The 700 acres of earthen structures at Poverty Point, La., are one of the few monumental constructions on Earth built by hunters and gatherers as opposed to agricultural societies. Anthropologists recently estimated that the largest mound may have been built in a few months or less, approximately 3,200 years ago.

“We’re talking about an area of northern Louisiana that now tends to receive a great deal of rainfall,”  study co-author Tristam Kidder, anthropology chair at Washington University in St. Louis, said in a press release. “Even in a very dry year, it would seem very unlikely that this location could go more than 90 days without experiencing some significant level of rainfall. Yet, the soil in these mounds shows no sign of erosion taking place during the construction period. There is no evidence from the region of an epic drought at this time, either.”

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Piling the estimated 238,500 cubic meters of soil in the mound would require 3,000 laborers working full time, according to  the anthropologists’ recent estimate published in the journal Geoarcheology. Modern 10-wheel dump truck would need 31,217 loads to equal that amount, Kidder estimated.

“The Poverty Point mounds were built by people who had no access to domesticated draft animals, no wheelbarrows, no sophisticated tools for moving earth,” Kidder said. “It’s likely that these mounds were built using a simple ‘bucket brigade’ system, with thousands of people passing soil along from one to another using some form of crude container, such as a woven basket, a hide sack or a wooden platter.”

Modern hunter-gather societies are generally not large, rarely comprising more than a few dozen people. However, the rapid construction of the mounds suggests that ancient hunter-gathers were capable of sophisticated organization of large groups.

On the other side of the planet, the structures at Göbekli Tepe, Turkey may have been built by another hunter gather society in the process of developing a larger scale agrarian culture. Parts of Göbekli Tepe were already 8,000 years-old by the time Poverty Point was built. The largest earthen mound in North America, Monk’s Mound in Cahokia, Il., was built by an agricultural society approximately 2,000 years later than the Poverty Point mounds.

CREDIT: Mound A at the Poverty Point site, Louisiana, USA. (Kniemla, Wikimedia Commons)