When most people hear the word “plague,” they picture rats, crowded medieval towns, and huge death waves that swept Europe long ago.
New research shows the disease was deadly much earlier. A study in Nature found plague killing people 5,500 years ago, before farms and cities even existed.
Scientists looked at ancient DNA from human teeth found in four burial sites near Lake Baikal in Siberia. By reading the genetic code inside the teeth, they rebuilt the DNA of the plague bacteria and discovered old, unknown strains.
Ancient DNA Shows Prehistoric Plague
Combining DNA clues with archaeology and radiocarbon dating, the team pieced together what happened in those early villages.
Out of 46 people studied, 18 showed DNA from Yersinia pestis, the bacterium that causes plague. That is about 40 % of the sampled individuals, a higher rate than many medieval sites.
Early Plague Was Very Deadly
Earlier scientists thought ancient plague strains were weak because they lacked genes that let the disease spread easily through fleas. They believed early outbreaks could not be large or fatal.
The new data tell a different story.
In the two biggest cemeteries, many of the dead were children and young teens. Archaeologists have long wondered why so many youngsters were buried there.
"The high number of children and the short time span was a real puzzle. Finding that plague caused it makes perfect sense," says archaeologist Andrzej Weber, leader of the Baikal project.
Radiocarbon dates show that many burials happened within a short period. Sometimes whole families – parents and children – were buried together.
A Unique Toxin May Have Made It Worse
The scientists also found a special superantigen in the ancient plague DNA. This toxin is not present in later historic strains.
Superantigens can trigger huge immune reactions, leading to severe inflammation and making infections far more dangerous.
These findings suggest that the earliest known plague outbreaks could have been as lethal as later ones, especially for kids, even though the disease did not yet spread through fleas.
Where the Plague Came From
The study supports the idea that plague first appeared in Central or North‑East Asia and then traveled across Eurasia via wild rodents.
Archaeological clues show the hunter‑gatherers often dealt with marmots – large burrowing rodents that still carry plague today. The disease may have jumped directly from infected marmots to humans, sparking the ancient outbreaks.