In the target article, we presented the hypothesis that parasite-stress variation was a causal factor in the variation of in-group assortative sociality, cross-nationally and across the United States, which we indexed with variables that measured different aspects of the strength of family ties and religiosity. We presented evidence supportive of our hypothesis in the form of analyses that controlled for variation in freedom, wealth resources, and wealth inequality across nations and the states of the USA. Here, we respond to criticisms (...) from commentators and attempt to clarify and expand the parasite-stress theory of sociality used to fuel our research presented in the target article. (shrink)

Van de Vliert's findings fit nicely with our recent arguments implying that (1) differentiated selfhood is partly motivated by requirements of cultural groups, and (2) free will mainly exists within culture. Some cultural groups promote individual freedom, whereas others constrict it so as to maintain elites' power and privilege. Thus, freedom is, to a great extent, a creation of culture.

Van de Vliert proposes a comprehensive explanation for differences in in diverse human populations based on climate and monetary resources. This intriguing approach, though derived from an evolutionary view covering all species, is based exclusively on human populations. This anthropocentric lens is challenged by ways of testing Van de Vliert's thesis more generally using playfulness as a surrogate for freedom.

Worldwide there are substantial differences within and between countries in aggression and violence. Although there are various exceptions, a general rule is that aggression and violence increase as one moves closer to the equator, which suggests the important role of climate differences. While this pattern is robust, theoretical explanations for these large differences in aggression and violence within countries and around the world are lacking. Most extant explanations focus on the influence of average temperature as a factor that triggers aggression, (...) or the notion that warm temperature allows for more social interaction situations in which aggression is likely to unfold. We propose a new model, CLimate, Aggression, and Self-control in Humans, that helps us to understand differences within and between countries in aggression and violence in terms of differences in climate. Lower temperatures, and especially larger degrees of seasonal variation in climate, call for individuals and groups to adopt a slower life history strategy, a greater focus on the future, and a stronger focus on self-control. The CLASH model further outlines that slow life strategy, future orientation, and strong self-control are important determinants of inhibiting aggression and violence. We also discuss how CLASH differs from other recently developed models that emphasize climate differences for understanding conflict. We conclude by discussing the theoretical and societal importance of climate in shaping individual and societal differences in aggression and violence. (shrink)

The fundamental postulate of sociobiology is that individuals exploit favorable environments to increase their genetic representation in the next generation. The data on fertility differentials among contemporary humans are not cotvietent with this postulate. Given the importance ofHomo sapiensas an animal species in the natural world today, these data constitute particularly challenging and interesting problem for both human sociobiology and sociobiology as a whole.The first part of this paper reviews the evidence showing an inverse relationship between reproductive fitness and “endowment” (...) in contemporary, urbanized societies. It is shown that a positive relationship is observed only for those cohorts who bore their children during a unique period of rising fertility, 1935–1960, and that these cohorts are most often cited by sociobiologists as supporting the central postulate of sociobiology. Cohorts preceding and following these show the characteristic inverse relationship between endowment and fertility. The second section reviews the existing so-ciobiological models of this inverse relationship, namely, those of Barkow, Burley, and Irons, as well as more informal responses among sociobiologists to the persistent violation of sociobiology's central postulate, such as those of Alexander and Dawkins. The third section asks whether the goals of sociobiology, given the violation of its fundamental postulate by contemporary human societies, might not be better thought of as applied rather than descriptive, with respect to these societies. A proper answer to this question begins with the measurement of the pace and direction of natural selection within modern human populations, as compared to other sources of change. The vast preponderance of the shifts in human trait distributions, including the IQ distribution, appears to be due to environmental rather than genetic change. However, there remains the question of just how elastic these distributions are in the absence of reinforcing genetic change. (shrink)

Behavioral scientists routinely publish broad claims about human psychology and behavior in the world's top journals based on samples drawn entirely from Western, Educated, Industrialized, Rich, and Democratic (WEIRD) societies. Researchers – often implicitly – assume that either there is little variation across human populations, or that these “standard subjects” are as representative of the species as any other population. Are these assumptions justified? Here, our review of the comparative database from across the behavioral sciences suggests both that there is (...) substantial variability in experimental results across populations and that WEIRD subjects are particularly unusual compared with the rest of the species – frequent outliers. The domains reviewed include visual perception, fairness, cooperation, spatial reasoning, categorization and inferential induction, moral reasoning, reasoning styles, self-concepts and related motivations, and the heritability of IQ. The findings suggest that members of WEIRD societies, including young children, are among the least representative populations one could find for generalizing about humans. Many of these findings involve domains that are associated with fundamental aspects of psychology, motivation, and behavior – hence, there are no obviousa priorigrounds for claiming that a particular behavioral phenomenon is universal based on sampling from a single subpopulation. Overall, these empirical patterns suggests that we need to be less cavalier in addressing questions ofhumannature on the basis of data drawn from this particularly thin, and rather unusual, slice of humanity. We close by proposing ways to structurally re-organize the behavioral sciences to best tackle these challenges. (shrink)

The current paper synthesizes theory and data from the field of life history (LH) evolution to advance a new developmental theory of variation in human LH strategies. The theory posits that clusters of correlated LH traits (e.g., timing of puberty, age at sexual debut and first birth, parental investment strategies) lie on a slow-to-fast continuum; that harshness (externally caused levels of morbidity-mortality) and unpredictability (spatial-temporal variation in harshness) are the most fundamental environmental influences on the evolution and development of LH (...) strategies; and that these influences depend on population densities and related levels of intraspecific competition and resource scarcity, on age schedules of mortality, on the sensitivity of morbidity-mortality to the organism’s resource-allocation decisions, and on the extent to which environmental fluctuations affect individuals versus populations over short versus long timescales. These interrelated factors operate at evolutionary and developmental levels and should be distinguished because they exert distinctive effects on LH traits and are hierarchically operative in terms of primacy of influence. Although converging lines of evidence support core assumptions of the theory, many questions remain unanswered. This review demonstrates the value of applying a multilevel evolutionary-developmental approach to the analysis of a central feature of human phenotypic variation: LH strategy. (shrink)

This paper examines why fundamental freedoms are so unevenly distributed across the earth. Climato-economic theorizing proposes that humans adapt needs, stresses, and choices of goals, means, and outcomes to the livability of their habitat. The evolutionary process at work is one of collectively meeting climatic demands of cold winters or hot summers by using monetary resources. Freedom is expected to be lowest in poor populations threatened by demanding thermal climates, intermediate in populations comforted by undemanding temperate climates irrespective of income (...) per head, and highest in rich populations challenged by demanding thermal climates. This core hypothesis is supported with new survey data across 85 countries and 15 Chinese provinces and with a reinterpretative review of results of prior studies comprising 174 countries and the 50 states in the United States. Empirical support covers freedom from want, freedom from fear, freedom of expression and participation, freedom from discrimination, and freedom to develop and realize one's human potential. Applying the theory to projections of temperature and income for 104 countries by 2112 forecasts that (a) poor populations in Asia, perhaps except Afghans and Pakistanis, will move up the international ladder of freedom, (b) poor populations in Africa will lose, rather than gain, relative levels of freedom unless climate protection and poverty reduction prevent this from happening, and (c) several rich populations will be challenged to defend current levels of freedom against worsening climato-economic livability. (shrink)

This paper investigates hypotheses drawn from two sources: (1) Belsky, Steinberg, and Draper’s (1991) attachment theory model of the development of reproductive strategies, and (2) recent life history models and comparative data suggesting that environmental risk and uncertainty may be potent determinants of the optimal tradeoff between current and future reproduction. A retrospective, self-report study of 136 American university women aged 19–25 showed that current recollections of early stress (environmental risk and uncertainty) were related to individual differences in adult time (...) preference and adult sexual behavior, and that individual differences in time preference were related to adult attachment organization and sexual behavior. These results are consistent with the hypothesis that perceptions of early stress index environmental risk and uncertainty and mediate the attachment process and the development of reproductive strategies. On this view individual differences in time preference are considered to be part of the attachment theoretical construct of an internal working model, which itself is conceived as an evolved algorithm for the contingent development of alternative reproductive strategies. (shrink)

Hot and cold climates have posed differential threats to human survival throughout history. Cold temperatures can pose direct threats to survival in themselves, whereas hot temperatures may pose threats indirectly through higher prevalence of infectious disease. These differential threats yield convergent predictions for the relationship between more demanding climates and freedom of expression, but divergent predictions for freedom from discrimination.

A climate that is too cold to grow crops for part of the year demands foresight and self-control skills. To the extent that a culture has developed intertemporal bargaining, its members will have more autonomy, but pay the cost of being more compulsive, than members of societies that have not. Monetary resources will be a consequence but will also be fed back as a cause.