This study tests four hypotheses that propose potential environmental and social predictors of toolkit size and complexity among hunter-gatherers. Hypotheses predicting relationships between population size, residential mobility, type of food resources and toolkit structure are not supported. Risk of resource failure is the only variable that is significantly associated with toolkit structure.

Prior research by Oswalt (1973, 1976) and Torrence (1983, 2001) has suggested that risk of resource failure is a significant predictor of toolkit complexity and diversity among hunter-gatherers. In this paper, the same relationship is tested among small-scale herding and farming groups. However, no significant correlation is discovered between any measure of resource risk and any measure of toolkit complexity. The researchers suggest that this absence may be the result of greater reliance on non-technological diversification methods among farmers (i.e. spatial diversification, mixed farming, intercropping), or of other unaccounted-for sources of risk (i.e. intergroup raiding and warfare).

Seeking to resolve contradictions between previous studies, these authors conduct empirical analysis on the relationship between population size and cultural evolution. Results indicate that population size influences toolkit richness and complexity, even when proxies for risk of resource failure are introduced in the regression model. Authors speculate that the association is weaker for hunter-gatherers because those societies are more affected by risk of resource failure and have institutions that facilitate cultural evolution despite smaller population size. There also may be a threshold effect in the influence of population size on toolkit structure.

The researchers test the relationship between toolkit complexity and diversity as defined by Oswalt (1973) and environmental and demographic variables. Neither population size nor risk of resource failure predict toolkit characteristics among all groups in the sample. However, population size is significantly positively correlated with toolkit diversity and complexity among food-producers, whereas environmental factors indicating risk of resource failure are significantly positively correlated among hunter-gatherers. This leads the researchers to suggest that food-producers' effectiveness at niche construction is a result of their large population size, which thus has a larger effect on toolkit composition than does environmental risk relative to hunter-gatherers.

Researchers investigated further into why and how humans speak so many languages across the globe, and why they are spread out unevenly. Using two different path analyses, a Stationary Path analysis and a GWPath, researchers tested the effect of eight different factors on language diversity. Out of the eight variables (river density, topographic complexity, ecoregion richness, temperature and precipitation constancy, climate change velocity, population density, and carrying capacity with group size limits), population density, carrying capacity with group size limit, and ecoregion richness had the strongest direct effects. Overall, the study revealed the role of multiple different mechanisms in shaping language richness patterns. The GWPath showed that not only does the most important predictor of language diversity vary over space, but predictors can also vary in the direction of their effects in different regions. They conclude that there is no universal predictor of language richness.

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.

Previous studies have yielded contradictory results on the relationship between population size and cultural evolution. Focusing on tool complexity these authors introduce the risk of resource failure as a possible confounding variable. They conclude that population does not predict tool kit complexity when controlling on other factors. There were significant correlations between tool kit complexity and some of the resource measures.

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.

In this paper, the authors analyzed data on 20 hunter-gatherer groups in order to understand the factors that influence the diversity and elaborateness of their tool assemblages. They used data collected by a variety of ethnographers to draw inferences about the complexity of implement assemblages and how it is affected by ecological constraints, modes of resource procurement, group movement, and population size. Regression analysis showed that the two strongest predictors of implement complexity were growth season (GS) (as a proxy for risk) and the number of annual residential moves (NMV). With the understanding that NMV and GS are likely not independent, the authors created addition and interaction models to understand how these variables may work in tandem to influence implement diversity and elaborateness. The results show that a shorter growing season (higher risk) and a lower number of moves are correlated with greater implement complexity. This analysis also divided the hunter-gatherers into two subgroups: a subgroup characterized by higher diversity of complex implements and more elaborate individual implements than predicted by the model, and a subgroup characterized by lower diversity and less elaborateness than predicted. These subgroups were found to correspond with the distinction between foragers (groups that move more-or-less as a unit while gathering) and collectors (groups that gather (logistically from a more-or-less fixed settlement), with the higher diversity subgroup being made up mostly of collectors and the lower diversity subgroup being made up mostly of foragers. Finally, the authors suggest that under conditions where population growth leads to increased density, foraging strategies will tend to shift to collector strategies in conjunction with increased elaborateness of implements to exploit resources with greater intensity.