A newly published study has uncovered the oldest known evidence of a deadly plague outbreak, revealing that humans were battling fatal infections nearly 5,500 years ago, long before the rise of cities and civilizations.

The research, published in Nature, analyzed ancient DNA from prehistoric hunter-gatherers buried near Siberia’s Lake Baikal in Russia. Scientists identified a previously unknown strain of Yersinia pestis, the bacterium that causes plague, challenging long-held assumptions about when and how the disease first became lethal.

TL;DR

• Scientists discovered the oldest known deadly plague strain in ancient human remains from Siberia.
• The findings date plague outbreaks to about 5,500 years ago, roughly 200 years earlier than previously known.
• Researchers identified a previously unknown strain of Yersinia pestis.
• The study suggests hunter-gatherer communities experienced devastating plague outbreaks before the emergence of cities.
• The findings were published in the journal Nature.

What did scientists discover?

Researchers from the University of Oxford analyzed DNA extracted from the teeth of 42 prehistoric hunter-gatherers buried at four archaeological sites near Lake Baikal in Siberia.

Alongside human DNA, they recovered genetic material from Yersinia pestis, the bacterium responsible for plague.

The analysis revealed a previously unknown strain that appears to have emerged around 5,700 years ago and caused widespread fatalities roughly 5,500 years ago.

According to the researchers, this is now the earliest confirmed evidence of a deadly plague outbreak in humans.

Why is this discovery important?

Until now, the oldest known strains of Yersinia pestis dated back about 5,300 years and were generally believed to have caused relatively mild disease.

The newly identified strain changes that understanding.

Researchers found evidence suggesting it was capable of causing severe illness and high mortality, particularly among children, despite lacking some genetic features previously thought necessary for highly virulent plague.

The discovery suggests plague became a significant human disease earlier than scientists had believed.

What happened during the outbreaks?

The study identified evidence of two separate plague outbreaks affecting communities in southeastern Siberia.

First outbreak

Around 5,500 years ago, several closely related individuals died at a settlement known as Ust’-Ida and were buried together in what researchers describe as mass graves.

Second outbreak

A few centuries later, another outbreak involving the same lineage of plague bacteria occurred approximately 37 kilometers away at Bratskii Kamen.

Researchers also found biological relatives among victims from both outbreaks, suggesting the same communities experienced repeated epidemics over several generations.

Why were children especially affected?

One of the study’s most striking findings was the high number of children among the victims.

Researchers found that children, particularly those between eight and 11 years old, appeared to suffer unusually high mortality rates.

The scientists believe the newly discovered strain carried a genetic feature not found in either modern or previously identified ancient plague strains, which may have contributed to its heightened lethality.

Further research will be needed to understand exactly how this genetic variation influenced disease severity.

What does this change about the history of plague?

The findings overturn a key assumption in archaeology and infectious disease research.

Scientists had generally believed that large-scale plague outbreaks emerged only after humans began living in densely populated settlements and early cities, where infectious diseases could spread more easily.

Instead, the new evidence suggests that highly mobile hunter-gatherer communities also experienced devastating epidemics thousands of years before urbanisation.

This indicates that plague was capable of spreading and causing widespread deaths even in relatively small prehistoric populations.

What is Yersinia pestis?

Yersinia pestis is the bacterium responsible for plague, one of history’s deadliest infectious diseases.

It is best known for causing the Black Death, which killed tens of millions of people across Europe, Asia, and North Africa during the 14th century.

Today, plague still exists in some parts of the world, though modern antibiotics make it treatable when diagnosed early.

What does the study mean for future research?

The discovery offers researchers new clues about how plague evolved over thousands of years.

It also raises new questions about the following:

• How ancient plague strains spread between communities.
• Whether similar outbreaks occurred elsewhere in prehistoric Eurasia.
• How the bacterium evolved into the forms responsible for later pandemics.
• Why this ancient strain appears to have been especially deadly despite lacking previously recognized virulence genes.

Future archaeological DNA studies may reveal additional early plague outbreaks and reshape scientists’ understanding of humanity’s long relationship with infectious disease.

The bottom line

The discovery of a previously unknown plague strain in prehistoric Siberia pushes the history of deadly plague back to about 5,500 years ago and challenges the belief that devastating epidemics began only after humans settled in cities. Instead, the findings suggest mobile hunter-gatherer communities were already facing lethal outbreaks, offering a new perspective on the early evolution of one of history’s most feared diseases.

Suggested internal links

• Your coverage of major archaeological discoveries.
• Explainer on the Black Death and its global impact.
• Stories about ancient DNA research.
• Coverage of prehistoric human migration.
• Health explainers on emerging infectious diseases.

Suggested external sources

• Nature (original research paper).
• University of Oxford.
• Popular Science.
• World Health Organization (WHO).
• US Centres for Disease Control and Prevention (CDC).

Fact-checking reminders

Before publication, verify:

• The publication date and title of the Nature study.
• The ages of the archaeological remains.
• The estimated age of the newly identified Yersinia pestis strain.
• Quotes attributed to co-author Ruairidh Macleod.
• The locations of the archaeological sites near Lake Baikal.