their mothers or deserted their families have consistently younger ages at marriage and first birth than other women. In contrast, daughters whose fathers were labor migrants have consistently older ages at marriage and first birth. Daughters whose fathers died when they were children show older ages at marriage and first birth than women with divorced/deserted fathers and women with fathers present. These effects may be mediated by high socioeconomic status and high levels of parental investment among the children of labor migrants, and a combination of low investment, high psychosocial stress, and low alloparental investment among women with divorced/deserted fathers. Our findings are most consistent with the Child Development Theory model of female life history strategies, though the Paternal Investment and Psychosocial Acceleration models also help explain differences between women in low paternal investment situations (e.g., father divorced/abandoned vs. father dead). Father absence in and of itself seems to have little effect on the life history strategies of Bangladeshi women once key reasons for or correlates of absence are controlled, and none of the models is a good predictor of why women with deceased fathers have delayed life histories compared with women whose fathers are present.
  PubDate: 2013-01-01
Risk, Uncertainty, and Violence in Eastern Africa
- Abstract: Abstract Previous research on warfare in a worldwide sample of societies by Ember and Ember (Journal of Conflict Resolution, 36, 242–262, 1992a) found a strong relationship between resource unpredictability (particularly food scarcity caused by natural disasters) in nonstate, nonpacified societies and overall warfare frequency. Focusing on eastern Africa, a region frequently plagued with subsistence uncertainty as well as violence, this paper explores the relationships between resource problems, including resource unpredictability, chronic scarcity, and warfare frequencies. It also examines whether resource scarcity predicts more resource-taking in land, movable property, and people, as well as the commission of atrocities. Results support previous worldwide results regarding the relationship between resource unpredictability and warfare frequency. Results regarding resource-taking and atrocities are more nuanced and complex. In almost all findings, relationships are generally in opposite directions in nonstate and state societies. In post-hoc analyses, atrocities are significantly more likely to be committed in states than in nonstates.
  PubDate: 2012-12-01
Adaptive Social Learning Strategies in Temporally and Spatially Varying Environments
- Abstract: Abstract Long before the origins of agriculture human ancestors had expanded across the globe into an immense variety of environments, from Australian deserts to Siberian tundra. Survival in these environments did not principally depend on genetic adaptations, but instead on evolved learning strategies that permitted the assembly of locally adaptive behavioral repertoires. To develop hypotheses about these learning strategies, we have modeled the evolution of learning strategies to assess what conditions and constraints favor which kinds of strategies. To build on prior work, we focus on clarifying how spatial variability, temporal variability, and the number of cultural traits influence the evolution of four types of strategies: (1) individual learning, (2) unbiased social learning, (3) payoff-biased social learning, and (4) conformist transmission. Using a combination of analytic and simulation methods, we show that spatial—but not temporal—variation strongly favors the emergence of conformist transmission. This effect intensifies when migration rates are relatively high and individual learning is costly. We also show that increasing the number of cultural traits above two favors the evolution of conformist transmission, which suggests that the assumption of only two traits in many models has been conservative. We close by discussing how (1) spatial variability represents only one way of introducing the low-level, nonadaptive phenotypic trait variation that so favors conformist transmission, the other obvious way being learning errors, and (2) our findings apply to the evolution of conformist transmission in social interactions. Throughout we emphasize how our models generate empirical predictions suitable for laboratory testing.
  PubDate: 2012-12-01
Managing the Urban Commons
- Abstract: Abstract All communities have common resources that are vulnerable to selfish motives. The current paper explores this challenge in the specific case of the urban commons, defined as the public spaces and scenery of city neighborhoods. A theoretical model differentiates between individual incentives and social incentives for caring for the commons. The quality of a commons is defined as the level of physical (e.g., loose garbage) and social (e.g., public disturbances) disorder. A first study compared levels of disorder across the census block groups of a single city; the second compared the disorder generated by individual addresses in two neighborhoods. Each study found that homeownership, an individual incentive, was the main predictor of disorder. Owner-occupied parcels generated less disorder than their renter-occupied neighbors, but both parcel types produced less disorder in a neighborhood with greater homeownership. The results emphasize the need for considering both individual and social incentives for group-beneficial behaviors.
  PubDate: 2012-12-01
Intensification, Tipping Points, and Social Change in a Coupled Forager-Resource System
- Abstract: Abstract This paper presents a stylized bioeconomic model of hunter-gatherer foraging effort designed to study the process of intensification on open-access resources. A critical insight derived from the model is that the very success of an adaptation at the level of an individual forager group can create system-level vulnerabilities that subsequently feed back to cause emergent social change. The model illustrates how the intensification of harvest time by individuals within a habitat creates a forager-resource system that becomes vulnerable to perturbations. When the system is vulnerable, it is characterized by two resource harvest equilibria: a sustainable, low-effort equilibrium and a degraded, high-effort equilibrium. In this situation, the forager-resource system can be shocked back and forth between these different equilibria by perturbations, generating considerable risk for foragers. We use the model to isolate the ecological conditions under which the instability of the system generates the risk that foragers will experience a shortfall of resources, and we suggest a mechanism that might lead foragers to adopt social institutions that regulate who can access a habitat as an adaptive response. As an illustration of the potential utility of the insights drawn from the model, comparisons are made with a substantial ethnographic data set.
  PubDate: 2012-12-01
Review of Todd K. Shackelford and Viviana A. Weekes-Shackelford (Editors), The Oxford Handbook of Evolutionary Perspectives on Violence, Homicide, and War (Oxford & New York: Oxford University Press, 2012)
- PubDate: 2012-12-01
No Country for Old Men
- Abstract: Abstract Within affluent societies, people who grow up in deprived areas begin reproduction much earlier than their affluent peers, and they display a number of other behaviors adapted to an environment in which life will be short. The psychological mechanisms regulating life-history strategies may be sensitive to the age profile of the people encountered during everyday activities. We hypothesized that this age profile might differ between environments of different socioeconomic composition. We tested this hypothesis with a simple observational study comparing the estimated age distribution of people using the streets in an affluent and a socioeconomically deprived neighborhood which were closely matched in other ways. We were also able to use the UK census to compare the age profile of observed street users with the actual age profile of the community. We found that people over 60 years of age were strikingly less often observed on the street in the deprived than in the affluent neighborhood, whereas young adults were observed more often. These differences were not reflections of the different age profiles of people who lived there, but rather of differences in which residents use the streets. The way people use the streets varies with age in different ways in the affluent and the deprived neighborhoods. We argue that chronic exposure to a world where there are many visible young adults and few visible old ones may activate psychological mechanisms that produce fast life-history strategies.
  PubDate: 2012-12-01
Review of Wenda Trevathan’s Ancient Bodies, Modern Lives: How Evolution Has Shaped Women’s Health (New York: Oxford University Press, 2010)
- PubDate: 2012-12-01
Sex and Age Differences in Mate-Selection Preferences
- Abstract: Abstract For nearly 70 years, studies have shown large sex differences in human mate selection preferences. However, most of the studies were restricted to a limited set of mate selection criteria and to college students, and neglecting relationship status. In this study, 21,245 heterosexual participants between 18 and 65 years of age (mean age 41) who at the time were not involved in a close relationship rated the importance of 82 mate selection criteria adapted from previous studies, reported age ranges for the oldest and youngest partner that they would find acceptable, and responded to 10 yes/no questions about a potential marriage partner. For nearly all mate selection criteria, women were found to be the more demanding sex, although men placed consistently more value on the physical attractiveness of a potential partner than women. Also, the effects of the participants’ age and level of education were nearly negligible. These results demonstrate the robustness of sex differences in mate selection criteria across a substantial age range.
  PubDate: 2012-12-01
Cultural Macroevolution on Neighbor Graphs
- Abstract: Abstract What are the driving forces of cultural macroevolution, the evolution of cultural traits that characterize societies or populations? This question has engaged anthropologists for more than a century, with little consensus regarding the answer. We develop and fit autologistic models, built upon both spatial and linguistic neighbor graphs, for 44 cultural traits of 172 societies in the Western North American Indian (WNAI) database. For each trait, we compare models including or excluding one or both neighbor graphs, and for the majority of traits we find strong evidence in favor of a model which uses both spatial and linguistic neighbors to predict a trait’s distribution. Our results run counter to the assertion that cultural trait distributions can be explained largely by the transmission of traits from parent to daughter populations and are thus best analyzed with phylogenies. In contrast, we show that vertical and horizontal transmission pathways can be incorporated in a single model, that both transmission modes may indeed operate on the same trait, and that for most traits in the WNAI database, accounting for only one mode of transmission would result in a loss of information.
  PubDate: 2012-09-01
Sex Differences in Hadza Dental Wear Patterns
- Abstract: Abstract Among hunter-gatherers, the sharing of male and female foods is often assumed to result in virtually the same diet for males and females. Although food sharing is widespread among the hunting and gathering Hadza of Tanzania, women were observed eating significantly more tubers than men. This study investigates the relationship between patterns of dental wear, diet, and extramasticatory use of teeth among the Hadza. Casts of the upper dentitions were made from molds taken from 126 adults and scored according to the Murphy dental attrition scoring system. Females had significantly greater anterior occlusal wear than males when we controlled for age. Males exhibited greater asymmetry in wear, with greater wear on the left side in canines, first premolars, and first molars. We suggest that these sex differences in wear patterns reflect the differences seen in the diet, as well as in the use of teeth as tools.
  PubDate: 2012-09-01