The Sources of Inequality

Abstract

This study investigates the long-term impact of shifting agricultural production technologies—or "land use systems"—and the concurrent rise of hierarchical institutions on socioeconomic inequality in ancient Western Asia. By blending recent insights from evolutionary biology regarding the environmental drivers of stratification with highly granular archaeological data, we develop an inferential framework to isolate the causal link between geography, agriculture, and the mediating role of political power. Our narrative follows a specific historical chain: environmental shifts in resource productivity triggered a fundamental transition from labor-limited subsistence to land-limited systems. This shift towards land-extensive cultivation generated unprecedented surpluses, incentivizing heavy investment in capital structures and specialized tools. These fixed investments created a "lock-in" effect, necessitating the emergence of formal political institutions to solve collective action problems, protect the property rights of investors, and defend accumulated wealth against external threats. To analyze this process, we exploit spatial and temporal climatic fluctuations as drivers behind the changes in land tenure and subsistence strategies. A central contribution of this research is the development of a new aggregated index for political institutions, which allows us to measure the evolution of governance alongside archaeological markers of wealth. By testing the effect of exogenous land-use changes on institutional complexity, and the subsequent conjoint effect of both on wealth distribution, this study reveals how the environment and human organization interacted to shape the evolution of the hierarchies of the ancient world. Our findings provide a robust empirical bridge between the biogeographic history of the Holocene and the institutional foundations of modern inequality.