SCIENCE / MEDICINE : Shadows of the Past : Scientists Work Against Time to Unravel Mystery of Vanished Civilization in Chaco Canyon
Deep within a barren, rocky, half-mile-wide canyon in northwestern New Mexico, a small army of scientists is working against time to solve the mystery of a long-vanished pre-Columbian civilization. There, multistoried buildings, elaborate waterworks and far-ranging road networks have challenged archeologists for more than a century.
The site is Chaco Canyon, 120 miles west of Santa Fe in the heart of the arid, desolate, 30,000-square-mile San Juan Basin of the Southwest.
For about two centuries, a civilization of up to 20,000 people demonstrated highly advanced engineering skills, building massive homes, roads and other facilities before vanishing. They left no written history and few skeletal remains.
But they did leave behind a major, puzzling question: How could a people so primitive in many ways be so advanced in others?
Between about AD 900 and 1115, even without the wheel or metal tools, Anasazi Indians built a community rivaling the pyramids of Egypt or the Great Wall of China in size and complexity. By one estimate, their nine massive stone “Great Houses” alone could have housed 50,000 people. The largest, the five-story Pueblo Bonito, covered three acres at the base of a 100-foot-high mesa and had walls three feet thick and more than 650 rooms.
Each house contained one or more kivas-- covered, circular underground ceremony rooms. These obviously served religious needs. Yet there is evidence that only a few of the other rooms in each house were ever used for living purposes such as cooking and sleeping, leading some scientists to speculate that the primary purpose of the elaborate ancient Pueblo community was more religious than utilitarian.
The size of the Great Houses suggests that a lot of people were needed to build and occupy them. Yet while a few scattered skeletons have been found in Chaco Canyon, a century of searching has unearthed not a single formal burial ground. Archeologists ponder: What happened to the remaining dead of the two-century civilization?
The Chacoans also built--or overbuilt, as some scientists put it--more than 400 miles of graded, curbed outlying roads, some wider than a modern two-lane road. Yet their builders did not have wheeled carts, so a narrow footpath would seem to have served as well. Nor did some of the roads seem to link important parts of the Chaco community. The most famous one, the Great North Road, for instance, runs north-south for 35 miles, over small hills rather than taking an easier route around them, ending at the edge of a wild, uninhabited canyon. It is, in the description of one scientist, a “road to nowhere.”
The Chacoans had no writing, no metallurgy and no plow--three factors without which a culture generally is considered “primitive.” Yet in many ways, suggests David Hurst Thomas, curator of anthropology at the American Museum of Natural History in New York, “the Chacoans were surprisingly advanced.”
They were, for example, accomplished astronomers. On Fajada Butte, for example, near one end of the canyon, “they carved a rock calendar so accurate the sun lights its center like a dagger at the summer solstice. And both their houses and their irrigation system displayed a superb knowledge of engineering.”
For a little more than two centuries, the Chacoans gathered in this remote place, tending their crops of corn, beans and squash with wooden sticks in meager, marginally productive soil. Then, inexplicably, they abandoned everything around AD 1115, never to return. Why they left is just one of the many puzzles left unsolved.
The ruins were discovered in 1849 by a U.S. Army expedition led by Lt. James Harvey Simpson. In 1895, Richard Wetherill, an archeologist with the then-new Smithsonian Institution, led the first of many archeological expeditions. By far the biggest effort was the Chaco Project, an interdisciplinary study that began in 1972 under co-sponsorship of the National Park Service, which has administered the site as a national historic park since 1907, and the University of New Mexico. Before the project ended 10 years later, scientists had inventoried more than 2,500 sites in the canyon and outlying area, excavated 27 of them and recovered more than 300,000 artifacts.
The artifacts furnish many pieces in the Chaco jigsaw puzzle. Carved wooden figures of birds, horns, hoops and prayer sticks found in just one of the Great Houses, Chetro Ketl, underscore the religious nature of the settlement, for instance. Turquoise from the Santa Fe area and shells from the West Coast suggest its far-flung regional nature. And items such as Mexican copper bells strengthen the belief that the Chacoans had strong cultural and trade ties with their pre-Columbian neighbors to the south.
Scientists, trying to sort out what it all means, are still poring over 10,000 pages of research into Project Chaco, which ended in 1972. Meanwhile, new research is being conducted into specific parts of the Chaco story. “One thing is certain,” says Bonnie Wilson, National Park Service interpretive officer at Chaco Culture National Historic Park. “For every question that’s been answered, there seem to be two more waiting to be asked.”
There’s a sense of urgency for the latest research. Time is taking its toll at Chaco Canyon. Many of the buildings and artifacts are fading after a millennium of wind and rain.
Later this summer, Dr. Robert Vallier of the University of Tennessee will lead a team of researchers to study and catalogue rock art (“picked” or painted designs) at about 100 sites in the canyon. A specialist in semiotics--the science of symbols--Vallier notes that rock art is the closest thing to a written history left behind by the Chacoans.
“It isn’t Cezanne or Picasso but it tells us a lot about any people,” he says. “And after about 1,000 years, some of the best examples here are fading fast.”
Some of the canyon’s wood, too, is deteriorating. There is a lot of it; by one estimate, the Chacoans cut more than 215,000 trees for roofs, beams and floors. “A lot of what’s left must be preserved for study,” says Dabne Ford, who is directing a Wood Preservation Project funded by the NPS. “Tree-ring dating is one of the best methods of pinpointing important dates and events in the Chacoan period. Once that wood is gone, we’ll lose the most valuable clues to such questions as where the trees were cut and how far they were hauled. Most important is when it was cut; we’ve been able to pinpoint some cuttings down to not only the year, but the year and month.”
Ford’s preservation project is now in its fourth year. So far, more than 6,000 samples of wood have been removed from their sites. Some were sent to a laboratory for tree-ring analysis; tree rings not only are used to date trees, they also provide clues to long-term weather cycles such as prolonged droughts--valuable in determining possible reasons why the Chacoans abandoned their ancient pueblos.
In Washington, Anna Sofaer is as concerned with the religious and ceremonial aspects of Chacoan life. An artist and photographer, she is president of the Solstice Project, a privately funded, nonprofit group formed in 1978 to study, document and preserve the remarkable Chaco sun dagger discovered atop Fajada Butte at the summer solstice a year earlier. The dagger represents a celestial calendar of the ancient Chacoans--ancestors of today’s Pueblo Indians--and marks, in addition to both winter and summer solstices, the 19-year cycle of the moon as well.
Since finding the dagger, Sofaer’s group has widened its study to other facets of the Chaco complex that suggest that religion played a far greater role in its establishment than was once believed. Thousands of remote imaging photographs from both airplanes and satellite, for instance, have accurately defined the linear design of many of the buildings and roads in the canyon and beyond. This information suggests how the ancient Indians relied on lunar and solar phenomena and, in turn, how the sun and moon figured into Anasazi religion. Even among their descendant Pueblo Indians of today the sun is considered the source of life itself.
How many people lived permanently in Chaco Canyon? Although figures ranging from 6,000 to 20,000 have been suggested, a maximum of 2,000 may be closer to the truth. That is the figure offered by Stephen H. Lekson, a visiting scholar at the Arizona State Museum in Tucson who was a principal investigator in the Chaco Project.
But as continuing research scales down the population estimate, it has enlarged the view of the canyon as a vast regional religious center and the physical size of the Chaco complex in general.
“Given a dramatic increase in the scale of the Chacoan system,” Lekson concluded in a paper delivered last year, “we must reevaluate our hypothesis. . . . It is clear that the picture now emerging signals the beginning of a new generation of Chacoan studies.”
