Ancient Plague Killed Siberian Hunter-Gatherers 5,500 Years
Ancient DNA from Siberian burials shows plague was lethal in small, mobile groups long before medieval epidemics, with strains carrying a potent
Plague killed hunter-gatherers in Siberia 5,500 years ago, according to a new study published in Nature. The research, led by an international team, identifies lethal Yersinia pestis strains in human remains from the Lake Baikal region.
An international team studied ancient DNA from 46 individuals buried at four hunter-gatherer sites near Lake Baikal. They found genetic evidence of Yersinia pestis, the plague bacterium, in 18 people. This detection rate of nearly 40 percent exceeds that of some medieval plague cemeteries.
Ancient DNA Reveals Family Tragedies
The analysis combined genetics, archaeology, and radiocarbon dating. Senior author Eske Willerslev, a professor at the University of Copenhagen and the University of Cambridge, stated that the findings demonstrate these ancient strains were "already highly lethal." Radiocarbon dates show many deaths occurred close together. Siblings died together. Graves contain parents and children who likely perished in the same outbreak.
Lead author Ruairidh Macleod, a research fellow at the University of Oxford, explained the comprehensive approach. Based on the plague DNA, the genetic relationships between the victims, the archaeological analysis and the radiocarbon dating, we've built a really clear, complete picture of what happened during these outbreaks, Macleod said.
A Puzzle of Young Victims Solved
Archaeologists had long been puzzled by the high number of children and young teenagers buried at the two largest cemeteries over a short period. Andrzej Weber, an archaeologist at the University of Alberta and Principal Investigator of the Baikal Archaeology Project, called the discovery extraordinary. "The unusually high number of children and the short timespan was a real puzzle that we've been trying to solve since the 1990s." Weber said.
The findings challenge previous assumptions. Earlier research indicated ancient plague strains lacked genetic adaptations for efficient flea-borne transmission. Scientists therefore thought early versions caused only mild disease. The new evidence suggests these prehistoric outbreaks were severe.
A Genetic Factor for Lethality
The ancient bacterial genomes carried a distinctive superantigen, a toxin-producing genetic factor absent in historic plague strains. Senior author Martin Sikora, an associate professor at the University of Copenhagen, explained its significance. This finding changes our understanding of the earliest plague outbreaks: Even before the bacterium evolved efficient flea-borne transmission, these ancient strains appear to have carried a potent combination of virulence factors that could make infection highly lethal, Sikora said.
Superantigens can provoke extreme immune reactions, leading to severe inflammation and dangerous infections. This genetic factor may explain the high lethality, particularly among the young.
Origins in Rodent Hosts
The study supports the theory that plague emerged in Central or North-East Asia. Archaeological evidence shows the Lake Baikal hunter-gatherers had close contact with marmots. These large burrowing rodents are known plague carriers today. Researchers suspect direct transmission from infected marmots to humans triggered these prehistoric outbreaks.
Plague was therefore a deadly threat to small, mobile communities millennia before the crowded cities and flea-driven epidemics of the medieval period. The disease's history is far older and more complex than previously believed.
