They conclude in the Journal of Anthropological Archaeology that elite social classes in societies as diverse as ancient Mesopotamia, the American Midwest and Late Bronze Age Europe were competitive with each other, engaging in conspicuous consumption, including larger and larger mortuary mounds for their leaders over time.
"As social complexity increased, mound sizes tended to increase as well. But what was surprising was how variable it was based on region. Some places, like Poverty Point in Louisiana, have some of the largest prehistoric earthen architecture in the world, but they aren't the earliest mounds of the Americas. Mounds in the Mississippi River Valley grew gradually over time, even though the societies there were highly complex fairly early in their history," says Carr.
In Poverty Point, the largest earthen mounds were built about 1150 BCE, while nearby Watson Brake had smaller but earlier constructions. In contrast, Cahokia in Illinois saw a gradual increase in mound sizes over a long period, from about 100 BCE to CE 1350.
The researchers found other instances where mound-building was not associated with the largest centers. For example, in the Indus Valley of modern-day Pakistan and India, small, early mound centers gave way to larger, later settlements without mounds at all.
"We also found that burial mounds, like other forms of conspicuous consumption, did not occur in all societies. In general, smaller, more egalitarian societies did not build mounds. They appear to be mostly a feature of larger scale societies," says Carr.
Carr hopes to expand the study to analyze a larger sample of mound sites and mortuary practices from a broader range of societies. By including additional archaeological and paleoecological data, the study might identify environmental factors that influenced the development of mortuary mounds and conspicuous consumption.
