Scientists have discovered the oldest known evidence of the plague, with findings suggesting the disease emerged approximately 5,500 years ago. This discovery predates previous estimates by about 200 years.
The plague, caused by Yersinia pestis bacteria, has a long history of causing deadly outbreaks, including the Black Death that significantly impacted Europe in the 14th century. While rare today, the plague can still be treated with antibiotics.
Researchers analyzed remains from four cemeteries near Siberia's Lake Baikal, searching for traces of the plague-causing bacteria. They identified remnants of plague DNA in the teeth of 18 ancient hunter-gatherers. Radiocarbon dating of the bones indicated that the plague caused two distinct outbreaks, with the earliest cases appearing around 5,500 years ago.
The study, published in the journal Nature, suggests that this prehistoric form of the plague evolved in stages and affected small family groups. It is believed to have spread from marmots, large rodents, likely through human consumption of raw organs or contact with infected hides during butchery. Transmission between people may have also occurred through respiratory droplets from coughing and sneezing.
Analysis of the remains revealed that young children, particularly those aged 8 to 11, were disproportionately affected. The burial patterns, which showed individuals like three young girls and an aunt and nephew buried together, suggest a familial or close-knit community context. Researchers noted that children might have been more vulnerable due to less developed immune systems.
The presence of multiple victims in close proximity indicates the ancient plague's capacity to cause both individual infections and community-wide outbreaks. This prehistoric plague predates the bubonic plague responsible for the Black Death, yet evidence suggests it was equally devastating, impacting not only densely populated areas but also small, nomadic groups.
Understanding the historical progression of the plague can provide insights into how pathogens evolve into dangerous diseases and potentially offer clues about how new diseases might emerge in the future.