Saving the World’s Oldest Mummies From Rot in a Warmer, Wetter World

Why are the ancient bodies of the Chinchorro people stored in a Chilean museum rapidly degrading into black ooze?

Chile Mummy
A mummified corpse of a Chinchoro girl between 4,000 and 8,000 years old gets a cleaning. George Steinmetz/Corbis

In Arica, Chile, the University of Tarapacá’s archaeological museum houses nearly 120 mummies, some of which are the oldest purposefully preserved bodies on earth. They come from the ancient Chinchorro peoples, who once lived across modern Peru and Chile and who preserved their dead through an elaborate process that involved covering the body and face in a thick paste made of ash, protein and water. Certain specimens date as far back as 5050 B.C., centuries before the first ancient Egyptian mummy. 

But recently a troubling mystery began to unfold at the museum. According to Harvard's School of Engineering and Applied Sciences, researchers noticed that many of the mummies were beginning to visibly degrade and producing a strange black goo. So the museum turned to outside experts in hopes of finding the cause of the rot and a way to prevent it.

Included in the effort was Ralph Mitchell, a Harvard biologist known for his work identifying causes of decay. Together with his team, Mitchell set to work evaluating and isolating the microbes on samples of both the preserved and decaying skin. The team cultured the organisms and then tested their effect on surrogate samples of pig skin in different conditions.

What they discovered were "opportunistic" microbes that typically live on people’s skin. When activated by moisture, these microbes chow down on dead tissue. But why had the bacteria only begun to cause problems over the last ten years?

The answer, according to Marcela Sepulveda, a professor of archaeology at the University of Tarapacá, may be found in Earth’s changing climate. Arica is located right next to the Atacama Desert, one of the driest deserts in the world. But recent changes in weather patterns have brought fog to the region, increasing the area’s moisture level.

The air in the museum is more humid, too, and that's given the microbes an opportunity to feast on mummy remains. To prevent the decay, the museum is now keeping humidity levels between 40 and 60 percent and is conducting further investigations into the affect of light and temperature on the bodies.

But there’s a larger problem scientists now hope to solve: As climate change continues, is there a way to help prevent the bacterial destruction of the possibly hundreds of Chinchorro mummies still buried throughout the region? The answer won’t come easy. In the meantime, the future of the undiscovered ancient dead and their artifacts will depend on humidity’s whim.

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