Chaco Canyon was once host to several thousand people. By A.D. 1100, it was the pinnacle of Pueblo culture in the American Southwest. Yet, its soil was unable to support such a large population.

According to a new study published in the Journal of Archaeological Science: Reports, the people of Chaco Canyon must have relied on food surpluses from elsewhere.

"Either there were very few people living in Chaco Canyon, or corn was imported there," Larry Benson, an adjunct curator of anthropology at the University of Colorado Museum of Natural History, explained in a news release.

In addition to smaller pueblos, large stone masonry houses and other structures were being constructed in Chaco Canyon between the 9th and 12th centuries.

What supported such great wealth? Not a surplus of food. Analysis of tree rings suggests the region's rainfall totals during the time period wouldn't have been sufficient to coax beans or corn from the area's acidic soil.

Farming conditions were friendlier 50 miles to the west on the eastern flank of the Chuska Mountains, where snow accumulation and spring runoff bolstered crops. The mountain slopes and foothills also hosted a large population of people, who were known to have traded timber with the residents of Chaco Canyon.

"There were timbers, pottery and chert coming from the Chuska region to Chaco Canyon, so why not surplus corn?" Benson wondered.

The new research highlights the necessity of trade for those living in Chaco Canyon, but it fails to explain why so many people settled so far from sufficient sustenance.

"I don't think anyone understands why it existed," Benson said. "There was no time in the past when Chaco Canyon was a Garden of Eden."