The oldest known traces of the plague, dating back 5,500 years, have been identified in hunter-gatherer burials near Lake Baikal in Siberia, according to a study published in Nature on June 17, 2023. Researchers found evidence of Yersinia pestis infections in 18 individuals out of 46 analyzed, challenging prior assumptions that plague outbreaks were linked to agricultural societies.
What does the discovery reveal about ancient plague outbreaks?
The study, led by archaeologist Ruairidh Macleod of the University of Oxford, analyzed DNA from remains at four burial sites near Lake Baikal. The team identified Yersinia pestis in 18 individuals, many of whom were buried in mass graves with signs of rapid interment. This suggests a fatal outbreak occurred among hunter-gatherer communities, contradicting the hypothesis that plague emerged only after the rise of farming and dense settlements.
“We weren’t expecting this result at all,” Macleod said. “There was an expectation that these big outbreaks don’t really happen among prehistoric hunter-gatherers [but only] with people living in high-density settlements.”
How was the plague transmitted in prehistoric times?
The researchers propose that marmots, large burrowing rodents common in the region, were the primary reservoir for Yersinia pestis. While other animals like birds could have played a role, marmots are known to carry the bacterium and interact closely with human populations. The Siberian strain of the plague was found to have genes linked to virulence, making it more deadly than earlier forms.
This discovery predates the previously oldest plague evidence—found in a 5,000-year-old grave in Latvia and a Neolithic mass grave in Sweden—by several centuries. The Lake Baikal strain also represents the oldest known divergence of Yersinia pestis from a less lethal ancestor, occurring at least 5,700 years ago in Central Asia.
Why does this challenge existing theories about plague origins?
Historically, researchers believed plague outbreaks were tied to the rise of agriculture, as farming communities created conditions favorable to rats and fleas. However, the Siberian findings indicate that hunter-gatherers faced plague risks long before settled life. Nicolás Rascovan, a molecular biologist at Institut Pasteur in Paris, called the discovery “clear evidence of an outbreak in prehistoric times that argues against agricultural lifestyles as a major driver of plague emergence.”
Rascovan noted that the study highlights gaps in understanding plague evolution. “There are still several thousands of years of Y. pestis evolution and spread that have been overlooked,” he said. “I believe there are still many surprises to come in the history of the plague.”
What implications does this have for modern plague research?
The discovery underscores the complexity of plague transmission and its deep historical roots. By identifying the Siberian strain’s genetic makeup, researchers can better trace how the bacterium adapted over time. This may inform efforts to predict future outbreaks and understand the interplay between human activity and zoonotic diseases.
Experts emphasize that while the study provides critical insights, further research is needed to confirm the exact transmission pathways and ecological factors that enabled the plague to spread among hunter-gatherers. The findings also raise questions about how other ancient pathogens may have shaped human history.
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