An engraved headstone of a person who died of the Black Death Plague in Kara-Djigach Cemetery in present-day Kyrgyzstan. Credit: P.-G. Bourbon, MA Spyrou et al./Nature
A Silk Road scale could have been the epicenter of one of humanity’s most destructive pandemics.
People who died in a 14th-century outbreak in present-day Kyrgyzstan were killed by strains of the plague-causing bacterium. Yersinia pestis which led to the pathogens responsible several years after the Black Death, shows a study of ancient genomes.
“It’s like finding the place where all the strains come together, like the coronavirus where we have Alpha, Delta and Omicron from this strain in Wuhan,” says Johannes Krause, a paleogenetic at the Max Planck Institute for Evolutionary Anthropology in Wuhan. Leipzig. , Germany, who co-directed the study, published on June 15, a Nature1.
Between 1346 and 1353, the Black Death ravaged western Eurasia, killing up to 60% of the population in some places. Historical records suggest that bubonic plague arose from the east: Caffa, on the Crimean peninsula, experienced one of the first recorded plague outbreaks during a 1346 siege by the Mongol Empire’s army. The Caucasus and other places in Central Asia have been proposed as potential epicenters.
China is home to some of the greatest genetic diversity in the modern world I. pestis strains, which hint at an East Asian origin for the Black Death. “There were all kinds of hypotheses in the literature. And we really knew exactly where he was coming from, “says Krause.
Signs of the plague
A few years ago, Philip Slavin, an economic and environmental historian at the University of Stirling in the United Kingdom and co-author of the study, found records of a couple of 14th-century cemeteries in Kyrgyzstan that he thought could contain clues about the origins of the Black Death. The cemeteries, known as Kara-Djigach and Burana, contained an unusually large number of tombstones dating from 1338 to 1339, ten of which made explicit reference to a pestilence.
“When you’re one or two years old with excess mortality, it means something funny is going on,” Slavin told a news conference.
To determine whether the burials had any relevance to the subsequent Black Death, Slavin worked with Krause to locate the remains of the Kyrgyz cemetery, which had been excavated in the 1880s and 1890s and moved to St. Petersburg, Russia. The team, led by archaeogenetist Maria Spyrou of the University of Tübingen, Germany, sequenced the ancient DNA of seven people whose remains were recovered, discovering I. pestis DNA in three Kara-Djigach burials.
Credit: Lyazzat Musralina
A couple of full I. pestis The genomes collected from the data showed that the bacteria were direct ancestors of strains linked to the Black Death, including a I. pestis sample of a person who died in London that Krause’s team sequenced in 2011. The Kara-Djigach strain was also an ancestor of the vast majority of I. pestis today’s lineages, a sign, says Krause, of an explosion I. pestis diversity shortly before the Black Death. “It was like a big plague explosion,” he told a news conference.
Other evidence places the origins of the Black Death in this part of Central Asia. Among the modern strains of I. pestis Bacteria, groundhog sampling, and other rodents in Kyrgyzstan, Kazakhstan, and Xinjiang in northwestern China, around the Tian Shan Mountains, were more closely related to the Kara-Djigach strain. “We can’t really say it’s that town or that valley, but it’s probably that region,” Krause says.
Rodents are the natural reservoir of I. pestis, and humans develop bubonic plague only when a vector such as fleas transmits the infection. Krause suspects that close human contact with infected groundhogs caused the Kyrgyz epidemic, while immunologically naive rat populations in Europe fed the black plague.
Tian Shan makes sense as the epicenter of the Black Death, says Slavin. The region is located on the ancient trade route of the Silk Road, and the tombs of Kyrgyzstan were found to contain pearls from the Indian Ocean, corals from the Mediterranean, and foreign coins, suggesting that goods passed through the area. distant. “We can hypothesize that trade, both long-distance and regional, must have played an important role in the spread of the pathogen to the west,” Slavin said.
Medieval “death certificates”
Obtaining genomes from ancestral plague bacteria behind black plague is “a breakthrough,” says Monica Green, a medieval historian and independent scholar from Phoenix, Arizona. “The tombstones are as close as ever to the ‘death certificates.’ So we know this lineage of I. pestis it existed then ”. But she is less certain of the study’s conclusion that the “big bang” of the plague occurred around the time of Kyrgyzstan’s deaths in 1338-39. Green has hypothesized, based on genetic evidence, that the expansion of the Mongol Empire in the 13th century catalyzed the expansion and diversification of I. pestis strains responsible for the subsequent black plague.
Sharon Dewitte, a bioarchaeologist at the University of South Carolina in Colombia, says the work opens the door to the study of the black plague, and the broader outbreak of which it was part, known as the second plague pandemic, more beyond Europe. He is keen to compare the demographic and mortality patterns of people who died of the plague in Kara-Djigach with those of European black plague cemeteries.
“Having more plague samples from ancient Asia and China will be very interesting in terms of adding even more evidence to the Asian origin of the first and second. [plague] pandemics “, adds Simon Rasmussen, a computer biologist at the University of Copenhagen who has analyzed I. pestis sequences.
Krause hopes to analyze the remnants of China to see how a pandemic that so marked Europe resonated in East Asia, he says. “We would love to get the eastern part of the story.”