©Fernando Vergara/Associated Press

A skeleton emerges from the soil of an ancient grave, one of nearly a thousand tombs recently found in a neighborhood in Bogotá, Colombia.

Builders clearing land for a housing project in Colombia have uncovered an ancient burial site containing nearly a thousand tombs linked to two little-known civilizations.

The site covers some 12 acres (5 hectares) in the impoverished Usme district in southeast Bogotá and includes one set of remains that some researchers believe could be a victim of human sacrifice.

The possible victim is a young woman who seems to have been buried alive, said Ana Maria Groot, one of the lead anthropologists from the National University of Colombia working at the site.

"Her mouth is open as if in terror, and her hands seem contracted as if she had tried grabbing hold of something," Groot said.

Another tomb contains the remains of a man with a curved tibia, or shinbone, possible evidence that the man was a shaman, she added.

Spanish observers in the 1500s wrote of indigenous shamans spending long periods in caves with no exposure to sunlight. A lack of sunlight would produce a shortage of vitamin D, causing curving of the bones, explained Groot's colleague, Virgilio Becerra.

Two Mysterious Cultures

Aside from such unusual finds, the site is unique for its age and length of occupation, the anthropologists say.

The tombs range in date from around the first century to the 16th century A.D., based on analysis of pottery found with the remains.

The first 500 years of the site's use date to the so-called Herrera period, when several small, obscure groups thrived in this region of the Andean highlands during the development of agriculture.

"The agriculture became more intensive, more systematic at this time," Groot said.

"We have high expectations about finding what kinds of plants they cultivated."

From around A.D. 500 to 1500, the site seems to have been occupied by the Muisca, another culture that is one of Colombia's most important but least understood civilizations, Groot said.

Rife with artifacts from both periods, the Usme site is a potential treasure trove of information, she added.

"A settlement like Usme offers the chance to research the settlement's development through different moments in a prolonged occupation," she said.

"We can identify those changes as expressed in their cultural practices."

Ongoing analysis should reveal more about life expectancy, diet, disease, and other aspects of daily life and social organization in the settlement, Groot added.

Temple Site and Other Discoveries

Anthropologists also found ruins of a human settlement next to the burial site, including what may be evidence of a temple. Holes for posts suggest a large circular structure, Groot said.

Pottery found with the remains mostly includes fragments of decorative and simple pitchers, cooking pots, and cups.

The decorative pitchers combine geometric designs with images of animals such as frogs, birds, and snakes.

Researchers also found stones for grating or cutting vegetables and for grinding grain, though no evidence of the settlers' diet has yet been determined.

Local authorities are considering making the site into a museum.

Excavation began in January and will continue while anthropologists await results from radiocarbon sampling of human bones and other objects to determine their ages.

"Invaluable" Find

Guillermo Cock is an archaeologist and Andean expert whose work has been partly funded by the National Geographic Society, which operates National Geographic News.

He cautioned that apparent evidence of human sacrifice seen at Usme likely has other origins.

In the case of the young woman who looks to have been buried alive, her contracted hands may be explained by early arthritis, he said.

Likewise, her opened jaw may be the result of the body having been moved before or after burial, he said.

Nonetheless, the Usme site should prove "invaluable" to science, said Cock, whose work has helped unearth burial sites with thousands of tombs in Peru.

"Conservation [of graves and other archaeological material] in Colombia and Venezuela tends to be poor because of the soil's humidity, which quickly destroys organic remains," Cock said.

"If the period that each tomb belongs to can be identified, even if they are in a poor state, it would be an invaluable amount of information about this Muisca population."