Bones from 4,000-year-old human skeletons discovered in Chile contain evidence of a rare form of Hansen’s disease, also known as leprosy, ancient DNA reveals.
Whereas the more common form of leprosy known today is caused by a bacterium called Mycobacterium leprae, these skeletons had evidence of a different, rarer form of the disease caused by the bacterium Mycobacterium lepromatosis. The findings, published June 30 in the journal Nature Ecology and Evolution, suggest that the two leprosy-causing bacteria evolved separately, on opposite sides of the globe, for thousands of years.
To make the discovery, the researchers reconstructed the genome of the M. lepromatosis from the remains of two adult males found at the neighboring archaeological sites of Cerrito and La Herradura in northern Chile.
“This reshapes our understanding of the disease’s history and raises new questions about how it arrived and spread in the Americas,” said Charlotte Avanzi, who studies the spread and genomics of leprosy at Colorado State University and was not involved with this study.
The origins of leprosy
Leprosy is a chronic infectious disease with a host of painful symptoms, including skin lesions and limb numbness. It can lead to specific, observable changes in bone, and these characteristic transformations have been found in skeletons in Europe, Asia and Oceania from as far back as 5,000 years ago, according to a statement from the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany.
The disease is usually caused by M. leprae, which has been widely studied. Archaeological analysis of bones from Europe point to Eurasia as the origin of the bacteria, likely emerging about 6,000 years ago during the Neolithic transition from foraging to farming.
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Until now, there was no documented evidence of these changes in bone from the Americas before the colonial period, which suggested that leprosy was introduced to the region during that time. This research is complicated by the onslaught of pathogens that came to the Americas during that era and the difficulty of determining a diagnosis from ancient DNA, according to the statement.
“Ancient DNA has become a great tool that allows us to dig deeper into diseases that have had a long history in the Americas,” Kirsten Bos, a molecular…
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