Ancient DNA solves the mystery of the origin of the medieval Black Death

A view of the Tian Shan Mountains in Kyrgyzstan, the region of Central Asia where researchers studying ancient plague genomes have traced the origins of the 14th-century Black Death that killed tens of millions of people, in an undated photograph. (Lyazzat Musralina via Reuters)

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WASHINGTON – The ancient DNA of bubonic plague victims buried in cemeteries along the old Silk Road trade route in Central Asia helped solve an enduring mystery, pinpointing an area in northern Kyrgyzstan as a starting point for the Black Death that killed tens of millions of people in the mid-fourteenth century.

Researchers said Wednesday they recovered ancient DNA traces of the plague bacterium Yersinia pestis from the teeth of three women buried in a medieval Nestorian Christian community in the Chu Valley near Issyk Kul Lake in the foothills of the Tian Shan Mountains, who died in 1338. -1339. The first documented deaths elsewhere in the pandemic date back to 1346.

The reconstruction of the genome of the pathogen showed that this strain not only gave rise to the one that caused the Black Death that tore apart Europe, Asia, the Middle East and North Africa, but also most of the plague strains existing today.

“Our discovery that the Black Death originated in Central Asia in 1330 silences centuries-old debates,” said historian Philip Slavin of the University of Stirling in Scotland, co-author of the study published in the journal Nature.

The Silk Road was an overland route for caravans carrying a panoply of goods back and forth from China through the lavish cities of Central Asia to points including the Byzantine capital Constantinople and Persia. It could also have served as a conduit for death if the pathogen had hitchhiked the trailers.

“There have been several hypotheses suggesting that the pandemic may have originated in East Asia, particularly China, Central Asia, India, or even close to where the first outbreaks were documented in 1346 in the Black Sea regions and of the Caspian Sea, “said the archaeologist and lead author of the study Maria Spyrou of the University of Tübingen in Germany.

“We know that trade was probably a factor in the dispersal of the plague in Europe during the onset of the Black Death. It is reasonable to assume that similar processes led to the spread of the disease from Central Asia to the Black Sea between 1338 and 1338. 1346, “added Spyrou.

The origins of the pandemic are strongly contested, as evidenced by the debate on the emergence of the current COVID-19 pandemic.

Already in medieval times we see the high mobility and rapid spread of a human pathogen. … We should not underestimate the potential of pathogens to spread around the world from rather remote places.

– Study co-author Johannes Krause

The Black Death was the deadliest pandemic on record. According to Slavin, it may have killed 50% to 60% of the population in parts of Western Europe and 50% in the Middle East, resulting in an estimated 50-60 million deaths. An “inexplicable number” of people also died in the Caucasus, Iran and Central Asia, Slavin added.

“Already in the Middle Ages we see the high mobility and rapid spread of a human pathogen,” said Johannes Krause, archaeologist and co-author of the study, director of the Max Planck Institute for the Science of Human History in Germany. “We shouldn’t underestimate the potential for pathogens to spread around the world from quite remote locations, possibly due to a zoonotic event” – an infectious disease that passes from animals to people.

The researchers analyzed the teeth, a rich source of DNA, of seven people buried in cemeteries in communities called Burana and Kara-Djigach, obtaining DNA from three plague in Kara-Djigach.

The cemeteries, excavated in the 19th century, included tombstones that attributed deaths to the “plague” in the Syriac language. Items such as pearls, coins, and clothing from remote places indicated that cities were involved in international trade, possibly offering stopping services for long-distance caravans.

Bubonic plague, untreatable at the time but now treatable with antibiotics, caused swollen lymph nodes with bleeding and pus, with the infection spreading to the blood and lungs.

In Europe, it was mainly transmitted through flea bites carried on infected rats. The pandemic originated in wild rodents, most likely marmots, a type of ground squirrel, Slavin said. Rodents crawling into caravans may have helped spread it, but other transmission mechanisms may have included human fleas and lice.

“We found that the closest living relatives of that strain of Y. pestis that gave rise to the Black Death are still found in marmots in that region today,” Krause said.

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