The authors examine multiple ecological variables as possible predictors of language diversity in North America using path analysis, mechanistic simulation modelling, and geographically weighted regression. They conclude that many of the variables do not predict language diversity, but rather are mediated by population density. The authors also find that the variables' ability to predict is not universal across the continent, but rather more regional.

Researchers examined both why so many language are spoken today, and why they are so unevenly distributed geographically. Instead of looking at correlative tests, this study uses a process-based simulation model that attempted to predict both the number or precolonial languages in Australia as well as the number of languages per unit of land. The model was based upon three basic assumptions: 1) humans fill unoccupied spaces; 2) rainfall limits population density; 3) groups divide after reaching a maximum population. While researchers used the model strictly on the Australia continent, it was able to correctly explain 56% of spatial variation in language richness, and predict the total number of languages across the continent. The accuracy of this model concludes that climatic conditions and changes in group size are important factors in shaping language diversity patterns and therefore global human cultural diversity.

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.

The authors investigate the relationship between linguistic diversity and various environmental and spatial variables associated with biodiversity. Most of these variables predict linguistic diversity variably across different continents, and more so within Africa and extended Asia (Asia, the Pacific, and Australia) than within Europe and the Americas. This divide is theorized to be a result of differences in demography and impact of colonialism between the two global regions. However, two environmental factors, landscape roughness and density of river systems, are found to be significant predictors across all global regions. The authors suggest that, as in processes of speciation, rough terrain and watercourses both create physical barriers between which languages can develop in isolation while, in the case of river junctions, also providing transportation routes whereby hybrid languages can occasionally manifest.

This paper builds off previous research into the effect of population size and resource risk on complexity of subsistence technology by investigating the relationship between these independent variables and total number of material items and techniques used by various western North American hunter-gatherer groups. This tally of total technological complexity is found to be insignificantly related to population size or residential mobility; however, there is a significant correlation in the expected direction between technological complexity and one measure of resource risk (mean annual temperature during driest month). Tying this finding to previous analyses of subsistence technologies, the authors theorize that environmental risk is a pervasive driver of technological ingenuity and cultural evolution.

This article explores the relationships between habitat and social organization among humans and other species. Diet, technology, group size, home range, mobility, kinship, marital residence, sexual division of labor, mating system, central places, food sharing, and egalitarianism are all considered.

Researchers investigated the variation of land tenure systems across forager societies using the economic defensibility model. The study attempted to explain the variation in tenure systems across 30 hunter-gatherer societies. Using data on defense and sharing of resources among groups, and indicators of resource density, resource predictability, and competition for resources, the researchers were unable to explain the variation. This study highlights the vast range of diversity and complexity of foragers subsistence strategies, and proposes that it may be more telling to conceptualize tenure systems among hunter-gatherer societies as assemblages of multiple property regimes. While there was no overall evidence that environmental variables of resource density and predictability explain variation in tenure systems, researchers did find that increasing population density, and greater competition for resources leads to greater territoriality.

This article investigates the adoption of agriculture. The author tests three possible predictors: environmental richness, population density, and division of labor by gender. Minimal support is found for these variables, and the author proposes two alternative explanations, based on diminishing returns in food production and balancing the food portfolio.

This study asks the following research questions: What are the dynamics of land ownership norms over time? Do these changes follow predetermined trajectories? The authors utilize biogeographical and evolutionary analyses to explore temporal and spatial patterns in land ownership norms within a sample of 73 Bantu societies. For the first component of the research, they test three prominent hypotheses regarding evolutionary trajectories: rectilinear, unilinear, and shift without restriction. For the second component, they use a multi-model inference approach to evaluate three hypotheses regarding the possible spatial patterns of land ownership. The results show evidence for the unilinear trajectory in type, but not with a consistent decrease in group ownership in size. Land ownership is more likely in areas with neighboring landowners and predictable resource productivity, while subsistence type is not significantly correlated with type of land ownership.

This article presents a representative theoretical model of the transition to agriculture. Empirical results from a cross-cultural sample provide support for the model. Results suggest that agriculture is associated with population density, technological sophistication, environment, and proximity to agricultural hearths, such as the Fertile Crescent.