Although best known as a plague that killed millions of Europeans from 1346 to 1353, the Black Death originated about a decade earlier in Central Asia, according to a new study.
A strain of the plague Yersinia pestis bacterium that killed people in what is now Kyrgyzstan in 1338 and 1339 was a common ancestor of four Y. pestis strains previously linked to Europe’s deadly epidemic, say archaeogeneticist Maria Spyrou of the Eberhard Karls University of Tübingen in Germany and her colleagues.
Spyrou’s group identified Y. pestis DNA in the teeth of three individuals from an ancient cemetery in Central Asia where inscriptions on headstones indicate that they, along with many others buried there, died in 1338 and 1339 of a ” plague” unspecified. Comparisons of this genetic material with modern and historical samples of Y. pestis The DNA indicates that the People in Central Asia perished from an early version of the plague bacteria that would wreak havoc in Europethe Middle East and North Africa to the early 1800s, scientists report June 15 at Nature.
“The place and time of the source of the appearance of this plague was most probably in Central Asia in the first half of the 14th century,” Spyrou said during a June 14 press briefing.
The origins of the Black Death, or bubonic plague, have long been debated. What is certain is that Y. pestis is transmitted to humans by fleas that live on rodents. A current proposal argues that the plague bacterium originated in East Asia and was carried across the continent from the 1200s with the expansion of the Mongol Empire. This scenario relied on genetic evidence from European Black Death victims and written accounts of an unidentified plague outbreak encountered by Mongol invaders of Baghdad in the 1200s.
But the earliest archaeological and genetic clues to where and when the Black Death originated come from Central Asia, Spyrou says. Excavations in two cemeteries in northern Kyrgyzstan nearly 140 years ago revealed gravestones indicating that many people buried there in 1338 and 1339 had died of an unknown epidemic. The cemeteries were in use from the mid-1200s to the mid-1300s, but inscriptions on the headstones indicated that deaths increased in 1338 and 1339. Of 467 dated headstones, 118 mark deaths during these two years.
Spyrou’s group was able to reconstruct the whole Y. pestis genome of two of three Central Asian individuals who died in 1338 or 1339 and whose teeth contained remnants of bacterial DNA. Comparisons with modern 203 genetic instructions Y. pestis samples and 47 Y. pestis samples dating from the 14th to 19th centuries identified the Central Asian genomes as a single strain that was a direct ancestor of the Black Death strains.
The researchers also found that marmots and other rodents now living in the same region of Central Asia carry forms of Y. pestis closely related to the old variant. The Y. pestis A variant that killed Central Asians in 1338 and 1339 may therefore have emerged locally, investigators suggest.
The reasons for the rise of a particularly deadly form of Y. pestis in Central Asia in the early 1300s remain unclear. The oldest known Y. pestis strain, which dates back approximately 7,100 years to Eastern Europe, lacked a plague-inducing gene that allows rapid transmission of fleas to humans (SN: 06/29/21).
Spyrou’s group convincingly traces the origin of Y. pestis strains implicated in the Black Death in Europe in Central Asia, says evolutionary biologist Nils Stenseth of the University of Oslo, who was not involved in the study. He sees the new findings as consistent with a scenario in which periods of hot weather in Central Asia triggered repeated plague outbreaks in Europe beginning in the 1300s (SN: 02/23/15). Troops, travelers and merchants moving trade routes from Asia continued to bring plague to Europesuspects Stenseth.
While the newly identified Y. pestis The strain appears to be an ancestor of later European strains, the clear origins of the Black Death – and other pandemics including COVID-19 – are notoriously hard to pin down, says evolutionary geneticist Hendrik Poinar of McMaster University in Hamilton , in Canada.
For example, it will be difficult to determine whether the former Y. pestis the Central Asian strain existed even earlier over a wide swath of the continent, he says. If so, then a precursor strain of the Black Death may have appeared before 1338 in a still undetermined part of Asia. Temptations to translate ancient DNA findings into a story of the Black Death’s precise place and time of origin “must be tempered”, he says.