Having survived 8,000 years, the Chinchorro mummies found in modern-day Chile and Peru have started decaying more quickly than ever before—in some cases even melting into gelatinous "black ooze." Scientists at Harvard think they've found the reason why.


The mummies, the oldest manmade ones in the world, originate with the Chinchorro people, who preserved their dead by filling the bodies with fiber and straw. Unlike the Egyptians, the Chinchorro mummified all of their dead. Hundreds of these mummies are still buried in Chilean valleys, where they are often uncovered by construction.

The decaying problem began with the mummies that should be been kept most safe—inside the University of Tarapacá's archeological museum. Curators noticed the decay accelerating over the past decade. So they decided to bring in Harvard scientists who determined that the cause was bacteria. But the mummies had survived thousands of years already. Why did bacteria suddenly take a liking to them now?


A complete Chinchorro mummy.

The team took bacterial samples from degraded and non-degraded mummy skin and grew them in a lab. At higher humidity, skin with bacteria growing on them degraded more quickly, with decay setting in after just 21 days, according to a Harvard press release. That's where it clicked: Humidity has been rising in the city of Arica, where the archeologist museum is located.

The ideal humidity for the mummies turns out to be between 40 and 60 percent. Too high and they rot; too low and acidification can happen. That's good to know for a museum with climate control, but a changing climate could spell doom for the hundreds of mummies still out there in the ground. They have survived for so long, but they may not survive the humidity[Harvard]

Photo credit: Vivien Standen/Harvard

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