New study reveals wealth inequality’s deep roots in human prehistory

PULLMAN, Wash. — Wealth inequality began shaping human societies more than 10,000 years ago, long before the rise of ancient empires or the invention of writing.

That’s according to a new study led by Washington State University archaeologist Tim Kohler that challenges traditional views that disparities in wealth emerged suddenly with large civilizations like Egypt or Mesopotamia. The research is part of a special issue of the Proceedings of the National Academy of Sciences, co-edited by Kohler and Amy Bogaard, an archaeologist at Oxford University in England.

Drawing on data from over 47,000 residential structures across 1,100 archaeological sites worldwide, the researchers used house sizes as a measure of wealth. Their analysis shows that wealth inequality started to increase roughly 1,500 years after the advent of agriculture in different civilizations across the world. This effect was driven by population growth, competition for land and the development of hierarchical settlements.

“Many people imagine early societies as egalitarian, but our research shows wealth inequality took root surprisingly early,” said Kohler. “The shift wasn’t instantaneous. It grew gradually as societies expanded, populations increased and resources became more constrained.”

The study highlights several key factors contributing to inequality. As farming communities grew, land became a finite resource, leading to competition and innovations like terracing and irrigation to boost productivity. Over time, larger settlements emerged as hubs of economic and political activity, where wealth began to concentrate in the hands of a few households. These wealth disparities were particularly evident in high population settlements, which exhibited greater inequality than smaller communities.

Tim Kohler

One of the study’s significant revelations is that wealth inequality predates written records, with evidence showing disparities existed even in the earliest agricultural societies. By applying the Gini coefficient—a standard measure of inequality—to ancient house sizes, researchers discovered that early farming villages were relatively egalitarian. However, as settlements became larger and more complex, economic disparities grew.

The study also challenges the idea that preindustrial societies lived in a “Malthusian world” of subsistence-level existence. Instead, Kohler and his team found evidence of steady wealth accumulation and technological advancements over millennia. The researchers point out that early agricultural societies often modified their landscapes—building terraces, draining wetlands, or creating irrigation systems—to intensify production. These innovations increased productivity but also widened the gap between those who controlled resources and those who did not.

Interestingly, the research revealed that some innovations, like iron smelting, often reduced inequality by increasing access to tools and resources for lower social strata. This finding challenges the assumption that technological advances always benefit elites. Kohler also noted that other factors, like the presence of large governing systems or collaborative social networks, played a role in mitigating or amplifying inequality over time.

“This isn’t just a modern problem,” Kohler said. “Understanding the origins of wealth inequality helps us see it as a persistent challenge that societies have been grappling with for thousands of years. The past has much to teach us about navigating these issues today.”

The study was a collaborative effort involving 27 researchers from institutions worldwide and was coordinated by the Coalition for Archaeological Synthesis, a not-for-profit organization dedicated to synthesizing the archaeological record to advance science and benefit society. By focusing on the period before written records, the researchers hope to fill a critical gap in understanding how human societies evolved, from egalitarian hunter-gatherer groups to complex, hierarchical communities.

“These patterns are deeply embedded in our history,” Kohler said. “But by studying them, we can better address their implications for the future. If we can understand how inequality emerged and evolved, perhaps we can learn how to mitigate its impact today.”