Dopamine receptor D4 (DRD4) exhibits the largest number of polymorphisms of any dopamine receptor yet identified, and variation in DRD4 has been linked to variation in traits such as novelty-seeking and attention deficit/hyperactivity disorder. DRD4 also exhibits large variation between populations. Here, the authors test the hypothesis that natural selection acting on DRD4 may account for variation in between-population migratory patterns, using genetic and historical data from 39 populations.

Genetic, linguistic, and geographic data can be used to explain the distribution of cultural units ("semes") and to understand the evolutionary mechanisms of culture. Three broad models of cultural transmission attempt to explain why cultures share semes: (1) Cultural diffusion, emphasizing horizontal transmission. (2) Local adaptation, where trail-and-error learning leads to the independent adoption of semes by different peoples living in similar environments. (3) Demic diffusion, which emphasizes vertical and frequency-dependent transmission. Authors test the explanatory power of each model using cultural, genetic, linguistic and geographic data from 36 African cultures.

The ability of adults to digest lactose is common only in populations of European and circum-Mediterranean origin, a distribution thought to be a result of genetic adaptation to drinking milk from domestic livestock. Two additional hypotheses have been proposed to explain the distribution of high lactose digestion capacity: (1) supplemental calcium in high-latitude populations prone to vitamin D deficiency and (2) maintenance of water and electrolytes in the body in highly arid environments. However, these hypotheses are confounded by the shared ancestry of populations whose lactose digestion capability has been tested. Therefore, the authors test all three hypotheses using a phylogenetic comparative method for 62 cultures.

This article focuses on ecological correlates of sexual division in the control of resources. The author tests several ecological theories put forth by others. Sex coalitions are examined in humans, and sexual dimorphism in resource acquisition and control is discussed.

This study seeks to examine the influence that UV radiation and climate might have on gender inequality, and tests two extant theories on why gender inequality exists -- the life-history theory (aligned with climate) and the cognitive performance theory (aligned with UV radiation). The model with UV radiation as the main predictor fits the data on gender inequality the best, and pathogen prevalence and the ACP1*B allele were also found to be associated with gender inequality. The model was found to be robust across continents and ancestry. The study also highlights the need for further research to better understand the complex interplay of these factors in different cultures.

This article investigates peer relations in infancy, both in primates and in preindustrial human societies. Data from these populations shows a strong tendency toward a multi-age composition of play groups rather than solely peer-aged play groups for infants. Patterns in child care across societies of different subsistence types are empirically examined.

By testing relationships between musical, geographic, genetic, and linguistic distance among nine indigenous groups in Taiwan, the researchers aim to quantitatively evaluate a developing theory of coevolution between these traits. An especially strong correlation between musical variability and genetic distance suggests that music may possess worldwide time depth, diversity, and universality equal to or greater than that of language, and could thus serve as a complementary marker for reconstruction of long-term population shifts.

In this article, the authors seek to understand dog-human coevolution by considering predictors of different aspects of dog-human relationships across cultures. In order to measure dog-human relationships, the researchers created three indexes: dogs' utility for humans (DUH), humans' utility for dogs (HUD), and the personhood of dogs (PD). Each of these indexes were tested against various pre-coded variables that were empirically and theoretically relevant to this subject.

Researchers examine marriage patterns of 186 societies from the Standard Cross-Cultural Sample (SCCS). The eleven predictor variables are pathogen stress, arranged female marriages, population density, father roles during infancy, temperature, social stratification, wealth inequality, internal warfare, assault frequency, female agricultural contribution, and sex ratio. The two outcome variables measuring polygyny are cultural rules constraining polygyny and the percentage of married men who are polygynous. Controlling on phylogeny using a global supertree of the languages, analysis of marriage patterns reveals that assault frequency and pathogen stress are the strongest predictors of polygyny. These findings offer additional support for the theories of harem-defense polygyny and male genetic quality.

This article focuses on the effect of environmental extremes and unpredictability on human behavior and reproductive strategies. Significant correlations were found between environmental extremes and unpredictability and several variables, including mobility, subsistence mode, and degree of polygyny.