Ancient DNA recovered from cemeteries in southeast Siberia has revealed previously unknown strains of plague that had a deadly impact on an unexpected group of people 5,500 years ago.The early plague strains, detailed in a new study published Wednesday in the journal Nature, may be the oldest known evidence of the disease in humans.Plague is caused by the bacterium Yersinia pestis and has led to some of the most devastating disease outbreaks in human history, including the infamous Black Death in the 14th century, which killed an estimated 25 million people over five years. Before the discovery of the newly identified strain, some of the earliest known strains of Yersinia pestis associated with bubonic plague had been dated to about 3,800 years ago.AdvertisementAdvertisementPreviously, older strains appeared to lack the genetic traits that enabled them to spread, leading scientists to think that early plagues were unlikely to trigger outbreaks. With sparse evidence of other lethal precursors of the disease, scientists questioned when and where the bacterium originated before it spread from early livestock such as sheep and infected fleas to humans.The newly discovered strain almost immediately seemed to add a twist to the story. Researchers came across it while they were trying to solve another puzzle in the remains of hunter-gatherers buried in cemeteries of the Lake Baikal region. Two of the largest cemeteries contained an unusually large number of children and young adolescents whose remains lacked any trauma or apparent cause of death.An analysis of ancient DNA within the remains revealed the unexpected presence of plague bacteria in 18 of 46 individuals from the small, mobile communities — as well as a genetic factor that might have increased the infection’s severity.The findings add to growing evidence that suggests where plague might have originated, experts say — and also challenge ideas about what enabled plague to spread.AdvertisementAdvertisement“Hunter-gatherers are constantly moving around the landscape,” said lead study author Ruairidh Macleod, a research fellow at the UK’s University of Oxford, during a news conference Tuesday to discuss the results.“The theory is that infectious disease can’t really take hold and devastate entire communities in this way. Typically, if somebody gets ill, they’ll move somewhere else. The fact that we’re finding this happening in an isolated group of prehistoric hunter-gatherers challenges that epidemiological theory.”An artist’s illustration shows Lake Baikal hunter-gatherers burying victims of plague 5,500 years ago. – Kelvin WilsonAn unexpected outbreakArchaeologists have excavated the four ancient cemeteries around Lake Baikal for decades. The region was rich in resources, including waters for fishing, an …
