Identifying key socioecological factors influencing the expression of egalitarianism and inequality among foragers

Economic inequality is fueled by population scale, land-limited production, and settlement hierarchies across the archaeological record

Defining wealth broadly to include wealth in people, relational connections, and material possessions, we examine the prehistory of wealth inequality at the level of the residential units using the consistent proxy of Gini coefficients calculated across areas of contemporaneous residential units. In a sample of >1,100 sites and > 47,000 residential units spanning >10,000 y, persistent wealth inequality typically lags the onset of plant cultivation by more than a millennium. It accompanies landscape modifications and subsistence practices in which land (rather than labor) limits production, and growth of hierarchies of settlement size. Gini coefficients are markedly higher through time in settlements at or near the top of such hierarchies; settlements not enmeshed in these systems remain relatively egalitarian even long after plant and animal domestication. We infer that some households in top-ranked settlements were able to exploit the network effects, agglomeration opportunities, and (eventually) political leverage provided by these hierarchies more effectively than others, likely boosted by efficient intergenerational transmission of material resources after increased sedentism made that more common. Since population growth is associated with increased sedentism, more land-limited production, and the appearance and growth of settlement hierarchies, it is deeply implicated in the postdomestication rise of wealth inequality. Governance practices mediate the degree of wealth inequality, as do technical innovations such as the use of animals for portage, horseback riding, and the development of iron smelting.

Toward an evolutionary ecology of (in)equality

Inequality is increasingly recognized as a major problem in contemporary society. The causes and consequences of inequality in wealth and power have long been central concerns in the social sciences, whereas comparable research in biology has focused on dominance and reproductive skew. This theme issue builds on these existing research traditions, exploring ways they might enrich each other, with evolutionary ecology as a possibly unifying framework. Contributors investigate ways in which inequality is resisted or avoided and developed or imposed in societies of past and contemporary humans, as well as a variety of social mammals. Particular attention is paid to systematic, socially driven inequality in wealth (defined broadly) and the effects this has on differential power, health, survival and reproduction. Analyses include field studies, simulations, archaeological and ethnographic case studies, and analytical models. The results reveal similarities and divergences between human and non-human patterns in wealth, power and social dynamics. We draw on these insights to present a unifying conceptual framework for analysing the evolutionary ecology of (in)equality, with the hope of both understanding the past and improving our collective future. This article is part of the theme issue 'Evolutionary ecology of inequality'.