The second and third parts of this book classify the economic systems of foraging and agricultural societies in the SCCS based on correlations between their institutions of property an distribution. These economic types are then examined for relationships with other social, political, demographic, and environmental factors in order to draw tentative conclusions regarding the origins of the Agricultural and Industrial Revolutions. The fourth part of the book uses cross-national data to examine similar associations in industrial/service economies, and is not included here.

The article tests theories that may explain why warfare frequency varies from society to society. The focus is on ecological problems, particularly different kinds of resource scarcity, but social and psychological theories are also tested with both bivariate and multivariate analyses. Because unpredictable disasters are such a strong predictor in nonstate societies, the authors theorize that war may mostly be caused by a fear of nature.

This article tests a series of hypotheses differentiating internal warfare and external warfare. Results support the theory that internal warfare is a population control mechanism more common in patrilocal societies, whereas external warfare occurs between two societies, one of which recently migrated and adopted matrilocal residence. Based on these findings, the authors assert that internal warfare can be regulated while external warfare cannot.

Using a sample of 145 African societies, the authors seek to examine the relationship between segmentary lineage organization and conflict. Presented is evidence supporting the claim that segmentary lineage societies are more prone to conflict and to conflicts larger in scale and duration. The authors aim to contribute to a better understanding of the determinants of conflict, and additionally address the applicability of the present study beyond Africa.

This book investigates the evolution of military organizations and their activities. Hypotheses frequently relate military organizations to political variables. Data suggested that more politically centralized societies have more sophisticated military organizations which are more likely to be successful in conflict (though military sophistication does not appear to deter attack).

Authors investigate the cross-cultural correlates of games of chance. They advance a "conflict-enculturation" model to explain why individuals choose to engage in games of chance in particular (as opposed to games of strategy or physical skill). They suggest that games of chance are linked to cultures with antecedent conflict and/or feelings of powerlessness in the presence of uncertainty; both are psychological stressors whose effects may be assuaged by play with uncertainty models in the form of games of chance.

This chapter is concerned with correlates of warlikeness among non-industrial societies. Findings indicate that warlikeness is associated with climate, mobility, subsistence, political integration, division of labor, culture contact.

This study retests the data presented by Sillitoe (1977) in his study of the relationship between likelihood of warfare and population density in New Guinea. Contrary to Sillitoe, the author finds a strong and significant association between the two variables. The author also finds a significant relationship between the severity of food shortages and the frequency of warfare cross-culturally.

Inter-group variation is greater in humans than in any other animal, and scholars continue to debate the cause of this diversity. Two competing explanatory models of human variation emphasize either (1) ecological differences and "evoked" culture or (2) population-level effects of cultural transmission. The former emphasizes mechanisms that operate within a single generation, while the latter emphasizes cumulative cultural history operating over many generations. To test these competing models, the authors measured the relative power of ecological variables as compared to culture history to predict behavioral variation in 172 western North American tribes. Culture history is subdivided into culture phylogeny (based on language phylogeny) and spatial distance.

Using a cross-cultural sample of 91 societies, this paper draws on ecological theory to test if unpredictable environments will favor subsistence diversification. The general hypothesis is that societies with high climate unpredictability and resource stress would exhibit more subsistence diversity than societies in more stable climates. The authors examined four environmental and resource stress variables while controlling for temperature variance, subsistence activity, and phylogeny. Support was found for 2 of the 4 variables--chronic scarcity and environmental instability. In the discussion they suggest that more commonly observed events (e.g. annual hunger and climate unpredictability) may give people more motivation to change subsistence than rarer events (e.g. natural hazards and famine).