Ancient DNA Shows Plague Killed Siberians 5,500 Years Ago

Ancient DNA analysis has revealed that the bacterium Yersinia pestis, the causative agent of plague, was present and causing fatalities in hunter-gatherer populations in Siberia as early as 5,500 years ago. This discovery predates the well-known Black Death pandemic by thousands of years and suggests that plague was circulating in human populations long before the development of large, dense urban centers and the establishment of flea-borne transmission cycles. The findings, published in the journal Cell Host & Microbe, challenge previous understandings of plague's historical timeline and its impact on early human societies.

The research team, led by scientists from the University of Copenhagen, analyzed DNA extracted from the remains of individuals found at an archaeological site in the Altai Mountains of Siberia. They identified the presence of Yersinia pestis in several individuals, indicating that plague was a significant cause of death in these prehistoric communities. The genetic makeup of these ancient plague strains also offers clues about their virulence. Researchers found that these early strains carried a specific genetic factor, known as the yersinia pestis plasmin receptor (YPR), which is associated with the ability to provoke a severe immune response in the host. This factor may have contributed to the high mortality rates observed in these ancient populations, potentially leading to the death of entire families.

This finding is significant because it pushes back the known timeline for plague's impact on human health by over 4,000 years. Previously, the earliest evidence for plague in humans dated to the Neolithic period, around 7,000 years ago, but this new study provides more direct evidence of its lethal effects in a specific Siberian population. The presence of plague in hunter-gatherer groups, who were largely nomadic and lived in smaller, dispersed communities, suggests that the disease may have been transmitted through direct contact or other means not solely reliant on the rat-flea-human cycle that characterized later epidemics. The study's authors hypothesize that these early strains might have been more adept at spreading through direct human-to-human contact or via other vectors, contributing to their widespread and deadly nature.

The implications of this research extend to our understanding of human evolution and the co-evolution of pathogens and their hosts. The long-term presence of plague in human populations could have exerted selective pressures, influencing the development of human immune systems over millennia. Further research into the genetic diversity of ancient Yersinia pestis strains and their interactions with different human populations could shed more light on the complex history of this devastating disease and its enduring legacy.