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Ancient Plague Outbreaks Hit Lake Baikal Hunter-Gatherers 5,500 Years Ago
A new ancient DNA study has revealed that lethal plague outbreaks affected hunter-gatherer communities near Lake Baikal in southeast Siberia around 5,500 years ago. The research identifies early strains of Yersinia pestis, the bacterium that causes plague, in human remains from four prehistoric cemeteries along the Angara River.
The findings are important because early plague strains lacked some of the genetic features needed for classic flea-borne bubonic plague. For this reason, researchers have debated whether these early forms of plague were highly dangerous or caused milder infections. The new evidence from Lake Baikal suggests that at least some early plague outbreaks were lethal.
Researchers analysed ancient human and pathogen DNA from 46 Late Neolithic hunter-gatherer individuals. Plague DNA was detected in 18 of them, giving an unusually high detection rate of 39%. The cases came from four cemeteries: Ust’-Ida I, Shumilikha, Bratskii Kamen, and Serovo.
The outbreaks appear to have occurred in two phases. The first began around 5,500 years ago, while a later phase followed several centuries afterward. Genetic analysis showed that the Lake Baikal plague strains were very early branches of Y. pestis, older and more basal than many previously known prehistoric plague genomes.
The study also reconstructed biological relationships between the buried individuals. At Ust’-Ida I and Bratskii Kamen, several plague-positive individuals were close relatives, and some were buried together in shared graves. This pattern suggests that small family groups were affected and that human-to-human transmission may have occurred.
Children seem to have been especially vulnerable. The mortality profiles at Ust’-Ida I and Bratskii Kamen show an unusually high number of deaths among children, especially around 8 to 11 years old. At Bratskii Kamen, three young girls buried together all tested positive for plague DNA, indicating a sudden and severe event within a family group.
The researchers suggest that the disease may originally have spilled over from wild animals, especially marmots, which remain important plague reservoirs in parts of Inner Asia today. However, the burial and kinship evidence points to transmission among people after the initial spillover.
Because these communities were mobile hunter-gatherers, the findings challenge the idea that plague epidemics required dense farming settlements or major lifestyle changes linked to the Neolithic agricultural transition. Instead, the evidence shows that serious zoonotic outbreaks could affect small prehistoric forager groups as well.
Overall, the Lake Baikal evidence pushes the history of lethal plague outbreaks further back in time and broadens the setting in which early plague is known to have affected humans. It shows that plague was already a dangerous disease among hunter-gatherers long before the later, better-known bubonic plague pandemics.
Published on: 18-06-2026
Edited by: Abdulmnam Samakie
Source: Nature
