Leprosy was active and present in the Americas before the arrival of the Europeans in 1492. A recent study published in Science (Pre-European contact leprosy in the Americas and its current persistence) reported that a second strain of a pathogen that causes the disease, which has been named Mycobacterium lepromatosis, was found in ancient remains of Pre-Hispanic natives.
On a global scale, the majority of leprosy cases are caused by another related bacterium, Mycobacterium leprae. So the "American" variety is quite unique, it was, until the arrival of Europeans, exclusive to the American continent. Both strains are related, and have a common ancestor (more on this below).
This paper found the second strain in the remains of a human being from the area along the Alaska-Canadian border and remains from Argentina. Modern cases of this strain have almost identical genomes to the ancient ones indicating that it mutates very slowly. The authors estimate that the M. lepromatosis has been evolving isolated in America for the past 10,000 years. But they can't assure if it originated in America, or if it was brought by some animal or human agent.
Both M. leprae and M. lepromatosis shared a common ancestor 720,000 years ago. This means that the American and Rest-of-the-World strains split at the time Denisovans and Neanderthals split from the branch that led to Modern Humans. As the American strain was not found elsewhere until European contact dispersed it (it also introduced the global variant into America)... Could this imply that the Denisovan-Neanderthal people reached America with this leprosy strain where they remained isolated from the other global strain?
There are four clades of this American leprosy, all in the Americas, but a fifth one has been detected in the UK: "infecting red squirrels in the British Isles raises the possibility that this lineage originated in the Americas well before any known historical or zoonotic connections between the Americas and other continents, given its estimated divergence time of 3,200 BP."
This suggests somehow that the bacterium moved across the Atlantic from America to Britain. The authors try to find an explanation for this, but it isn't convincing. Perhaps some Mediterranean vessels in the tin trade with Britain crossed the Atlantic and brought back squirrels that somehow infected their British relatives? A stray Norse ship? Phoenicians? A mystery.
Patagonian Monsters - Cryptozoology, Myths & legends in Patagonia Copyright 2009-2025 by Austin Whittall ©
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