A large-scale study tracing human disease history back 37,000 years has identified harmful bacteria, viruses and parasites that have afflicted humans for millennia, uncovering the earliest evidence of the plague bacterium from about 5,500 years ago.
Researchers analyzed DNA from bones and teeth of 1,313 individuals who lived across Europe and Asia — known collectively as Eurasia — from the Early Stone Age, roughly 12,500 years ago, up to about 200 years ago. The oldest sample dates back 37,000 years.
The study found the earliest evidence of zoonotic diseases — illnesses transmitted from animals to humans — emerging around 6,500 years ago and becoming more widespread about 1,500 years later.
“We’ve long suspected that the transition to farming and animal husbandry opened the door to a new era of disease. Now DNA shows us that it happened at least 6,500 years ago,” said Professor Eske Willerslev of the universities of Cambridge and Copenhagen.
“These infections didn’t just cause illness — they may have contributed to population collapse, migration and genetic adaptation.”
The research detected the world’s oldest genetic trace of Yersinia pestis, the bacterium that causes plague, in a sample dating back 5,500 years. The plague is estimated to have killed between one-quarter and one-half of Europe’s population during the Middle Ages.
“It is simply the oldest example of plague we have seen to date,” said Frederik Seersholm of the University of Copenhagen.
“When you look at this finding, you can really see how plague evolved over time toward the version we know from ‘The Black Death’ — the pandemic that hit Europe from 1346 to 1353 and killed up to 40% of the population in some areas.”
Traces of other diseases were also found: diphtheria dating back 11,000 years, hepatitis B about 9,800 years ago and malaria 4,200 years ago. In total, researchers identified 214 known human pathogens in prehistoric Eurasian populations.
The study was published Wednesday in the journal Nature.
Professor Astrid Iversen of the University of Oxford said zoonoses “really took off” about 5,000 years ago.
“Zoonoses first became a major problem for humans when we started keeping animals together in large herds and living close to these animals,” Iversen said.
“This meant animals could more easily infect each other, increasing the risk of transmitting diseases to humans.”
Martin Sikora, first author from the University of Copenhagen, said understanding how diseases evolved in the past “can help us prepare for the future.”
Willerslev agreed, saying mapping ancient diseases can aid vaccine development.
“You can see when a virus or bacterium has mutated, how quickly the genome has changed and which mutations were significant,” Willerslev said. “Mutations that were successful in the past are likely to reappear.”
