Scientists have discovered the oldest known evidence of the plague, pushing its documented history back by some 200 years to approximately 5,500 years ago. The groundbreaking finding offers a crucial new perspective on the origins of a disease that has profoundly shaped human civilisation, including the devastating Black Death of the 14th century.The plague, though now rare and treatable with antibiotics, has afflicted humanity for millennia. Researchers, led by evolutionary geneticist Eske Willerslev from the University of Copenhagen, examined remains from four cemeteries near Siberia's Lake Baikal. Willerslev stated: "To understand our own history, we believe that understanding the history of plague is extremely important."Their analysis of teeth from 18 ancient hunter-gatherers revealed remnants of plague-causing bacteria DNA. Carbon dating indicated two distinct outbreaks, with the earliest cases emerging around 5,500 years ago. The team suggests this prehistoric plague developed in stages, infecting several small families. It likely spread from marmots — large native rodents — when people ate their raw organs or touched infected hides during butchery. The disease also travelled between people through coughing and sneezing, the authors said.This 2019 image from Angela Lieverse shows the skull of an adult woman who was infected with the plague and was buried in Siberia (Angela Lieverse)Many victims were young children, aged between eight and eleven, possibly due to weaker immune systems. The study, published in the journal Nature, highlighted poignant burial arrangements, including three young girls laid side by side, two believed to be cousins, and an aunt and nephew interred together, though her niece was found in a different shared grave. Ruairidh Macleod, an ancient DNA expert at the University of Oxford and study co-author, noted the profound human connection: "People were around to bury the dead who knew who these people were when they were alive. And that’s a really human element to all of the scientific work."Geneticist Aida Andrades Valtueña, from the Max Planck Institute for Evolutionary Anthropology, who was not involved in the study, observed that the presence of multiple victims suggests the prehistoric plague was capable of causing both individual cases and wider outbreaks. Researchers found that this ancient strain evolved long before the bubonic plague, which was responsible for the Black Death that struck medieval Europe. Crucially, there is evidence that these earlier plagues were just as deadly, decimating not only crowded cities but also small, nomadic hunter-gatherer groups. Understanding this early evolution, Andrades Valtueña said, can help us "understand the steps that the bacterium took to become the deadly pathogen we know today, and that can provide clues on how pathogens may emerge in the future."