Why Are The World’s Oldest Mummies Turning into ‘Black Ooze’?

After the first few thousand years, you’d think you wouldn’t have to worry about perfectly preserved mummies going bad. After all, if they’ve made it that long, why wouldn’t they stand the test of time for much longer?

Apparently, that’s not the case here. The world’s oldest mummies, preserved for 7,000 long years, have started to rot and turn into “black ooze,” scientists say.

The Chinchorro were a group of hunter-gatherers who occupied the modern-day area of Chile and Peru millennia ago and began mummifying their dead at least 2000 years before the ancient Egyptians started the same practice, according to a Harvard release. Some of the oldest of their mummies, and in fact the oldest in the world, date all the way back to about 5050 BC.

But over the last decade, some of these mummies have started to decay rapidly and their skin has begun to go “black and become gelatinous.”

Marcela Sepulveda, a professor of archaeology at the University of Tarapacá, said in Harvard’s news release, “In the last 10 years, the [deterioration] process has accelerated. 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.”

To that end, scientists have figured out the cause of the decay.

Ralph Mitchell, a biology professor at Harvard was contacted by the Chilean University of Tarapacá’s archeological museum, where 120 of these mummies’ are housed, to test their skin.

He and his team found an opportunist bacterium has begun to live and thrive on the remains of these bodies and is now causing the decay.

These microbes are normal bacteria that live on people’s skin, so they’re not new, says the professor, but he explains they’re starting to grow at an accelerated rate now because of an environmental change that is taking place.

“The key word that we use a lot in microbiology is opportunism,” Mitchell said in the release. “With many diseases we encounter, the microbe is in our body to begin with, but when the environment changes it becomes an opportunist.”

In this case, the environmental change has to do with the higher humidity in the usually-arid area where the mummies are. These microbes thrive in humid conditions, and now possibly because of climate change, their presence has become a threat to the mummies.

The museum has to now work towards keeping these bodies in the right humidity and temperature conditions or risk “the native microorganisms […] chew these guys right up” Mitchell said to LiveScience.

If the mummies are not kept in the right humidity and temperature conditions, “the native microorganisms are going to chew these guys right up,” Mitchell told Live Science.

Mitchell’s new research will allow the University of Tarapacá’s archeological museum to better care for the ancient mummies.

Feature Image courtesy of Vivien Standen