This article reviews aspects of cooperative breeding in humans and nonhumans. Life history characteristics, childcare helpers, and demographic implications of cooperative breeding are examined. Cross-cultural data is presented, though no empirical hypotheses are tested.

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 article examines marital residence and sibling coresidence among horticulturalists in the South American lowlands. The authors reject a hypothesis that patrilocality is the defining trait of Amazonian tropical forest culture. Results on horticulturalists are compared with findings on hunter-gatherers: horticulturalists tend to be more uxorilocal. Empirical analysis also suggests that women tend to live with more kin later in life, and in large villages headmen live with more kin than nonheadmen.

This paper seeks to understand the roles played by children and adolescents in hunter-gatherer societies in relation to their social and ecological context. The authors set out to investigate how environmental factors, ecological risk, and the energetic contributions of adult men and women to food production may have influenced children/adolescent allocation of time to child care, domestic work, food production, and play. In order to carry out this study, the authors logged the behaviors of 690 children and adolescents from twelve hunter-gatherer and mixed-subsistence societies (Agta, Aka, Baka, BaYaka, Dukha, Hadza, Matsi-genka, Maya, Mayangna, Mikea, Pume, and Tsimane), totaling 85,597 unique observations. The study found that harsh environmental factors were not associated with child/adolescent time allocation, but that local ecological risk such as dangerous animals and lack of water availability predicted decreased time allocation to child care and domestic work, and that increased adult female participation in food production was associated with less time invested in child care among boys. It also found that all gendered differences in time allocation among children were stronger when men made greater contributions to food production than women. The authors interpret these results to signify that parents may play a role in preparing their children for environmental and ecological difficulty in order to help them develop skills that will help them become useful community members as adults.

In this article, the authors reconsider the polygyny threshold model in order to account for the "polygyny paradox." This paradox, as the authors define it, is the trend away from polygyny as societies adopt stratified agricultural economies. This is despite an increase in both the importance of material wealth and greater leaves of wealth inequality both of which would otherwise suggest increased polygyny. The authors develop a new model that does account for this paradox.

In this article researchers created a model to answer the question "What is a typical human life history of foraging skill?" While the immediate goal of this study was to create a model focused on age and relative skill, the larger purpose was to draw more clarity around the trajectory of human foraging skill over time. Researchers used data on hunting returns from 40 different study sites from around the world (Table 1) in order to assess the success of an expedition. While the model created here does not draw conclusions as to the absolute levels of production within or between societies, it can inform cross-cultural comparisons of relative skill at different stages of life. In conclusion, researchers found that the average hunter peaks at 33 years old, and by age 18, has 89% maximum skill (with the range of maximum skill being from ages 24-25). This skill was also found to decline slowly, such that it falls below 89% maximum after age 56. In terms of cross-cultural findings, the model found that cross-cultural variation is evident in the rate at which hunters develop peak skill, (meaning that within sites, the rate at which hunters develop skill is relatively homogeneous compared to the variation that distinguishes young hunters in different study sites), and individual hunters develop physical and cognitive abilities in concert, resulting in high hunting success by their late 20s and early 30s. In order to run the model, this study used the Hamiltonian Monte Carlo algorithm (in the Rstan package) for the sampling, and a Cobb-Douglas production function to express the observable foraging returns.