The plague already struck hunter-gatherers of Lake Baikal 5,500 years ago

5,500 years ago, deadly plague epidemics were already devastating communities of hunter-gatherers living near Lake Baikal in Siberia. These findings challenge the idea that the plague only spread with the rise of agriculture and the sedentarization of populations. The research reveals that these early strains of the responsible bacterium, Yersinia pestis, were indeed lethal, even though they did not yet possess all the genes enabling transmission by fleas, a characteristic of bubonic plague.

The evidence comes from four cemeteries where nearly 40% of the analyzed individuals showed traces of the infection. Genetic analyses show that the epidemics occurred in two distinct waves, separated by several centuries. The victims, often children aged 8 to 11, suggest acute mortality, particularly high among the youngest. The researchers reconstructed the kinship ties between the deceased and found that small family groups were affected, confirming human-to-human transmission.

Unlike later strains, these ancient bacteria lacked the genes necessary to survive in the digestive system of fleas, a key element for the spread of bubonic plague. Yet, their danger was real. Scientists identified functional differences, such as the presence of a gene encoding a superantigen toxin, similar to the one found today in Yersinia pseudotuberculosis, a closely related bacterium. This toxin, called YPM, stimulates an excessive immune response, which can cause severe inflammatory complications, particularly in children.

Marmots, which are still natural reservoirs of the plague in this region today, may have played a central role in transmission. Hunter-gatherers, by handling these animals for their meat or fur, could have contracted the disease orally or through respiration. Collective burials and the proximity of the deceased suggest simultaneous deaths, consistent with rapid spread within groups.

These findings show that the plague could have spread long before the Neolithic era, without requiring population densification or major changes in lifestyle. The epidemics around Lake Baikal demonstrate that zoonoses—diseases transmitted by animals—have always posed a major threat to humanity, even in mobile and low-density societies.

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Source de l’étude

DOI : https://doi.org/10.1038/s41586-026-10540-5

Titre : Lethal plague outbreaks in Lake Baikal hunter-gatherers 5,500 years ago

Revue : Nature

Éditeur : Springer Science and Business Media LLC

Auteurs : Ruairidh Macleod; Frederik V. Seersholm; Bianca De Sanctis; Angela Lieverse; Adrian Timpson; Rick Schulting; Jesper T. Stenderup; Charleen Gaunitz; Lasse Vinner; Olga Ivanovna Goriunova; Vladimir Ivanovich Bazaliiskii; Sergei V. Vasilyev; Erin Jessup; Yucheng Wang; Christopher Bronk Ramsey; Mark G. Thomas; Russell Corbett-Detig; Astrid K. N. Iversen; Andrzej W. Weber; Martin Sikora; Eske Willerslev