HEALTH – The pandemic Plague black, which decimated much of the European population in the Middle Agesit arose in Central Asia, in present-day Kyrgyzstan, according to a study that puts an end to almost seven centuries of questioning.
It was thanks to ancient human DNA, extracted from a 14th-century cemetery in northern Kyrgyzstan, that the researchers were able to trace the source. Their discoveries, published this Wednesday, June 15, in the journal Naturethey resolve a long-standing debate among historians.
the epidemic of Plague Black arrived in Europe in 1346 through the Mediterranean basin, through ships carrying merchandise from the Black Sea. In just eight years, the “black death” killed up to 60% of the population of Europe, the Middle East and North Africa. And it marked the beginning of a long wave of the epidemic, which would resurface on and off for 500 years.
Where was he born? One of the most commonly advanced clues was from China, but no hard evidence could support this theory. “I have always been fascinated by the Black Death, and one of my dreams was to solve the mystery of its origins,” disaster historian Phil Slavin, one of the study’s authors, told a news conference.
“Death of pestilence”
This professor at the University of Stirling (Scotland) knew of the existence of two medieval cemeteries near Lake Issyk Kul in Kyrgyzstan, which had been excavated at the end of the 19th century.
Of more than 400 tombstones, one hundred were precisely dated: 1338-1339. With an epitaph mentioning an elliptical “death of pestilence”, in Old Syriac. So many signs of abnormal excess mortality within a community, seven or eight years before the Black Death hit Europe.
To find the cause of death, the researchers looked at the dental DNA of seven skeletons. “The dental pulp is a valuable source, because it is a highly vascularized area that gives a high probability of detecting pathogens in the blood,” explained Maria Spyrou, from the University of Tübingen in Germany, also an author of the study.
The DNA could be sequenced, a tricky job as it was fragmented, and then compared to a database containing the genomes of thousands of bacteria. Verdict: The bodies had been infected with the bacterium Yersinia pestis, the bacillus responsible for the Black Death, transmitted to humans by rodent fleas. Therefore, this community had been the victim of the same scourge that struck Europe a few years later.
Analysis of the Yersinia pestis genome also revealed that it was an ancestral strain of the bacterium. The one that is at the base of the “genetic tree” of the plague. Scientists rightly associate the appearance of the Black Death in Europe with a genetic “Big Bang” during which the mother bacteria diversified massively.
In the heart of the Silk Roads
The strains discovered in Kyrgyzstan are exactly “at the crux of this massive diversification”, which occurred around the 1330s. Confirming that this region of the world, Tian Shan, was indeed the starting point of the expansion, according to Maria Spyrou .
Furthermore, in rodents living today in the Tian Shan, the researchers identified a strain of the bacteria very close to that of the human victims of 1338-1339, “the closest that has ever been found in the world,” added Johannes Krause, of the Max Planck Institute, co-author of the study.
These were Christian communities, ethnically diverse (Mongols, Uyghurs…), who practiced a long-term trade based on the funerary objects found: pearls from the Pacific, corals from the Mediterranean, silk dresses… “Living in the heart of the Silk Roads, they must have traveled extensively, which played a role in spreading the epidemic across the Black Sea,” says Phil Slavin.
The plague has never been eradicated from the face of the Earth: every year thousands of people continue to be infected, especially in Central Asia. In the Tian Shan mountains, marmots are the main animal reservoir of the disease.
Fortunately, a deadly pandemic like the one in the Middle Ages is not to be feared: not because the bacteria are less virulent, but because hygiene conditions and the use of antibiotics have nothing to do with the past.
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