Piles of human bones burned and boiled, smashed and scraped. Cooking pots smeared with blood. A few years ago, anthropologists in the American Southwest uncovered the grisly remains of what appeared to be an ancient cannibal feast, but they lacked the biological proof - until now.
Laboratory tests on some of the artifacts, including a piece of human excrement, have revealed traces of a human protein that scientists say is the first direct evidence of cannibalism among the Anasazi, whose empire stretched into present-day Colorado, Arizona, New Mexico and Utah.
''This proves they put the meat in their mouths,'' said Richard Marlar, a molecular biologist at the University of Colorado Health Sciences Center in Denver who developed the biochemical tests to detect the protein. ''If you didn't eat human beings, this protein would not show up.''
The excavation site, consisting of three collapsed pit dwellings nicknamed Cowboy Wash near Dolores, Colo., was occupied about 1150 A.D. It was abandoned after seven people were butchered there.
The findings were published in Thursday's issue of the journal Nature.
Other anthropologists said the protein evidence is convincing. However, it doesn't explain exactly who committed the cannibalism or why.
Nor does it demonstrate that the Anasazi commonly ate their own, whether for nourishment or in a religious ritual.
''I doubt it was a routine thing at all in the culture of the early pueblo people, any more than it was routine in any other culture,'' said anthropologist William Lipe of Washington State University.
Among modern-day Indians of the Southwest, leaders of the Hopi, Zuni and other tribes have been especially critical of cannibalism research.
But Terry Knight, a Ute Mountain Ute tribal leader who supervised the excavation, said of the findings: ''Like any other civilization, there were good, productive people, and there were bad people.''
Knight said he hopes the evidence of cannibalism will force anthropologists to revise their thinking about the Anasazi culture. He said ancient Indian culture is too often treated in simplistic terms when it was in reality complex, with many different tribes.
Cowboy Wash was one of about 10 Anasazi homesteads in the Four Corners region. Today's inhabitants, the Utes, commissioned archaeologists to conduct a scientific survey before installing an irrigation system.
Even without the specter of cannibalism, the Anasazi are a mysterious lost culture. They built an elaborate network of roads and ceremonial centers throughout the Southwest after 700 A.D. that were keenly oriented to the heavens. Severe drought helped to disperse the society by 1300 A.D.
Forty miles east of Cowboy Wash stands Mesa Verde, now an elaborate ghost city protected by cliffs and served by aqueducts. But most Anasazi lived in hardscrabble settlements, growing corn and hunting game.
The pit dwellings at Cowboy Wash appear to have been heavily used for many years, then suddenly abandoned. They contained pots, grinding stones, jewelry and other valuables.
In the ruins, researchers also found seven dismembered skeletons in 1994. The bones had been stripped of their flesh, then roasted and cracked for their fatty marrow. Skulls were scorched and cracked open for their brains. In the center of one cooking hearth was found a coprolite, or piece of dried feces.
The scene suggested a gruesome butchering, but critics complained the evidence was circumstantial. In 1997, Marlar offered to find biochemical proof.
In a series of tests, he determined that both the coprolite and residue on cooking pots contained human myoglobin. It is a protein that picks up oxygen from the bloodstream and carries it into the muscle cells.
Myoglobin is found in flesh, not in most organs or vessels. In mammals, the myoglobin of each species has its own chemical fingerprint. Marlar failed to find the myoglobin for deer, rabbit and other local game in the same samples.
As a comparison, he did not detect human myoglobin in coprolites and other artifacts found at other Anasazi sites from the same period.
''All we have found from the Cowboy Wash samples is human myoglobin - no other species,'' Marlar said. ''They had a human meat meal.''
Initially, researchers believed the victims might be prisoners of war who were sacrificed. Others contend the victims might have been executed and incinerated as witches, but not necessarily consumed.
The Cowboy Wash investigators now are developing a new scenario. According to University of North Carolina archaeologist Brian Billman, who coordinated the excavation, drought gripped the area in 1150 and the social order frayed. Marauders probably terrorized and cannibalized the families living at Cowboy Wash.
Billman described the coprolite as ''a final insult'' by the killers.
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On the Net:
Nature magazine: http://www.nature.com
Mesa Verde National Park: http://www.nps.gov/meve
Crow Canyon Archeological Center: http://www.crowcanyon.org
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EDITORS: Associated Press writer William McCall contributed to this story.