Christian Peterson

In the largest study of its kind, researchers from 14 institutions, including the University of Hawaiʻi at Mānoa, saw disparities in wealth mount with the rise of agriculture, specifically the domestication of plants and large animals, and increased social organization.

The findings by the international team are published in Nature. The United States, researchers noted, currently has one of the highest levels of inequality in the history of the world.

The study gathered data from 63 archaeological sites or groups of sites. Comparing house sizes within each site, researchers assigned Gini coefficients, a common measure of inequality ranging from zero (perfect wealth equality) to one (wealth concentrated in one household).

The researchers’ models put the highest Ginis in the ancient Old World at .59, close to that of contemporary Greece’s .56 and Spain’s .58. It is well short of China’s .73 and the U.S.’s .80, a 2000 figure cited in the Nature paper. The 2016 Allianz Global Wealth Report puts the U.S. Gini at .81 and Tim Kohler, the lead author from Washington State University, has seen the U.S. Gini pegged at .85, “which is probably the highest wealth inequality for any developed country right now.”

The researchers found that hunter-gatherer societies typically had low wealth disparities, with a median Gini of .17. Their mobility would make it hard to accumulate wealth, let alone pass it on to subsequent generations. Horticulturalists—small-scale, low-intensity farmers—had a median Gini of .27. Larger scale agricultural societies had a median Gini of .35.

To the researchers’ surprise, inequality kept rising in the Old World while hitting a plateau in the New World. Researchers attribute this to the ability of Old World societies to harness big domesticated mammals like cattle and eventually horse and water buffalo. Draft animals, which were not available in the New World, let richer farmers till more land and expand into new areas. This increased their wealth while ultimately creating a class of landless peasants, researchers said.

“These processes increased inequality by operating on both ends of the wealth distribution, increasing the holdings of the rich while decreasing the holdings of the poor,” said researchers.

Christian Peterson, associate professor of anthropology in the College of Social Sciences at UH Mānoa and a member of the research team, added that a few of the Old World societies studied did not, however, utilize draft animals until well after inequality was already on the rise.

“Some of the sites we examined from northern China showed evidence of wealth differences on par with those from the near east and Europe thousands of years before the use of animal traction in agriculture. Pigs were the primary domestic animal at the time, and differences between families in the number of pigs raised for food seem likely to have contributed to the development of wealth inequalities there,” Peterson said.

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