Colorful bodies painted in vibrant reds or blacks, heads dressed in wigs of human hair, and masks with eyes and mouths wide open, as if still breathing – these were the mummies made by the Chinchorro people.

They were among the earliest ancient humans to settle on what’s now the coast of northern Chile and southern Peru. And the mummies are the oldest in the world, predating even the first mummified pharaohs of Ancient Egypt by a couple millennia.

But after thousands of years, Chinchorro mummies are beginning to decay. As experts work to save these cultural relics, they’re not only preserving a vital part of Chilean heritage, but also the memory of the Chinchorro society.

Are Chilean Mummies Decomposing?

Despite having lasted multiple centuries preserved in the arid desert, Chinchorro mummies began to degrade in recent decades – and rapidly.

It started with the black ooze, observed in the mummy collection at the San Miguel de Azapa Archaeological Museum, which is affiliated with the University of Tarapacá. Observations of increasing regional humidity over the years suggest that climate change was linked to the decay.

What Is Causing the Chinchurro Mummies to Decay?

A team of experts, including Ralph Mitchell, a microbe sleuth of sorts from Harvard University, took to unraveling this mystery.

Mitchell and research assistant Alice DeAraujo isolated all the microbes from samples of Chinchorro mummy skin and incubated them on pig skin. They monitored the samples at three ranges of humidity over 21 days and found that degradation in both pig and Chinchorro skin increased with humidity levels.

Humidity, wrote the authors in their published study, triggers microbial activity. In this case, it awakened opportunistic microbes, which are commonly found in our skin microbiome. The microbes then began chomping down on the collagenous proteins making up skin, leading to the observed decay.

This means that as waters warm and humidity levels rise on the Chilean coast, Chinchorro mummies, both those stored in museums and still buried in the desert, are in danger.

Read More: How Ancient Egyptians Preserved Bodies for the Afterlife

Who Were the Chinchorro?

The Chinchorro people were early fishers and hunter-gatherers that lived in the Atacama Desert, one of the driest regions in the world. Despite the hostile environment, thanks to the proximity of the Pacific Ocean, the Chinchorro survived and thrived on rich marine and terrestrial resources.

Rivers, like the Camarones River, were their main life sources, according to anthropologist Bernardo Arriaza, who works at the University of Tarapacá in Arica, Chile. Where there was fresh water, there was settlement. And with settlement, came cemeteries.

Arriaza has spent his career studying the Chinchorro and their mummies. He identifies the Camarones region as particularly special, because that’s where the Chinchorro first started intentionally transforming a corpse into art.

Read more: The Migration of Ancient Indigenous People in South America is a Complex Tale

Why Did the Chinchorro Mummify Their Dead?

The urge to preserve the dead prevails in many cultures. The Chinchorro mummies were unique not just because they sprang from a less hierarchical or complex society, but they also preserved children and babies.

What Did the Chinchorro Mummies Die Of?

Arriaza posits arsenic poisoning as the reason why. The rivers snaking through the Atacama Desert ran rich with naturally occurring arsenic, due to volcanic pollution. The Camarones had the highest levels of all at 1,000 micrograms per liter (a hundred times the safe consumption level).

Ingesting too much arsenic leads to a myriad of health problems: organ damage, skin hyperpigmentation, and cancers. It also causes reproductive problems, inducing miscarriages, stillbirths, and higher infant mortality. Likewise, the oldest mummies uncovered in the Camarones area are of infants, dating to around 5000 B.C.

“These people were probably the early settlers of the region, so they were not exposed to arsenic before,” Arriaza says. “Because of grief, they started to paint and ornament their babies.”

About 600 years later, the practice shifted farther north to Africa. As the preservation grew refined, the Chinchorro began preserving adults, too. It was care given to all members of society, no matter their age or status.

Read More: Medical Practitioners Once Used Egyptian Mummy Remains to Treat Ailments

How Did the Chinchorro Make Mummies?

Transforming corpses into mummies was a labor of love, requiring extensive anatomical knowledge and skill.

Essentially, the Chinchorro deconstructed the body of flesh and skin, before reassembling the remaining bones into an effigy. They stuffed and reinforced the body with materials like reeds, clay, and feathers, and patched the mummies back together with skins. Clay masks, modeled with open eyes and parted mouths, preserved life in their faces.

The final step of mummification was painting the body. In one style, the Chinchorro covered the entire body in a deep black made from manganese oxide. In another, they produced vibrant, colorful memories of the dead by decorating the body in red ochre paste, leaving the face painted black.

What Did Chinchorros Do With Their Mummies?

These elaborate funerary rituals, and even the process of collecting the necessary minerals for painting, was evidence of the Chinchorro’s social organization. Moreover, they showed that mummification was a communal effort to assuage pain, in the face of devastating loss.

“When someone dies, society falls apart,” Arriaza says. “When you have a body that is painted and decorated, somehow, you may rejoice to see somebody that is beautifully painted and decorated in their last trip for the hereafter.”

Read More: This 2,300-Year-Old Mummy Has a Heart (and Tongue) of Gold

How are Scientists Saving Chinchorro Mummies?

Because the mummies are now decaying, experts are trying to understand how to preserve them. Dehumidifiers can help preserve mummies in museum exhibits, since 45 to 50 percent humidity is the optimal environment according to the study authors. Ideally, mummies would also each have their own climate-controlled cubicles in museums, both to protect the individual and to keep out invasive environmental microbes.

For mummies still resting in shallow sandy cemeteries, more research is needed to determine how to best protect them. Removing the bodies immediately puts them at risk of deterioration, and available space in existing museums is limited.

Where Are the Chinchorro Mummies Now?

Fortunately, a new museum is working to house even more fragile mummies. In the meantime, archaeologists are flagging mummies exposed to elements and reburying them in the soil.

Finally, raising awareness of Chinchorro culture is also key. In 2021, United Nations Educational Scientific and Cultural Organization (UNESCO) added Chinchorro mummies and settlements to its world heritage list. While maintaining those sites is an ongoing process, Arriaza is hopeful the UNESCO name will make Chinchorro culture much more visible.

“We work from a small place in northern Chile, and sometimes you don’t have all the resources to do that,” he says, “but we do it with a lot of passion.”

Read More: Scientists Study the Secrets of 2,500-Year-Old Mummified Animals