Hunter-gatherer cemeteries reveal an ancient plague’s earliest known victims | CNN

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. Previously, 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