A burial of a young woman found in the middle of a tomb in Peru's Cotahuasi Valley, where dozens of mummy-filled tombs were discovered.

Dozens of tombs filled with up to 40 mummies each have been discovered around a 1,200-year-old ceremonial site in Peru's Cotahuasi Valley.

So far, the archaeologists have excavated seven tombs containing at least 171 mummies from the site, now called Tenahaha.

The tombs are located on small hills surrounding the site. "The dead, likely numbering in the low thousands, towered over the living," wrote archaeologist Justin Jennings, a curator at Toronto's Royal Ontario Museum, in a chapter of the newly published book "Tenahaha and the Wari State: A View of the Middle Horizon from the Cotahuasi Valley" (University of Alabama Press, 2015).

Before rigor mortis set in, the mummies had their knees put up to the level of their shoulders and their arms folded along their chest, the researchers found. The corpses were then bound with rope and wrapped in layers of textiles. The mummies range in age from neonate fetuses to older adults, with some of the youngest mummies (such as infants) being buried in jars. While alive the people appear to have lived in villages close to Tenahaha. [See Photos of the Peru Mummies and Tenahaha Site]

Bits and pieces of mummies

The mummified remains were in poor shape due to damage from water and rodents. Additionally, the researchers found some of the mummies were intentionally broken apart, their bones scattered and moved between the tombs. In one tomb the scientists found almost 400 isolated human remains, including teeth, hands and feet.

"Though many individuals were broken apart, others were left intact," Jennings wrote in the book. "People were moved around the tombs, but they sometimes remained bunched together, and even earth or rocks were used to separate some groups and individuals." Some grave goods were smashed apart, while others were left intact, he said.

Understanding the selective destruction of the mummies and artifacts is a challenge. "In the Andes, death is a process, it's not as if you bury someone and you're done," Jennings told Live Science in an interview.

For instance, the breakup and movement of the mummies may have helped affirm a sense of equality and community. "The breakup of the body, so anathema to many later groups in the Andes, would have been a powerful symbol of communitas (a community of equals)," wrote Jennings in the book. However, while this idea helps explain why some mummies were broken up, it doesn't explain why other mummies were left intact, Jennings added.

A changing land

Radiocarbon dates and pottery analysis indicate the site was in use between about A.D. 800 and A.D. 1000, with the Inca rebuilding part of the site at a later date.

Tenahaha, with its storerooms and open-air enclosures for feasting and tombs for burying the dead, may have helped villages in the Cotahuasi Valley deal peacefully with the challenges Peru was facing. Archaeological research indicates that the villages in the valley were largely autonomous, each likely having their own leaders.

Research also shows that between A.D. 800 and A.D. 1000 Peru was undergoing tumultuous change, with populations increasing, agriculture expanding and class differences growing, Jennings said. At sites on the coast of Peru,archaeologists have found evidence for violence, with many people suffering cranial trauma (blows to the head), Jennings said. In some areas of Peru, scientists have found pottery containing drawings of fanged teeth and human trophy skulls (skulls that could have been taken in battle) the researchers note.

At Tenahaha, however, there is little evidence for violence against humans, and pottery at the site is decorated with what looks like depictions of people smiling, or "happy faces," as archaeologists referred to them. [Fight, Fight, Fight: The History of Human Aggression]

Tenahaha may have served as a "neutral ground" where people could meet, bury their dead and feast. As such, the site may have helped alleviate the tensions caused by the changing world where these people lived, Jennings said.

"It's a period of great change and one of the ways which humans around the world deal with that is through violence," Jennings said in the interview. "What we are suggesting is that Tenahaha was placed in part to deal with those changes, to find a way outside of violence, to deal with periods of radical cultural change."

Excavations at the site were carried out between 2004 and 2007 and involved a team of more than 30 people from Peru, Canada, Sweden and the United States.

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