Oxford geneticist Ruairidh Macleod and his team sequenced DNA from teeth recovered at four cemeteries near Lake Baikal in southeastern Siberia. The analysis revealed Yersinia pestis bacteria in dozens of individuals, confirming the region experienced a lethal plague outbreak 5,500 years ago. This represents the earliest known human plague event, predating any Neolithic farmer cases, and reshapes our view of ancient disease dynamics.

Researchers used shotgun sequencing on dental roots, which capture bloodstream pathogens, to detect bacterial DNA without prior target selection. Eleven of thirty‑one tested individuals from the Ust‑Ida cemetery tested positive, a rate matching that of known medieval plague mass graves. The genome assembled from one sample sits near the base of the Y. pestis family tree, lacking later virulence genes.

The find overturns the long‑held belief that plague required dense settlements and domesticated rodents to spread. It shows mobile hunter‑gatherer groups could sustain deadly epidemics, likely through long‑distance kin networks. This ancient outbreak provides a genetic baseline for modern pathogen monitoring, highlighting how early bacterial evolution can inform current public‑health strategies and improve vaccine design against related bacterial threats.