Ancient teeth reveal plague was killing hunter-gatherers long before cities existed

Most people connect plague with rats, dense cities, and the devastation of the Middle Ages. 

According to ScienceDaily, new research raises a darker possibility: the disease may have hit hunter-gatherer communities well before urban life began.

What happened?

A study in Nature reports that plague was killing people near Lake Baikal in East Siberia roughly 5,500 years ago.

Researchers from several countries studied DNA preserved in teeth from human remains buried at four hunter-gatherer cemeteries. That analysis revealed previously unknown early strains of Yersinia pestis, the bacterium responsible for plague.

The bacterium was detected in 18 of the 46 people examined, so evidence of infection appeared in nearly 40% of the remains.

Senior author Eske Willerslev, a professor at the University of Copenhagen and the University of Cambridge, said, "Whether the earliest forms of plague were mild or virulent has been a matter of debate, but our findings demonstrate that these ancient strains were already highly lethal."

To piece together the outbreaks, the team paired the DNA results with radiocarbon dating and archaeological evidence.

In the two biggest cemeteries, they saw an unusually large share of children and young teenagers among the dead, as well as burials suggesting that siblings or parents and children died at about the same time.

Why does it matter?

The findings push back against the long-held view that the earliest plague strains lacked the traits required for the later flea-and-rodent route of transmission and, for that reason, were unlikely to drive large, fatal outbreaks.

Instead, the evidence indicates that these older strains could still be highly dangerous.

The researchers also found a distinct superantigen, a toxin-producing genetic factor absent from later historic plague strains.

Senior author Martin Sikora, associate professor at the University of Copenhagen, said, "This finding changes our understanding of the earliest plague outbreaks: Even before the bacterium evolved efficient flea-borne transmission, these ancient strains appear to have carried a potent combination of virulence factors that could make infection highly lethal."

Plague has not disappeared and still shows up in limited areas today, usually associated with wild rodents. Even so, modern surveillance, sanitation, and antibiotics make it far easier to manage than it was in the past.

Research like this helps scientists trace how pathogens emerge, evolve, and pass between animals and humans, which can strengthen disease monitoring and response.

What are people saying?

Ruairidh Macleod, the lead author and now a research fellow at the University of Oxford, said the evidence created "a really clear, complete picture of what happened during these outbreaks."

Andrzej Weber, an archaeologist at the University of Alberta and principal investigator of the Baikal Archaeology Project, said, "The unusually high number of children and the short timespan was a real puzzle that we've been trying to solve since the 1990s. Finding out that plague was the cause is extraordinary, but it makes so much sense."

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