September 3, 2013
Researchers Discover TB Originated In Humans 70,000 Years Ago
redOrbit Staff & Wire Reports - Your Universe Online
Despite previous research suggesting that tuberculosis originated in animals just 10,000 years ago, scientists have now traced the origin of the illness back to humans living in Africa at least 70,000 years ago.
According to BBC News science reporter Julie Gould, an international team of researchers “combined geographic and genetic data from 259 strains of TB to reconstruct its evolutionary history and compare it to the origins of humans in Africa.”
Sebastien Gagneux from the Swiss Tropical and Public Health Institute (Swiss TPH) and his colleagues used whole genome sequencing of those Mycobacterium tuberculosis strains, then compared them to the evolutionary tree of humans. They found a very close match between both of their evolutionary paths.
There were “striking similarities” between the ways that both humans and the TB bacteria developed, Gagneux said in a statement. He and his colleagues believe that their research shows a close relationship between the two, dating back tens of thousands of years and suggesting that they might have migrated out of Africa together.
“We see that the diversity of tuberculosis bacteria has increased markedly when human populations expanded,” the evolutionary biologist said. Gagneux added that human expansion occurring in the Neolithic Demographic Transition (NDT) period, combined with humans living together in larger groups, could have created the conditions necessary to spur on more efficient person-to-person transmission of the deadly infectious disease.
Previous research had indicated that human tuberculosis had only originated during the NDT period, which occurred approximately 10,000 years ago, Gould explained. During that transition phase, not only was the human population expanding, but agriculture was also becoming more prevalent, she added.
“We found that the most basal – the earliest – lineages of TB and humans originated in the same place, in Africa, 60,000 years earlier than what people previously thought,” Gagneux told BBC News. “What we have done is provide a strong hypothesis to reinforce the idea that TB originally started in humans, and migrated to animals during NDT.”
“The next step in this research would be to use genetic information to understand this activation and deactivation mechanism of TB,” added lead author Dr. Inaki Comas of the Centre for Public Health Research’s Genomics and Health Unit. His team’s research appears in the September 1 edition of the journal Nature Genetics.
Tuberculosis, which typically attacks the lungs but can also affect other parts of the body, kills 50 percent of those who contract the condition when it is left untreated, the researchers said. It is responsible for as many as two million deaths annually in developing nations, and multidrug-resistance is a growing threat in the fight against TB.