Old 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 scientists 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 – Ancient DNA from buccaneer buried in cemeteries on the ancient Silk Road in Central Asia has helped solve a lasting mystery, by designating an area in northern Kyrgyzstan as the starting point for the Black Death that killed tens of millions of people in the mid-1300s. the number.

Researchers said Wednesday that they retrieved ancient DNA traces of the Yersinia pestis plague bacterium from the teeth of three women buried in a medieval Nestorian Christian community in the Chu Valley near Lake Issyk Kul at the foot of the Tian Shan Mountains, which perished in 1338-1339. The earliest deaths documented elsewhere in the pandemic were in 1346.

Reconstruction of the genome of the pathogen showed that this strain not only gave rise to the one that caused the black death that shattered Europe, Asia, the Middle East and North Africa, but also to most plague strains that exist today.

“Our finding that the Black Death originated in Central Asia in the 1330s puts centuries-old debates to rest,” 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 variety of goods back and forth from China through the lavish cities of Central Asia to points including the Byzantine capital Constantinople and Persia. It may also have acted as a death canal if the pathogen took a trip on the caravans.

“There have been a number of different hypotheses suggesting that the pandemic may have originated in East Asia, specifically China, Central Asia, India, or even near where the first outbreaks were documented in 1346 in the Black Sea. and Caspian Sea regions., “said archaeogeneticist and study author Maria Spyrou at the University of Tübingen in Germany.

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

The origins of the pandemic are hotly debated, as evidenced by the debate over the emergence of the current COVID-19 pandemic.

Already in the Middle Ages we see high mobility and rapid spread of a human pathogen. … We should not underestimate the potential of pathogens to spread around the world from fairly remote locations.

– Study co-author Johannes Krause

The Black Death was the deadliest pandemic ever recorded. It may have killed 50% to 60% of the population in parts of Western Europe and 50% in the Middle East, for a total of around 50-60 million deaths, Slavin said. An “unexplained 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 archaeogeneticist and co-author Johannes Krause, director of the Max Planck Institute for the Science of Human History in Germany. “We should not underestimate the potential of pathogens to spread around the world from rather remote places, probably due to a zoonotic event” – a contagious disease that jumps from animals to humans.

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

The cemeteries, which were excavated in the 19th century, included tombstones that attributed deaths to “plague” in the Syrian language. Objects such as pearls, coins and clothing from distant places indicated that cities were involved in international trade, perhaps offering stop-and-rest services for long-distance caravans.

The bubonic plague, which could not be treated at the time but is now cured using antibiotics, caused swollen lymph nodes with blood and pus seeping out, and the infection spread to the blood and lungs.

In Europe, it was transmitted mainly through the bite of fleas carried on infected rats. The pandemic occurred in wild rodents, most likely marmots, a type of ground grain, Slavin said. Rodents that notice in caravans may have helped to spread it, but other transmission mechanisms may have included human fleas and lice.

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

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