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Study published in the journal Nature shows that the bacterium Yersinia pestis was already circulating among hunter-gatherers in Siberia thousands of years ago
A scientific discovery of great historical impact revealed the oldest known plague outbreak to date.
Researchers identified traces of the bacterium Yersinia pestis in the bones and teeth of hunter-gatherers who lived about 5,500 years ago in southeastern Siberia, near Lake Baikal.
The discovery was published in the journal Nature and shows that the disease circulated long before the great medieval epidemics, such as the Black Death of the 14th century.
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The data also indicate that entire communities were affected by successive waves of the bacterium, leaving marks in cemeteries with family graves and a large number of dead children.
According to the researchers, the analysis helps to recount the origin of the plague and shows that the disease may have originated in groups with intense contact with wild animals.
Ancient DNA reveals devastating outbreak in Siberia
The scientific investigation analyzed human remains found in cemeteries from the end of the Stone Age, in the region of the Angara River, northwest of Lake Baikal.
According to the study published in Nature, 42 hunter-gatherers had their teeth and bones analyzed by an international team.
Of this total, 18 individuals showed DNA of Yersinia pestis, the bacterium responsible for the plague.
This number represents 39% of the skeletons tested, a figure considered significant by the researchers.
The evidence indicates that the disease hit these communities in at least two different waves.
The first would have occurred about 5,500 years ago.
The second appeared between 400 and 600 years later, reinforcing the hypothesis that the bacterium circulated for a long time in the region.
Raw marmots may explain the origin of the contagion
The possible origin of the outbreak is linked to contact with wild animals, especially infected marmots.
According to information cited by The Guardian, researchers consider that the consumption of raw marmots may have contributed to the emergence of the contamination.
This hypothesis is strengthened because hunter-gatherers lived in constant contact with different non-domesticated species.
In this way, exposure to natural reservoirs of the bacteria could be greater than in ancient agricultural communities.
The scientists also state that new studies will be necessary to clarify all stages of transmission.
Children appear among the main victims of the plague
One of the most striking points of the discovery is the number of child skeletons found in the cemeteries.
At the site of Ust-Ida, located on the banks of the Angara River, many bodies were in shared graves with siblings or other family members.
In two cemeteries analyzed, at least two-thirds of the deceased were under 15 years old.
According to the researchers, children may have been especially vulnerable to the bacteria.
The Yersinia pestis found in these human remains carried a superantigen, a toxic protein capable of causing severe immune reactions.
Thus, the risk of more severe forms of the disease could be higher among the younger ones.
Ancient plague was different from the medieval Black Death
The discovery also shows that the Stone Age plague was not exactly the same as the disease that devastated medieval Europe.
The 14th-century Black Death became known for transmission associated with fleas and rodents.
However, the bacterial DNA found in the Lake Baikal skeletons did not present genes linked to this type of transmission.
Even so, the bacteria already had the potential to cause different forms of the disease.
Among them were pneumonic plague, which affects the lungs, septicemic plague, linked to the blood, and bubonic plague, marked by swelling in the lymph nodes.
Therefore, experts still discuss the level of lethality of this early form of the plague among adults.
Discovery changes understanding of the disease’s origin
The international team involved researchers from Copenhagen, Alberta, Cambridge, and London.
Initially, the goal was not to find the origin of the most famous plague in history.
The analysis of the skeletons ended up revealing a much older chapter in the trajectory of Yersinia pestis.
According to Samuel Cohn, a professor of medieval history at the University of Glasgow, the discovery makes sense from a historical perspective.
For him, hunter-gatherers had contact with many more wild species than early farmers.
Thus, these groups could have been more frequently exposed to the natural reservoirs of the disease.
What does the discovery reveal about human history?
The new analysis shows that the plague was already able to reach small and isolated communities thousands of years before the medieval urban epidemics.
This data is important because the Black Death is usually associated with densely populated cities, rats, and poor sanitary conditions.
The cemeteries of Lake Baikal indicate that the bacteria also circulated in dispersed prehistoric groups.
The presence of family graves suggests that the disease may have had profound impacts on the organization of these communities.
Scientists are still seeking new answers
Despite the advances, researchers still want to better understand how these outbreaks occurred.
The exact transmission, the role of marmots, and the lethality of the ancient bacteria remain under investigation.
Even so, the study published in Nature already represents a milestone for archaeogenetics.
The analysis of DNA preserved in 5,500-year-old bones shows that the history of the plague is older, more complex, and more surprising than previously thought.
Now, science begins to rewrite one of the most important chapters in the relationship between infectious diseases, wild animals, and human societies.
Do you think discoveries like this help to better understand current pandemics or show that humanity has always lived with invisible threats from nature? Leave your opinion!
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