When most people think of leprosy, they picture history books or ancient tales. The disease is rarely linked to early populations in the Americas. However, new research challenges that assumption in a surprising way. A recent study published in Nature Communications sheds new light.
Researchers studied two ancient skeletons from northern Chile. They found DNA from Mycobacterium lepromatosis, a rare leprosy-causing bacterium. This species causes Hansen’s disease, a lesser-known form of leprosy. The bones are about 4,000 years old.
This pushes back the known history of leprosy in the region. Until now, experts believed leprosy arrived with European colonizers. There was no confirmed bone evidence before the colonial era. These findings raise new questions about leprosy’s spread and origins.
Most known cases involve Mycobacterium leprae, which came from Eurasia. M. lepromatosis, by contrast, may have evolved in the Americas. The two bacteria likely emerged on opposite sides of the world. This discovery reshapes how scientists understand the disease’s global history.
How Did the Study Find Ancient Evidence of Leprosy in the Americas?
The study examined 41 ancient individuals from five Chilean sites. Researchers selected 35 teeth and 19 bones showing signs of infection. Each sample was processed to extract about 50 milligrams of DNA. The DNA was converted into single-stranded libraries for sequencing.
After screening for pathogens, two samples matched M. lepromatosis DNA. One came from a tibia, the other from a tooth. The samples were found at neighboring sites: La Herradura and El Cerrito. Radiocarbon dating placed them between 3,900 and 4,100 years old.
Both skeletons had lesions possibly linked to Hansen’s disease. However, these bone changes are not unique to leprosy. They cannot be used alone for diagnosis of the disease. Still, the damage raised suspicion of chronic infection.
The tibia specimen showed nasal rounding and jawbone recession. It also had rib pitting and abnormal growth in hand bones. The right tibia was thickened and bowed from healed inflammation. Clear lesions appeared on the right heel bone as well.
The other skeleton showed similar nasal rounding and tibial thickening. Fewer bones were preserved, but patterns echoed the first case. Researchers confirmed M. lepromatosis DNA using genome mapping techniques. The pathogen’s DNA was clearly present in both individuals.
DNA from the human remains confirmed Indigenous American ancestry. These findings provide rare, well-preserved evidence of ancient infection. They confirm the presence of leprosy in precolonial South America. This reshapes what we know about the disease’s early history.
How Does Ancient DNA Shed Light on Leprosy’s Genetic History?
Researchers compared ancient M. lepromatosis DNA to modern genomes. Some differences suggested possible gene loss in certain lineages. However, no clear pattern separated ancient from modern strains. Variations in gene presence likely reflect normal genetic diversity.
A broader analysis compared M. lepromatosis to M. leprae. M. leprae genomes show extensive gene loss over time. Despite being related, the two pathogens are genetically very different. M. lepromatosis is a distinct and deeply divergent leprosy-causing species.
Recognizing this distinction improves understanding of the disease’s evolution. It also helps scientists better identify infected samples in the future. Honoring the genetic differences between strains supports better diagnosis. This research strengthens efforts to track leprosy’s global spread and history.
Conclusion
These findings reveal that M. lepromatosis existed in the Americas millennia ago. The research challenges long-held beliefs about leprosy’s arrival and evolution. It also highlights the value of ancient DNA in disease discovery.
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Logan Hamilton is a health and wellness freelance writer for hire. He’s passionate about crafting crystal-clear, captivating, and credible content that elevates brands and establishes trust. When not writing, Logan can be found hiking, sticking his nose in bizarre books, or playing drums in a local rock band. Find him at loganjameshamilton.com.
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