Siberian Hunter-Gatherers Also Died in Mass Plague Outbreaks 5,500 Years Ago

The plague, one of the deadliest infectious diseases in human history, broke out in a Siberian Neolithic hunter-gatherer community 5,500 years ago—long before the emergence of agricultural societies and cities—causing numerous deaths, particularly among children, a study has revealed.

An international research team, including Professor Eske Willerslev of the University of Copenhagen in Denmark and Dr. Ruairidh Macleod of the University of Oxford in the UK, announced on Thursday in the scientific journal Nature that they have confirmed traces of two plague outbreaks that occurred about 5,500 years ago by analyzing the DNA of human bones found at four hunter-gatherer cemeteries near Lake Baikal in East Siberia.

Professor Willerslev said that the team reconstructed the plague outbreaks within prehistoric hunter-gatherer groups by combining genetic, archaeological, and radiocarbon dating evidence, adding, "These findings demonstrate that even the earliest forms of plague strains were already highly lethal."

The plague is historically known as a deadly epidemic that claimed tens of millions of lives, commonly associated with rats, fleas, densely populated cities, and the Black Death pandemic that swept through medieval Europe.

The research team pointed out that the oldest plague strains identified until now were found in prehistoric European human remains dating back about 5,300 years, and because these strains lacked some key virulence factors that cause the deadly bubonic plague, there had been debate over how lethal they actually were.

In this study, the research team extracted and analyzed ancient DNA from tooth samples of 46 Late Neolithic hunter-gatherers buried in four cemeteries in the western and northern regions of Lake Baikal.

As a result, the plague-causing bacterium (Yersinia pestis) was detected in 18 individuals, representing 39% of those examined.

The research team stated that this infection detection rate is higher than the figures reported from medieval plague mass graves.

Radiocarbon dating and genomic analysis confirmed cases of plague infection in this region during two periods, estimated to be approximately 5,520 to 5,265 years ago and 5,315 to 4,235 years ago.

The research team explained that they secured evidence suggesting the early plague caused significant mortality by comprehensively analyzing the genetic relationships, times of death, and burial patterns of the infected individuals.

Genomic analysis revealed cases of infection within family units, and in some graves, close relatives such as young sisters, cousins, and parents and children were found buried together.

The research team noted that, in particular, the two largest cemeteries showed an abnormally high proportion of child and adolescent deaths, with children aged 8 to 11 accounting for a significant portion of the plague victims, which is highly unusual compared to the typical mortality patterns in nearby cemeteries.

They added that this suggests family-unit infections and person-to-person transmission, with the first outbreak likely occurring within a single generation.

Furthermore, the analysis showed that the early plague strains lacked the gene (ymt) that enables the transmission of bubonic plague via fleas, as well as some key virulence factors, suggesting that it may not have been a typical flea-borne bubonic plague.

Genomic analysis confirmed that these plague strains belong to a lineage older than all currently known ancient and modern plague strains.

The research team stated that there is archaeological evidence that the Lake Baikal hunter-gatherers at the time hunted marmots, which remain a major natural reservoir for plague today, suggesting that the early outbreaks likely began as a zoonotic disease spilling over from infected marmots to humans.

Dr. Macleod said, "These findings represent the oldest evidence of a plague outbreak identified to date. This suggests that the plague broke out much earlier than previously known and was indeed highly lethal."

He added, "These results also challenge the existing hypothesis that high population density and agricultural life are essential conditions for plague pandemics, and demonstrate how long zoonotic diseases have played an important role in human history."

(Photo courtesy of Vladimiri Bazaliiskii, Yonhap News)
※ Please note: This article was translated by AI and may contain errors.