Scientists have identified the earliest evidence of plague known so far: traces of bacterial DNA in the teeth of hunter-gatherers buried near Lake Baikal in Siberia. Carbon dating indicates that the disease caused outbreaks about 5,500 years ago, about 200 years earlier than previously thought.
Finding in Siberia
A team led by geneticist Eske Willerslev of the University of Copenhagen analyzed remains from four cemeteries. They found traces of Yersinia pestis in the teeth of 18 individuals. The dating revealed two episodes of infection.
“To understand our own history, understanding the history of the plague is extremely important,” Willerslev said.
The prehistoric plague spread in stages. According to the authors, it was probably transmitted from marmots—native rodents—when people consumed their raw organs or handled infected skins. It also spread from person to person through coughing or sneezing.
Many of the deceased were children between 8 and 11 years old. Three girls were buried together; two were cousins. An aunt and her nephew were found in another mass grave. “There were people who buried the dead and who knew who they were. It’s a very human element,” said co-author Ruairidh Macleod, an expert in ancient DNA at the University of Oxford.
Implications of the study
The researchers note that children may be at greater risk due to still developing immune systems. The presence of multiple victims suggests that the prehistoric plague caused both isolated cases and outbreaks, said geneticist Aida Andrades Valtueña, from the Max Planck Institute for Evolutionary Anthropology, who was not involved in the study.
This ancient strain evolved long before the bubonic plague responsible for the medieval Black Death. However, there is evidence that earlier plagues were just as serious. The disease not only affected populous cities, but also small nomadic groups.
“Understanding the steps the bacteria took to become the deadly pathogen we know today can provide clues about how pathogens could emerge in the future,” wrote Andrades Valtueña.
The study was published Wednesday in the journal Nature.
