The world 's oldest mummies buried more than 7,000 years ago in the arid desert of northern Chile are being turned into black slime by climate change . Scientists have found that growing humidity can cause an explosion of bacteria living on the preserved skin of the Chinchorro mummies . The bacteria then feeds on the ancient skin , causing it to break down into a black slime . The preserved skin on the outside of Chinchorro mummies in Arica , northern Chile , have begun to rapidly degrade as bacteria and humid air is turning it into black slime , as can be seen in the photograph above . Researchers say that rising humidity levels in Arica , Chile , is putting the 120 Chinchorro mummies at the University of Tarapacá 's archaeological museum at risk . However , they warn that hundreds of other mummies buried just beneath the sandy surface in the valleys throughout the region are also under threat . While some of the earliest mummies found in the Atacama desert appear to have been the result of natural preservation in the extremely dry conditions , around 5,000 BC , the Chinchorro people began deliberately preserving their dead . Although the practice began 2,000 years before the Ancient Egptians began mummifying their own dead , the techniques used by the Chinchorro were often surprisingly sophisticated . They would often take the most care when preserving the remains of dead children and babies - suggesting the act had a deep significance with linking the living to the dead . First the Chinchorro would extract the brains and organs before then reconstructing the body with fibres . They would fill the empty skull with straw or ash . Reeds were then used to sew it back together and connect the jaw to the cranium . A stick was used to keep the spine straight and the skin was patched back together before being covered with a paste made from manganese , red ocher or mud . Professor Marcela Sepulveda , an archaeologist at the University of Tarapacá , said : 'In the last 10 years , the 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 . ' The Chinchorro mummies are in some cases nearly 4,000 years older than those found preserved from ancient Egypt . The oldest mummy discovered in the Atacama desert dates to 7020BC while the oldest in Egypt dates to 3,000BC . However , the practice of preserving the dead with mummification became popular among the Chinchoro around 5,000 BC , with children and babies often being the most elaborately preserved . The Chinchorro were a prehistoric people who lived in scattered communities and used fishing to help them survive on the desert coast of Chile and Peru . It is thought they began preserving their dead though mummification as part of a religious act designed to bridge the world between the living and the dead . An estimated 282 mummies have now been recovered from the dry , sandy soil in the region , but scientists say there could be hundreds more buried there . Preserved corpses are often found as the shifting sand exposes their bodies . Arica and the surrounding Atacama Desert is one of the driest places in the world and the town receives less than 0.02 inches of rain a year . The skin on the head of this Chinchorro mummy at the San Miguel de Azapa Museum in Arica , Chile has begun to break down due to the damage being caused by bacteria growing as humidity in the area increases . The mummies were found buried in the arid desert valleys around Arica in northern Chile , shown on the map . It is this dry climate that has helped preserve the mummies for more than 7,000 years . However , the region has been growing slowly damper in recent years . Scientists at the University of Tarapacá museum first noticed black slimy patches appearing on the preserved skin of the Chinchorro mummies around ten years ago . As time has gone on they have degraded at 'an alarming rate ' as the preserved skin has broken down into a black slime . Researchers at Harvard School of Engineering and Applied Sciences have now conducted a series of tests to find out what was causing the degradation . They found that bacteria normally found growing on the human skin appeared to become 'supercharged ' when placed on mummy skin in high humidity . They found that mummies need to be kept at between 40 per cent and 60 per cent humidity to prevent degradation occurring . Some of the Chinchorro mummies , like the one above buried in a coffin made from reeds , show highly sophisticated preservation thousands of years before mummification began to be used in ancient Egypt . If humidity falls below this level , acidification could also damage the mummies . Museum staff are now fine tuning the temperature and humidity to help preserve the mummies in their extensive collection . Professor Ralph Mitchell , a biologist at Harvard who led the work , said : 'We knew the mummies were degrading but nobody understood why . 'This kind of degradation has never been studied before . 'With many diseases we encounter , the microbe is in our body to begin with , but when the environment changes it becomes an opportunist . ' Professor Mitchell and his colleagues are now keen to find ways to help protect the mummies still preserved out in the desert .
Hundreds of mummies preserved and buried by ancient Chinchorro people have been found in the arid sand of the Atacama Desert in northern Chile . In the past ten years black wet patches have appeared on some mummies . Scientists found bacteria on preserved skin is breaking the mummies down . Rising humidity levels in the region have 'supercharged ' the skin bacteria . They are then causing the preserved skin to break down into black slime . Scientists now hope to protect the mummies from suffering further damage .