A longstanding archaeological mystery has loomed over discoveries at ancient burial sites in eastern Siberia: why were so many children and adolescents among the dead?
Now, according to a recent study in the journal Nature, DNA recovered from human remains found in burial sites at four cemeteries near Lake Baikal in eastern Siberia may finally reveal the answer.
Thousands of years ago, prior to the rise of ancient medieval cities—and their often-rat-infested streets—a disease famously associated with these rodents had already ravaged communities of prehistoric hunter-gatherers.
The research, based on reconstructions of ancient bacterial genomes preserved in the teeth of these ancient Siberians, revealed the presence of previously unknown strains of Yersinia pestis—the bacteria responsible for plague—providing fresh evidence that the lethal disease was already manifesting and killing human populations at least as far back as 5,500 years ago.
“Whether the earliest forms of plague were mild or virulent has been a matter of debate, but our findings demonstrate that these ancient strains were already highly lethal,” said senior author Eske Willerslev of the University of Copenhagen and the University of Cambridge.
New Evidence of an Ancient Siberian Plague
In their study, the team successfully located plague DNA in 18 out of 46 individuals they studied. Based on radiocarbon dating, many of the deaths were confirmed to have all happened within a short span of time, which is consistent with sudden deaths resulting from plague. Additionally, genetic evidence showed that several of these victims had been close relatives.
One key finding in the research involved the number of children and adolescents who were among the dead—a discovery mirroring earlier findings at prehistoric sites in the region, which had remained a longstanding archaeological mystery.
“The unusually high number of children and the short timespan was a real puzzle that we’ve been trying to solve since the 1990s,” said archaeologist Andrzej Weber of the University of Alberta. “Finding out that plague was the cause is extraordinary, but it makes so much sense.”
New Findings Challenge Old Assumptions
Based on the new findings, ancient strains of plague appear to have been more harmful than once thought. In the past, it was presumed that because these early strains lacked genetic adaptations that helped the bubonic plague spread so efficiently through fleas and rodents, they were relatively harmless.
The team’s research now reveals that these newly identified strains carried a specific toxin-producing genetic feature, known as a superantigen, which can trigger severe immune responses that potentially had devastating impacts on mortality rates in the ancient world.
Such deadly outbreaks may have had a far more significant impact on ancient human populations than previously realized, and during periods long before the rise of major urban centers and organized agriculture.
In terms of the origins of the disease, researchers believe that they may have finally traced it to Central or Northeast Asia, where infections may have spread from marmots, large rodents that are still recognized as plague carriers in modern times.
After years of uncertainty, the team’s research offers some of the best evidence to-date that one of the most devastating diseases in human history was already playing a role in shaping human history thousands of years earlier than once thought.
Martin Sikora, associate professor at the University of Copenhagen and the study’s senior author, says his team’s research “changes our understanding of the earliest plague outbreak,” and now confirms that such ancient strains “appear to have carried a potent combination of virulence factors that could make infection highly lethal.”
The team’s study, “Lethal plague outbreaks in Lake Baikal hunter-gatherers 5,500 years ago,” appeared in the journal Nature on June 17, 2026.
Micah Hanks is the Editor-in-Chief and Co-Founder of The Debrief. A longtime reporter on science, defense, and technology with a focus on space and astronomy, he can be reached at micah@thedebrief.org. Follow him on X @MicahHanks, and at micahhanks.com.