Centuries-old DNA, taken from the victims of the bubonic plague buried in cemeteries on the ancient Silk Road in Central Asia, has helped unravel the mystery of the disease’s origins. Scientists have identified an area in northern Kyrgyzstan as the starting point for the Black Death, a plague that killed tens of millions in the mid-14th century.
Researchers announced on Wednesday that they had taken DNA traces from the plague bacterium Yersinia pestis from the teeth of three women who died in 1338-1339 and were buried in a medieval Nestorian Christian community in the Chu Valley, near Lake Issyk-Kul, at the foot of the Tian-Shan Mountains in Kyrgyzstan. The earliest documented deaths in other areas during that pandemic date back to 1346.
Reconstruction of the genome of the pathogen showed that this strain gave rise to both the one that caused the Black Death, which wreaked havoc in Europe, Asia, the Middle East and North Africa, as well as most of the current plague strains.
“Our discovery that the Black Death originated in Central Asia in the 1330s puts an end to centuries of debate,” said historian Philip Slavin of Stirling University in Scotland, co-author of the study published in the journal Nature. Reuters, taken over by Agerpres.
The deadliest pandemic in history
The Silk Road was a land route traveled by caravans carrying goods back and forth from China through sumptuous cities in Central Asia to various areas, including the Byzantine capital of Constantinople and Persia. It may also have served as a means of spreading the Black Death if the pathogen reached these caravans.
“There have been a number of different hypotheses that have suggested that the pandemic may have occurred in East Asia, especially in China, Central Asia, India, or even close to where the first outbreaks were documented in 1346,” in the Black Sea and Caspian Sea regions, ”said the study’s lead author, Maria Spyrou, an archaeogenetician at Tübingen University in Germany.
“We know that trade was probably a key factor in the spread of the plague in Europe at the beginning of the Black Death. It is reasonable to assume that similar processes led to the spread of Central Asian disease in the Black Sea between 1338 and 1346, “Spyrou added.
The origins of the pandemic are hotly contested, as evidenced by the debate over the current COVID-19 pandemic.
The Black Death was the deadliest pandemic in history. It is said to have killed 50% to 60% of the population in Western Europe and 50% of the population in the Middle East; In all, about 50 to 60 million dead, Slavin said. An “impossible number” of people died in the Caucasus, Iran and Central Asia, the researcher added.
“In the Middle Ages, we already saw high mobility and the rapid spread of a human pathogen,” said archaeogenetic Johannes Krause, co-author of the study and director of the Max Planck Institute for the History of Human History in Germany.
“We should not underestimate the potential of pathogens to spread in the world from quite distant places, probably as a result of a zoonotic event,” he added. Zoonoses are infectious diseases that can be transmitted from animal to human.
How the plague spread to Europe
The researchers analyzed teeth, a rich source of DNA, from seven people buried in the cemeteries of the communities called Burana and Kara-Djigach, and identified plague DNA in the remains of three individuals in Kara-Djigach.
The cemeteries, excavated in the 19th century, included tombstones with Syriac inscriptions attributing the deaths to the “plague”. Objects such as pearls, coins and clothing from distant places suggest that cities were involved in international trade, probably providing services for passing caravans.
Bubonic plague, untreatable at the time but currently curable with antibiotics, causes inflammation of the lymph nodes with blood and pus and spreads the infection to the blood and lungs.
In Europe, the disease was transmitted mainly by flea bites carried by infected rats. The pandemic originated in wild rodents, most likely groundhogs, Slavin said. Rodents that traveled in caravans may have contributed to the spread of the disease, but other transmission mechanisms may have included fleas and lice carried by humans.
“I found that the closest living relatives of that strain Yersinia pestis, which led to the Black Death, are still present in marmots in that region, “said Krause.
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