Using homicide rates as an indicator, this article examines the ecological factors that might be functioning as stressors in the environment of thirty-four East African tribes. A series of hypotheses dealing with the relationships between these stressors and tribal levels of aggressiveness are tested.

This article examines the relationship between pathogen stress and polygyny. Results indicate that there is a positive association between the two that is not confounded by geographic region, latitude, population density, male-male competition, or presence of brideprice. In particular, pathogen stress precicts higher levels of non-sororal polygyny and capturing women for wives or concubines.

This paper "reduces Murdock's 210 categories to 30 variables, and intercorrelates and factor analyzes the variables for six world subdivisions as well as for the entire world." This article also discusses factor analysis as a method and examines the correlations more closely between the two regions that differed the most, North America and the Circum-Mediterranean.