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A Mystery in the Desert

10 September 2009 (All day)
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Maria Antonietta Costa

Medical mystery. What ate away the faces of these two ancient Chilean skulls?

In the early 1970s, archaeologists unearthed an unusual find in an ancient Chilean cemetery: the skulls of four women whose faces had seemingly been eaten away. None of the other 500-to-1000-year-old bones in the cemetery displayed the same disfigurement. Now, thanks to the region's arid climate, which helped mummify some of the women's facial tissue and brains, scientists think they have figured out what happened.

The cemetery--known as Coyo Oriente--lies near the city of San Pedro de Atacama, in the driest desert on Earth, the Atacama. Archaeologists say the land belonged to the ancient Atacameños, farmers and llama breeders, who wrapped their dead in finely woven cloth before placing them in their sandy graves.

A total of 255 skulls, including the four disfigured ones, were unearthed from the cemetery, and all contained bits of mummified brains and tissue. Maria Antonietta Costa, a physical anthropologist at the Catholic University of the North, San Pedro de Atacama, has painstakingly removed these small pieces over the past 30 years in an effort to figure out what happened to all of the people, including the four women.

At the 1998 Third World Congress on Mummy Studies in Arica, Chile, Costa asked paleoneurobiologist Otto Appenzeller of the New Mexico Health Enhancement and Marathon Clinics Research Foundation in Albuquerque his opinion of the four skulls. "It could have been leprosy, cancer, even tuberculosis," Appenzeller recalls telling her. In hopes of solving the mystery, the duo sent samples to Carney Matheson at the Paleo-DNA Research Laboratory at Lakehead University in Thunder Bay, Ontario. He retrieved and amplified sufficient DNA to discover genes belonging to the parasitic protozoan Leishmania, which causes leishmaniasis. There are more than 30 species of this parasite, which is transmitted by various species of sand flies and attacks visceral organs, mucous membranes, or the skin. The scientists suspect that the women suffered from the mucocutaneous form, which causes chronic ulcers and lesions around the nose, eyes, and mouth if untreated.

Although leishmaniasis is endemic throughout much of South America, this is the first time it has been found in a South American mummy, the team reports online today in PLoS ONE. A previous x-ray study of skeletal remains from the cemetery had revealed lesions reminiscent of leishmaniasis in 2% of the bones.

"Leishmaniasis didn't occur to me" when he first looked at the skulls, says Appenzeller, because the disease isn't found in San Pedro de Atacama today. And it was unlikely to have been there a millennium ago, he says, because the region's dry weather prevents the parasite from completing its life cycle.

So how did the four women contract the disease? "We think that they were immigrants, Yungas," says Appenzeller--people who lived 400 kilometers away in the tropical lowlands on the eastern slope of the Andes, where leishmaniasis is endemic. The high-altitude Atacameños prized the hallucinogenic drugs of the lowland Yungas, leading to an extensive trading network; the two peoples likely intermarried as well. Most probably, the scientists say, the four women contracted the disease in their youth in the lowlands and married Atacameños before the facial lesions, which can take up to 20 years to develop, were apparent.

If the desert climate had not stopped the parasite, it could easily have become endemic in the Atacama, because "everything else it needs for its life cycle--sand, rodents, and dogs--is there," says Appenzeller. "Only the climate halted it." And in that bit of geographical good fortune, the researchers see a warning. "With today's climate change, and the movement of people, leishmaniasis is spreading," says Appenzeller, who notes that more than 600 U.S. service members stationed in Iraq have come down with the Old World form of the disease. The World Health Organization reports that leishmaniasis kills some 60,000 people a year and is the second largest parasite killer after malaria.

"It's a great study and should bring attention to this pathogen, which needs to be tracked and controlled," says Raffaella Bianucci, a physical anthropologist at the University of Turin, Italy. "Maybe because of climate change or migration, the disease is now in northern France and Germany, places you would never expect to find it in the past."

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