Tuesday, October 14, 2003
Chaco Cornfields Far-Flung
By John Fleck
Journal Staff Writer
Ancient corn cobs found at Chaco Canyon were grown 50 or more miles away, according to new research, more evidence for the hypothesis that Chaco was the center of a widespread culture.
The corn might have been imported to feed a cadre of masons who built Chaco's great structures more than 800 years ago, a team of scientists reported Monday.
The scientists compared the corn's chemistry with soil at sites around the San Juan Basin, according to Larry Benson, a U.S. Geological Survey scientist based in Boulder, Colo.
Benson and his colleagues published the results of their research Monday in the Proceedings of the National Academy of Sciences.
Some of the corn they tested had been grown near present-day Newcomb, 50 miles to the west at the foot of the Chuska Mountains, the scientists found.
They also found corn that had apparently been grown on the Animas or San Juan river flood plains 50 miles to the north.
Located in northwestern New Mexico, Chaco Canyon sits at the center of what apparently was a widespread culture of pueblo dwellers from about 800 A.D. to the late 1100s.
But the massive "great houses" of Chaco, such as the famous 600-room Pueblo Bonito, have long seemed larger to scientists than the farmland around them could have supported.
"It looks like hell," Benson said of the arid land around Chaco.
Scientists in the 19th and early 20th centuries guessed it must have been substantially wetter when Chaco was inhabited, which would have allowed more farming in the area, explained Julio Betancourt, a U.S. Geological Survey scientist based in Tucson who has studied Chaco's ancient climate.
That belief, Betancourt said, turned out to be wrong. Research on ancient climate conditions ruled out a substantially wetter Chaco.
Archaeologists then turned to the idea that there was some sort of connection between the massive, centrally located Chaco Canyon structures and a host of other contemporary pueblos scattered across the San Juan Basin.
They think Chaco Canyon must have been a ceremonial or economic center, supported by crops and other goods coming from communities throughout the region.
Tools made from Chuska Mountain stone have been found in Chaco, and Betancourt and his colleagues discovered recently that logs used to build Chaco's buildings came from the Chuskas and other distant mountains.
The basic agricultural problem is that Chaco itself is too dry to reliably grow corn, which was the staple crop of the San Juan Basin Anasazi.
It takes a minimum of 6 inches of growing season rain per year, without irrigation, to grow corn. Chaco averages less than 5 inches per year during the growing season, Benson and his colleagues wrote, and the Chaco River does not provide reliable runoff.
Newcomb, located where Captain Tom Wash flows out of the Chuskas, is a different story, with more available water for farming and evidence of seven square miles of cornfields.
Similar conditions suggest farming would have been more productive along the San Juan and Animas rivers to the north, though modern farming has obliterated any archaeological evidence for it.
But while scientists have long hypothesized that corn cobs found in excavations at Chaco must have come from somewhere else, until now they have not been able to say where.
The new corn research adds to similar data published two years ago on the massive logs used as construction beams. Betancourt and a team of scientists used a similar technique to study the chemistry of the trees, showing the beams had come from afar from the Chuskas to the west and the area around Mount Taylor to the south.