Paris (AFP) - Seals and sea lions probably brought tuberculosis to the Americas centuries before Christopher Columbus first set foot there, scientists said Wednesday.
A new study challenges the theory that Europeans introduced TB to the New World, where it killed millions of indigenous Americans along with other foreign diseases like whooping cough, chicken pox and flu.
As many as 20 million people lived in the Americas before Europeans arrived, and up to 95 percent of them were wiped out by new diseases to which they had no immunity.
But the latest data revealed that TB "may have had a hand in American Indian deaths prior to the influx of European diseases", according to the US National Science Foundation (NSF), which co-funded the study.
An international expert team analysed DNA of bacteria from three 1,000-year-old human skeletons found in Peru, and found a type of TB closely related to strains that infect seals and sea lions today.
The finding provides a "plausible, if unexpected, route of entry into the New World", the study's authors wrote.
It means that seals and sea lions probably contracted the disease from a host animal from Africa, where the disease likely originated, and swam across the Atlantic to South America.
The mammals were probably eaten by coastal people who were themselves then infected and spread the bacteria to others, said the study, published in the journal Nature.
"The source of tuberculosis in the New World has long been a question for researchers," Elizabeth Tran, the NSF's biological anthropology programme director said in a statement.
"This paper provides strong evidence that marine mammals may have been the likely culprits."
The analysis also revealed that tuberculosis in the form we know it was much younger than originally thought, and probably only evolved in Africa about 6,000 years ago.