Grooming of conspecifics is thought to play an important social role among nonhuman primates, but the function and relative importance of such grooming among humans is unknown. Here the authors compare time spent grooming and conversing among six small-scale societies with grooming data from 69 nonhuman primate species. They test the hypothesis that conversation evolved among humans as an alternative way to obtain the social benefits (such as building and maintaining social alliances) of grooming in large groups.

This study utilizes Bayesian statistics to test the associations between harsh environments (specifically those with higher degrees of climate variability and relatively lower average temperature and precipitation) and alloparental care in societies throughout the world. Results support the hypothesis that societies in harsher environments show higher rates of alloparental care and that societies with higher rates of starvation and resource stress exhibit lower rates of alloparental care. The authors explain this theorizing that in the former relative costs are sufficiently outweighed by the benefits of this type of cooperation and in the latter they are not. They conclude that their results support the plasticity of human alloparenting as a response to varying ecology.

The researchers examine associations between male status and various measures of reproductive success among foraging/non-foraging, and monogamous/polygynous societies in order to test the "egalitarian hypothesis" which predicts lower status effects in hunter-gatherer groups. Contrary to this hypothesis, they find that male social status is equally significantly associated with reproductive success in foraging and nonforaging societies. Additional support is found for the "mating effort" hypothesis, which predicts that male reproductive success will be more associated with fertility than offspring mortality in polygynous societies, leading the authors to make various suggestions regarding the evolutionary mechanisms at play.

The research examines daily food sharing norms of 73 preindustrial societies from the Standard Cross-Cultural Sample. Multilevel regression models reveal that hunting and less predictable environments are not indicative of everyday food sharing, but offer support for many other predictions. Animal husbandry, external trade, daily labor sharing, and the presence of food storage are all predictive of daily food sharing practices whereas sharing is less common amongst large and stratified societies. These results align with evolutionary theories for food sharing practices.

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 is mainly concerned with understanding the motivators toward egalitarianism through modeling via a game that combined elements from both hawk-dove and prisoners dilemma. While most of the article is focused on this model, the researchers also tested their hypotheses cross-culturally on a sample of forager societies. In both cases, they found evidence that the benefits of cooperation drove egalitarianism.

This study explores predictors of variation in two dimensions of marital residence patterns among hunter-gatherers: 1) the tendency toward patrilocality versus matrilocality and 2) the tendency toward unilocality versus bilocality.

The present research investigates food sharing and labor sharing practices of 98 nonindustrial societies. The aims are to: 1) document the frequency and scope of sharing, and 2) test the theory that greater sharing is adaptive in societies subject to more resource stress (including natural hazards).

This article uses the Standard Cross-Cultural Samples to test the relationship between disease and economic growth among sub-Saharan African societies. The authors suggest that a higher disease prevalence limits social integration and economic development since pre-colonial times. The variable measuring economic growth is the complexity of large or impressive structures. The hypotheses are that 1) pathogen stress is negatively correlated to the presence of complex buildings, and 2) pathogen stress is positively correlated to increased ethnic diversity. The results support both hypotheses, and there are additional results, like 1) the negative correlation between pathogen stress and current income per capita and 2) the negative correlation between the increased ethnic diversity and current income per capita. Overall, this article shows the robust relationship between disease and economic development.

This study relates the type of games present in a society to the level of cultural complexity. Authors use a "game-type combination scale" that categorizes societies as having: 1) games of physical skill only; 2) games of physical skill and games of chance; and 3) games of physical skill, games of chance, and games of strategy. Results show a relationship between the game-type combination scale and indicators of cultural complexity.