Ancient Siberian graves show plague was deadly 5,500 years ago

Ancient plague was not a slow, harmless prelude to the Black Death. DNA recovered from teeth in four hunter-gatherer cemeteries near Lake Baikal in East Siberia shows Yersinia pestis was already tearing through small mobile communities about 5,500 years ago, long before agriculture and cities reshaped human life.

Researchers analyzed human remains from 46 people and found plague DNA in 18 of them, nearly 40 percent. The largest cemetery, Ust'-Ida I, had a 38.7 percent detection rate. The outbreaks date to about 5,600 to 5,400 years ago, and the pattern suggests two early waves of infection spread across graves on the banks of the Angara River.

The genetic evidence points to something close to household transmission. By reconstructing kinship pedigrees, the team concluded that small familial groups were affected and that the first outbreak unfolded within a single generation. That matters because it suggests the disease was not merely present in the landscape, but moving through people fast enough to kill family clusters before the dead had time to be forgotten.

The cemetery record also tells a grim demographic story. Children and young teenagers were disproportionately represented among the dead, hinting that the infection hit the most vulnerable hardest. Ruairidh Macleod, now a research fellow at the University of Oxford, said the team built a “really clear, complete picture” of the outbreaks. Eske Willerslev of the University of Copenhagen and the University of Cambridge said the findings show these ancient strains were already “highly lethal.”

That conclusion sharply revises an older view of plague evolution. A 2021 study identified the oldest known Y. pestis genome in a 5,000-year-old hunter-gatherer from Riņņukalns in present-day Latvia, and that strain was thought to be less contagious and less deadly than medieval plague because it lacked the flea-transmission gene. The new Siberian genomes suggest an earlier branch of the bacterium was capable of fatal outbreaks even without the later urban machinery of mass spread.

The Black Death, which began in 1347 and is estimated to have killed as much as half of Europe’s population, no longer stands as the point when plague first became devastating. Ancient DNA is now showing a harsher origin story: a lethal pathogen moving through scattered hunter-gatherer communities thousands of years before Europe’s great pandemic, and doing so with deadly efficiency.