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.

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.

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.

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.

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.

This article explores the sexual division of labor among foragers, focusing on resource availability and constraints on women’s foraging activities. The authors conclude that “there is a greater division of foraging labor in more seasonal habitats where less gathering is possible and more extractive, tool-based foraging is required” (191).

The capacity for cumulative cultural evolution has often been invoked to explain the great diversity of habitats occupied by humans. This theory of cultural evolution emphasizes the gradual accumulation of technologies and cultural practices over many generations, and predicts that larger populations will generate more complex cultural adaptations than smaller, isolated ones. Here, the authors investigate the marine foraging tool repertoires of 10 Oceanic societies to determine whether population size and intergroup contact affect the cultural processes by which tool kits evolve.

In this study, the authors examine pathways to social inequality, specifically social class hierarchy, in 408 non-industrial societies. In a path model, they find social class hierarchy to be directly associated with increased population size, intensive agriculture and large animal husbandry, real property inheritance (unigeniture) and hereditary political succession, with an overall R-squared of 0.45. They conclude that a complex web of effects consisting of environmental variables, mediated by resource intensification, wealth transmission variables, and population size all shape social inequality.

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.