Ancient Chaco Canyon population likely relied on imported food

December 29, 2016, University of Colorado at Boulder
Ancient inhabitants of Chaco Canyon likely had to import corn to feed the masses a thousand years ago says a new CU-Boulder study. Credit: NPS

The ancient inhabitants of New Mexico's Chaco Canyon, the zenith of Pueblo culture in the Southwest a thousand years ago, likely had to import corn to feed the multitudes residing there, says a new University of Colorado Boulder study.

CU Boulder scientist Larry Benson said the new study shows that Chaco Canyon - believed by some archeologists to have been populated by several thousand people around A.D. 1100 and to have held political sway over an area twice the size of Ohio - had soils that were too salty for the effective growth of and beans.

"The important thing about this study is that it demonstrates you can't grow great quantities of corn in the Chaco valley floor," said Benson, an adjunct curator of anthropology at the University of Colorado Museum of Natural History. "And you couldn't grow sufficient corn in the side tributaries of Chaco that would have been necessary to feed several thousand people.

"Either there were very few people living in Chaco Canyon, or corn was imported there."

A paper by Benson was published online in the Journal of Archaeological Science: Reports.

Between the ninth and 12th centuries, Chaco Canyon (officially the Chaco Culture Natural Historic Park) located in the San Juan Basin in north-central New Mexico was the focus of an unprecedented construction effort, said Benson. At the height of its cultural heyday, 12 stone masonry "great houses" and other structures were built there, along with a network of ceremonial roads linking Chaco with other Pueblo sites in the Southwest.

As part of the study, Benson used a tree ring data set created by University of Arizona Professor Emeritus Jeff Dean that showed annual Chaco Canyon precipitation spanning 1,100 years. The tree rings indicate the minimum amount of annual precipitation necessary to grow corn was exceeded only 2.5 percent of the time during that time period.

Benson suggests that much of the corn consumed by the ancient people of Chaco may have come from the Chuska Slope, the eastern flank of the Chuska Mountains some 50 miles west of Chaco Canyon that also was the source of some 200,000 timbers used to shore up Chaco Canyon masonry structures. Between 11,000 and 17,000 Pueblo people are thought to have resided on the Chuska Slope prior to A.D. 1130, he said.

Winter snows in the Chuska Mountains would have produced a significant amount of spring snowmelt that was combined with surface water features like natural "wash systems," said Benson. Water concentrated and conveyed by washes would have allowed for the diversion of surface water to irrigate large corn fields on the Chuska Slope, he said.

Benson said the Chaco Canyon inhabitants traded regularly with the Chuska Slope residents, as evidenced by stone tool material (chert), pottery and wooden beams.

"There were timbers, pottery and chert coming from the Chuska region to Chaco Canyon, so why not surplus corn?" asks Benson, a former U.S. Geological Survey scientist.

Many archaeologists are still puzzled as to why Chaco Canyon was built in an area that has long winters, marginal rainfall and short growing seasons. "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."

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Mark Thomas
3.7 / 5 (3) Dec 29, 2016
Regarding Chaco Canyon, "I don't think anyone understands why it existed," Benson said.

If neighboring tribes are stronger and extremely aggressive, then moving away to uncontested land might make a lot of sense.
5 / 5 (1) Dec 30, 2016
Reminds me a bit of the Nabataean capital Petra. It was constructed in a place where they could construct an artificial oasis, but the population of the capital far exceeded what they could grow in the valley.
1.8 / 5 (5) Dec 30, 2016
Without wheel or horses, the daily transportation of all that food using people and dogs dragging sledges must have been a real burden.

Perhaps all those people did not live there at the same time, and each new set would build new buildings.
not rated yet Dec 30, 2016
I imagine the place was held in reverence for religious reasons.
5 / 5 (1) Dec 31, 2016
Yes believe it was selected for the particular gypsum salts for art. Yes, most of the rooms were occupied only seasonally, Yes, most were storage rooms for water. Possibly the climate drenched the highlands continually so there was significant flow to the valley.
Dec 31, 2016
This comment has been removed by a moderator.
5 / 5 (1) Dec 31, 2016
This is consistent with the theory that the people of Chaco Canyon were the religious leaders of the region and that the rest of the population brought food and offerings (tithes?) to Chaco. And if Chaco were also the government capital, then that would also be an explanation. (I live in Washington DC, and our metropolis is entirely dependant on tax revenues sent to us from the rest of the country in return for "government services".)
2 / 5 (4) Dec 31, 2016
I understand they have recently found tracks of taco trucks from that era, . . .
5 / 5 (2) Jan 02, 2017
Shakescene21: The same could be said of most large cities. Not tax revenue per se, but food. Most cities couldn't feed themselves, but the advantages of having a large, diverse population in a small area outweighs the costs of food transport.

I wonder if information technology is going to change this in future, we're still living in the old city/hinterland system devised back when being in one place meant easier communication, but nowadays this is no longer the case.
not rated yet Jan 06, 2017
"Shakescene21: The same could be said of most large cities. Not tax revenue per se, but food. Most cities couldn't feed themselves, but the advantages of having a large, diverse population in a small area outweighs the costs of food transport."

@nkalanaga: Absolutely yes. So, Chaco Canyon must have been part of a broader economy with some other region.

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