Some 1,400 years later, their handprints are still visible in El Salvador's soil.

The people of Ceren had just harvested their crops of manioc, also known as cassava, a calorie- rich tuber with 10 times the per-acre energy content of rice and beans. The beds had been replanted with manioc stalks to regenerate bushes for the next growth cycle when the Loma Caldera volcano erupted, destroying the village and burying the manioc field 10 feet deep.

The volcanic ash actually made images of hand-shaped dirt, indicating the stalks were planted "just hours before the eruption," said Payson Sheets, professor of anthropology at the University of Colorado.

It's the first time an archaeology team has ever found evidence of cassava cultivation in the New World.

"Finding this field was sort of a jackpot for us," said Sheets, who led the team of CU researchers and students.

Manioc's extraordinary productivity may help explain how the Maya could have supported such dense populations at Tikal in Guatemala and Copan in Honduras, Sheets said.

Sheets had been searching for manioc in the New World since 1966, when Ben Bronson, with the Field Museum in Chicago, first wrote that manioc might be the crucial but undiscovered food that sustained large populations.

"We knew that the slash-and- burn agriculture with corns and beans just couldn't sustain a large population," Sheets said.

It's more proof that the lives of some ancient Central American farmers weren't the hand-to- mouth existences once thought, Sheets said.

"The common view had been that their lives were drudgery, a rather boring blue-collar life," he said. But the discoveries at Ceren have made us go, 'Wow.'

"From the quality of their houses, the diversity of their food, the fact that a quarter of their pottery is multi-hued and brought in from 150 kilometers away ... they were doing great.

"Clearly, they had a surplus of food to exchange" for other goods.

Monday, Bronson e-mailed Sheets with congratulations: "Amazing. I never thought that such conclusive physical evidence would ever be found. "Congratulations. The stem and the tuber are both beautiful. The excavator who found it was on his/her toes. Not many archaeological laborers would have recognized it as being worth keeping."

Sheets has been directing excavation at Ceren since its discovery in 1978.

It's considered the best preserved site in Latin America because the volcano froze history in time, giving a unique view of life among the ancient farmers.

"Once again, we felt we were right on the heels of these ancient people because of the exquisite preservation" provided by the volcanic ash.

The CU team already had determined that the eruption happened on an evening in early August - based on the height of the corn stalks and the fact that the farm tools had been brought inside, but the sleeping mats hadn't yet been rolled out.

Ceren is believed to be better preserved even than Pompeii, the Roman town buried by Mount Vesuvius in Italy.

One mystery of Ceren is why no people have been found. But the recent discovery of a fault line indicates that an earthquake may have preceded the volcano, giving villagers just enough time to flee, while leaving pottery, homes and the rich prehistoric past behind.

The National Geographic Society funded the 2007 CU research effort at Ceren. It's the most recent of five research grants made by the Society to Sheets and his students.

scanlon@RockyMountainNews.com or 303-442-8729