Using t-test, generalized linear models (GLMs) and Bayesian regression models in a sample of 1188 pre-industrial societies, this study explores the research question: Why have foraging, horticulture, and pastoralism persisted into the 20th and 21st century? The authors test the marginal hypothesis and the oasis hypothesis of agricultural intensification. The first hypothesis suggests that foragers persisted because foragers predominantly inhabited marginal habitats that were typically unsuitable for agricultural purposes. The second hypothesis suggests that intensive agriculture emerged in regions characterized by limited biodiversity and a dependable water supply not reliant on local rainfall. In addition, the authors test whether specific kinds of biodiversity (elephants, malaria, and tsetse flies) correlate with agricultural intensification in African societies. The results support the marginal and oasis hypotheses, but only marginally support the African hypothesis, since only tsetse fly has a significant negative correlation to agricultural intensification.

This study uses Bayesian phylogenetic regression modelling across 131 largely non-industrial societies to test how variation of punishment is impacted by social, economic, and political organization. The authors focus on the presence of norm violations and types of punishments, and explores their relationships. The norm violations include adultery, rape, religious violations, food violations, and war cowardice. While the types of punishment are reputational, material, physical, or education. This study suggests a hypothesis for each type of punishment in relation to socioecological variables.