Plague was already killing humans 5,500 years ago: ancient DNA rewrites the history of the disease
The history of plague was long anchored to the Black Death of 14th-century Europe. Scholars later added the 6th-century Plague of Justinian. A new study summarised in Science Daily now pushes the disease much further back — to hunter-gatherer communities of the Neolithic, thousands of years before the spread of agriculture.
The paper presents ancient DNA from two individuals exhumed in south-western Siberia. Radiocarbon dating places the burials at roughly 3,500 BCE, or 5,500 years before the present. Genomic analysis confirms a form of Yersinia pestis carrying all the key virulence genes.
This recalibrates the standard story of plague evolution. The dominant view positioned plague as a disease of settled farming societies, where the density of the rodent-flea-human triangle made transmission viable. That framework placed the first human strains in the early Bronze Age.
The new finding does not dismantle that framework but expands it materially. The two individuals belonged to small-scale hunter-gatherer communities. The cluster of nearby graves may point to epidemic transmission; the team's next step is to sample additional burials at the same site.
Two genetic features stand out. First, the strain still lacks the ymt gene that enables flea-borne transmission. Bacterial spread is therefore thought to have occurred through respiratory droplets or direct contact — not through the fleas of the medieval picture.
Second, the virulence-gene clusters are broadly similar to medieval variants. That suggests the bacterium did not have a mysterious Siberian past, but circulated across large parts of the world long before the 14th-century pandemic.
The finding ties into a wider debate about the origin of epidemic diseases. Settled farming, close contact with domestic animals and population density have been the classical preconditions for new pathogens to jump to humans. Plague complicates that frame: animal-to-human transmission could occur in looser population structures.
One author told Science Daily that "hunter-gatherers were more mobile and more interconnected than we often assume; that mobility also suited pathogen transmission." Siberia's wide grasslands are connected by seasonal herd routes.
The study has present-day public-health relevance. Plague today is detected at around 1,000-2,000 cases per year in Madagascar, the western United States and rural China; with treatment, the mortality rate falls below 10%, but rapid diagnosis remains critical.
Ancient DNA has rewritten disease history several times in the past decade. The genomes of tuberculosis, smallpox and syphilis have been similarly pushed back in time. The new 5,500-year-old "first human evidence" bar for Yersinia pestis once again deepens the place of epidemic disease in the human story.
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