In this paper, the authors argue that polygyny creates social inequality in which economically advantaged men marry multiple women and economically disadvantaged men marry late in life or potentially never. The institution of polygyny results in a higher proportion of single men without families ("excess men"), who, the authors propose, may turn to violence to achieve higher wealth or prestige. Following this theory, the authors hypothesize that societies with more polygynous neighbors will be at higher risk for intergroup conflict, for which they find robust support. They also find that young men in polygynous societies, who are more likely to be economically disadvantaged and have less prestige, are also more likely to feel as though they are treated unequally and more ready to resort to violence, supporting the authors' theorized underlying mechanism.

Using a new measure called "territorial fractionalization" to indicate the extent to which traditional societies are split across current states, the authors of this study propose that fragmentation of ethnic groups and ethnonationalism is key to understanding civil conflict. They find that higher measures of territorial fractionalization significantly predict a higher risk of civil conflict, and that greater increases in territorial fractionalization also predict greater risk of civil conflict. These results hold for a global sample of data from 1945 to 2017, as well as in European and African subsamples dating back to 1886.

Using a new measure called "territorial fractionalization" to indicate the extent to which traditional societies are split across current states, the authors of this study propose that fragmentation of ethnic groups and ethnonationalism is key to understanding civil conflict. They find that higher measures of territorial fractionalization significantly predict a higher risk of civil conflict, and that greater increases in territorial fractionalization also predict greater risk of civil conflict. These results hold for a global sample of data from 1945 to 2017, as well as in European and African subsamples dating back to 1886.

This article examines the relationship between sexual dimorphism of stature and latitude; data support the association. The authors also find support for an association between latitude and human marriage systems, a variable proposed by Alexander (1979) to explain variation in sexual dimorphism of stature. When societies are categorized by latitude, the relationships between marriage systems and sexual dimorphism do not reach significance. Overall the authors emphasize the influence of environmental adaptation on sexual dimorphism rather than an explanation solely focused on male-male competition.

In this article Hames addresses the long-standing disagreements between evolutionary theories regarding human warfare (more specifically between Rousseauian and Hobbesian frameworks). This study posits that while most current and previous research focuses on the discrepancies between the frequency and intensity with which warfare takes place between hunter-gatherer and large-scale societies, the ability for societies to live in peace with their neighbors despite the possibility for warfare, is the most important evolutionary trait. Coexisting peacefully is what distinguishes human socially and politically from chimpanzees whereas warfare itself is a more primitive trait humans share with previous ancestors. Hames concludes that going forward, use of phylogenetic methods to control for common ancestry, and use of archaeological data would lead to new and more comprehensive findings. Although largely a review of principal warfare literature, Hames does present an original statistical finding on adult violence mortality which is reported below.

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 examines the origin of money. Anthropologists’ and economists’ theories are discussed and data supports a broad hypothesis that the existence of money is associated with level of economic development. The author further examines the emergence of internal, external, commercial and noncommercial moneys at high and low levels of economic development.

This article examines the origin of money. Anthropologists’ and economists’ theories are discussed and data supports a broad hypothesis that the existence of money is associated with level of economic development. The author further examines the emergence of internal, external, commercial and noncommercial moneys at high and low levels of economic development.

This article examines the relationship between sexual dimorphism of stature and latitude; data support the association. The authors also find support for an association between latitude and human marriage systems, a variable proposed by Alexander (1979) to explain variation in sexual dimorphism of stature. When societies are categorized by latitude, the relationships between marriage systems and sexual dimorphism do not reach significance. Overall the authors emphasize the influence of environmental adaptation on sexual dimorphism rather than an explanation solely focused on male-male competition.

This paper examines the relationship of productive variation in land between ethnic groups to determine if an increased range of producible goods will increase trade, thus decreasing language diversity between neighboring groups. The author initially found that high-variation in land production lessened the diversity of language between ethnic groups in that area. To further test this correlation, the author found that high-productive variation increased trade and exogamous marriage and decreased inter-ethnic conflict. Based on these findings, the author suggests that neighboring ethnic languages co-evolved through the economic benefit of inter-ethnic trade and social interaction.