Ancient Siberian graves discovered by scientists have revealed the oldest traces of one of humanity’s deadliest diseases: the plague, challenging established beliefs about its origins.
Examinations — published in the journal Nature on Wednesday — on skeletons of hunter-gatherers who lived some 5,500 years ago in the Lake Baikal region of Siberia revealed DNA traces of the bacteria that cause the plague.
The plague has led to several devastating pandemics over centuries, most famously the “Black Death,” which killed more than 25 million people across Europe in the mid-1300s.
The discovery suggests that the infectious disease — which scientists had thought began as a mild illness — posed a lethal threat to humanity far sooner than was previously believed.
“The findings fundamentally change how we think about the origins and early impact of one of humanity’s most consequential pathogens,” evolutionary geneticist Eske Willerslev of the University of Copenhagen and the University of Cambridge, and senior author of the study, told Reuters.
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“It doesn’t fit the model,” Willerslev also told the New York Times, “But we have to accept the data.”
The researchers said the outbreak was particularly deadly for young people, judging from the burial sites that included children, and attributed this to genetic traits in these strains that are no longer found in today’s iteration of the pathogen.
At Lake Baikal, the bacterium Yersinia pestis, which causes the plague, was detected in 18 of 46 bodies examined, a higher rate than in some medieval plague burial pits. University of Oxford evolutionary geneticist and study lead author Ruairidh Macleod said finding evidence of a large-scale lethal plague outbreak among these hunter-gatherers was a “complete surprise.”
He also noted that the ancient strains lacked a gene required for efficient flea-borne transmission but possessed a genetic variant absent in later plague strains that can cause severe inflammatory complications to which children are especially vulnerable. Many of those buried were children, sometimes siblings.
According to a 2020 study published in the National Library of Medicine, the plague has killed 200 million people in all of human history, with experts having chronicled enormous pandemics dating back to the Roman Empire. Its rise was seemingly tied to the emergence of farming and cities, where animals, food and humans would interact in close proximity, but novel findings suggest this was not necessarily the case, given emerging data on its impact on “prehistoric individuals across Europe.”
There were also thoughts that early strains may have been mild, but the discovery that the plague killed prehistoric hunter-gatherers traversing a remote forested landscape in small bands contradicts those notions.
Experts also said the discovery adds to evidence that marmots were the bacterium’s original host species, and that the plague arose in central or northeastern Asia before spreading across Eurasia.
The disease, which has several common strains, including the bubonic, pneumonic, and septicemic types, now most commonly lives in rodents. However, it’s fleas that pick up the bacterium and spread it to other animals, including humans.
In the world today, a few hundred people contract the disease each year, though it is curable with antibiotics, the Mayo Clinic says.
— with files from Reuters
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