About 5,500 years ago, groups of hunters - food collectors lived in the region of Lake Baikali in Siberia and were maintained by its rich resources, mainly prey such as elks, deer, fish, seals and marmots, a species of rodents. These people were the victims of the oldest known plague epidemic that particularly affected children and adolescents.
Researchers say that ancient DNA obtained from bodies buried in four locations in this area revealed the presence of the oldest known strains of Yersinia pestis (Wors of plague), the plague bacterium. These prehistoric deaths foretold the enormous suffering that this rosary would cause mankind over the centuries.
The epidemic was particularly deadly for young people, judging by burial sites, and researchers attribute this event to genetic characteristics of the bacterium strain no longer present in the present form of the pathogen. They also stated that the discovery strengthens the evidence that the marmots were the original species-host of the bacterium and that the plague appeared in central or northeast Asia before spreading throughout Eurasia.
Oldest known plague outbreak Occurred in Siberia 5,500 years ago, study finds
On Wednesday, researchers published findings in Nature revealing the oldest known plague outbreaks, dating back about 5,500 years old hunter-gatherers built near Lake Baikal, Siberia.
This discovery... pic.twitter. com/ezwM68JRPH— Jonny (@TheeOutpost) June 17, 2026
"The findings radically change the way we think about the origin and impact of one of humanity's most defining pathogens," said Danish evolutionary geneticist Eske Villerslev, a professor at the Universities of Copenhagen and Cambridge and a key author of the study published today in Nature magazine.
The next oldest known case of plague epidemic dates back about 5,300-5,000 years in Latvia, about 5,000 km away.
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Vladimiri Bazaliiskii/Handout via REUTERS
"Only by developing methods to study ancient DNA have we discovered that it has existed for a long time than we know from historical records. It is a zoonose, a pathogen that mainly affects rodents rather than humans, but which has repeatedly switched to humans with devastating results," said the evolutionary geneticist of the University of Oxford and of the main authors of the study, Rorid MacLeod.
Two epidemics exterminated a large proportion of Europe’s population — the Justinian Plague in the 6th century and Black Death in the 14th century, when the plague spread to humans through stings from infected fleas carried by rats.
For a long time scientists found that significant outbreak of plague only occurred after humanity began agriculture and created settlements with high population density. There were also thoughts that early strains might not be so deadly. The discovery that the plague killed prehistoric hunter-gatherers wandering in a remote forested landscape in groups that numbered a few dozen people each, refuted these perceptions.
At Lake Baikal, the Gersinia of the plague was detected in 18 of the 46 remains examined, a higher percentage than in some medieval group graves of plague victims. MacLeod stated that identifying evidence of a large-scale deadly plague outbreak among these hunter-gatherers surprised him.
‘Transitional stage’
Researchers recovered many Yersinia pestis genomes that had been preserved in the teeth of the buried plague victims. These strains were very close to the ancestral root of a bacterium that had diverged from its evolutionary predecessor perhaps only two centuries earlier.
"The pathogen appears to represent a transitional stage in the evolution of plague. He was already capable of causing serious disease, but did not have the gene necessary for effective transmission through fleas," said Willersev. It also did not cause painful swelling in the groin, as was the case in the following epidemics. However, unlike later strains, it could cause a serious, inflammatory complication, in which children are vulnerable in particular. Many of the victims found in Siberia were children and some of them brothers among themselves.
Lethal plague outbreaks in Lake Baikal hunter-gatherers 5,500 years ago https://t.co/EWiWanKtw— Digital Brain (@digitalbrain01) June 17, 2026
"This vulnerability is higher for children between the ages of 8 and 12, and it is clearly a completely different pattern of mortality than we see at other hunting-gathering sites in Baikal, where no plague is detected," MacLeod said.
"In conjunction with the presence of other genes that make plague infections serious, it is clear that these prehistoric plague strains were equally capable of being fatal, although in a different way," MacLeod completed.
These hunter-gatherers came in close contact with the marmots, and researchers reported that these rodents seem to have fed the outbreak of the disease. At other locations, medallions made from the front teeth of marmotas had been included in burials. Marmotes were also a source of food.
"Some people may have come into contact with an infected marmot, possibly catching it or eating meat that had not been well cooked," MacLeod said.
Researchers believe that, after the pathogen was switched from molars to humans, it spread through human transmission, for example by coughing.
"This epidemic destroyed the hunting-gathering communities of that time. Clearly, at least a few people were left alive to bury the dead, and apparently they knew who was who, as young brothers were buried together in common graves," he explained.