March 10, 2015
Something is eating 7,000-year-old mummies
An ancient people living along the coasts of modern-day Chile and Peru called the Chinchorro are the first-known population of human to practice mummification, around 5050 BC, and quite a number of the mummies have been uncovered over the years.Recently, Chinchorro mummy specimens in Chilean museums have begun to degrade at an alarming rate, sparking scientists to scramble in search of a reason and a way to halt the degradation.
“In the last ten years, the process has accelerated,” said Marcela Sepulveda, professor of archaeology at the University of Tarapacá, which houses numerous Chinchorro mummies. “It is very important to get more information about what’s causing this and to get the university and national government to do what’s necessary to preserve the Chinchorro mummies for the future.”
With some of the mummies turning to black ooze, Chilean anthropologists turned to their colleagues at the Harvard School of Engineering and Applied Sciences (SEAS).
“We knew the mummies were degrading but nobody understood why,” said Ralph Mitchell, a professor of applied biology at SEAS. “This kind of degradation has never been studied before. We wanted to answer two questions: what was causing it and what could we do to prevent further degradation?”
The mummification process
Sepulveda explained that the 7,000-year-old process was painstaking and time-consuming. The Chinchorro would first draw out the brains and internal organs, then stuff the body with fiber, fill up the cranium cavity with straw or ash and use reeds to sew it together again, including hooking up the jaw to cranium. A stick maintained the backbone and tethered it to the skull. The embalmer then repaired the skin, at times patching the body using the skin of sea lions or other animals.
Finally, the mummy was engrossed in a mixture, the color in which archeologists allocate to various eras in the over 3,000 years of Chinchorro mummy-making: black made from manganese was used in the most ancient ones, red made from ocher in later examples, and brown mud had been applied to the newest specimens.
Saving mummy dearest
The researchers began their work by taking both degrading skin and undamaged skin from mummies in the museum’s collection. The team quickly determined that microbes were behind the degradation.
“With many diseases we encounter, the microbe is in our body to begin with, but when the environment changes it becomes an opportunist,” Mitchell said. “Is the skin microbiome from these mummies different from normal human skin? Is there a different population of microbes? Does it behave differently? The whole microbiology of these things is unknown.”
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Next, the team isolated microbes from both the degrading and uncompromised skin. The researchers then cultured the organisms in the lab and used pig skin surrogates to see what happened when the samples were exposed to several humidity levels. The team saw that the pig skin samples began to break down after 21 days at high humidity, and the team was able to duplicate the results using mummy skin.
This result was consistent with the increasing humidity levels in the region where the archeological museum is located, the researchers said.
The international team said properly regulating the conditions in the museum should help to preserve the excavated mummies, but the team also expressed concern that mummies still in the field are vulnerable.
“What about all of the artifacts out in the field?” Mitchell asked. “You have these bodies out there and you’re asking the question: How do I stop them from decomposing? It’s almost a forensic problem.”