DNA Evidence Shows Plague Struck Humans 5500 Years Ago

For countless individuals today, the term plague immediately evokes images of rodents, densely populated medieval settlements, and the catastrophic outbreaks that ravaged Europe throughout the Middle Ages and subsequent centuries.Fresh scientific investigations indicate that the lethal trajectory of

For countless individuals today, the term plague immediately evokes images of rodents, densely populated medieval settlements, and the catastrophic outbreaks that ravaged Europe throughout the Middle Ages and subsequent centuries.

Fresh scientific investigations indicate that the lethal trajectory of this illness extends considerably further into the past. A detailed examination appearing in the journal Nature demonstrates that plague was already responsible for fatalities among human populations approximately 5,500 years in the past, occurring within modest communities of hunter-gatherers long prior to the development of agricultural societies or urban centers.

A global group of experts analyzed preserved genetic material extracted from skeletal remains discovered at four ancient burial grounds associated with hunter-gatherer populations located near Lake Baikal in the region of East Siberia. Through the process of decoding bacterial genetic sequences retained within ancient dental structures, the investigators were able to rebuild complete pathogen genomes and detect previously unidentified early variants of the plague bacterium.

Prehistoric Plague Events Uncovered Through Genetic Study

The scientists integrated molecular data with evidence from excavation sites along with precise dating techniques to reconstruct events that unfolded in these ancient societies. Lead researcher Ruairidh Macleod, who performed the analysis during doctoral studies at the University of Cambridge and currently serves as a Research Fellow at the University of Oxford, noted that the combination of plague genetic markers, familial connections among the deceased, excavation details, and chronological data produced an exceptionally clear account of the epidemic events.

Genetic traces of Yersinia pestis, the microorganism that causes plague, appeared in 18 out of the 46 examined individuals. This infection rate approaches 40 percent among the studied remains, surpassing infection detection levels observed at certain medieval plague sites according to the research team.

Indications of High Lethality in Early Plague Forms

Prior investigations had suggested that prehistoric variants of Yersinia pestis were missing several genetic elements that later enabled efficient transmission of bubonic plague via fleas and rodent carriers. Consequently, many experts had assumed that the initial manifestations of the disease would not have produced widespread or fatal epidemics.

The current results point toward an opposing conclusion. At the two most extensive burial locations, investigators observed a disproportionately high proportion of juveniles and adolescents among those interred. Archaeologists had long been puzzled by this demographic pattern over many years.

University of Alberta archaeologist Andrzej Weber, who leads the Baikal Archaeology Project, explained that the elevated presence of young individuals combined with the compressed timeframe had remained an unresolved question since the 1990s, and discovering plague as the underlying factor provides a compelling explanation.

Chronological analysis through radiocarbon methods showed that numerous interments occurred within a narrow temporal window. In several instances, siblings or parent-child pairs appear to have perished nearly simultaneously and received joint burial.

Distinct Genetic Element Possibly Heightened Disease Impact

The investigation also uncovered a unique superantigen within the ancient plague variants. This genetic component responsible for toxin production has not been identified in subsequent historical plague strains. Superantigens are capable of provoking intense immune activations and are associated with pronounced inflammatory effects, which could render infections considerably more hazardous.

Senior author Martin Sikora, Associate Professor at the University of Copenhagen, stated that this discovery alters perceptions of initial plague epidemics, indicating that even prior to the evolution of effective flea-based transmission, these early strains possessed a powerful array of virulence factors capable of rendering infections extremely deadly.

The findings imply that some of the oldest documented plague outbreaks could have been equally destructive as later versions of the illness, especially among younger populations, even without the flea-mediated spread mechanisms typical of bubonic plague.

Insights Into Plague Emergence and Spread

The research further bolsters the hypothesis that plague originated in Central or North-East Asia prior to dissemination throughout Eurasia via wild rodent reservoirs. Excavation records suggest that the studied hunter-gatherer groups maintained close interactions with marmots, sizable burrowing rodents that continue to harbor plague in contemporary times. Scientists propose that the pathogen likely transferred directly from infected marmots to humans, initiating outbreaks within these prehistoric groups.