Archaeological and genetic data from a 1330s graveyard point to the bubonic plague’s origin.
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, a new study suggests.
A strain of the plague-causing Yersinia pestis bacterium that killed people in what’s now Kyrgyzstan in 1338 and 1339 was a common ancestor of four Y. pestis strains previously linked to the deadly European outbreak, say archaeogeneticist Maria Spyrou of Eberhard Karls University of Tübingen in Germany and colleagues.
Spyrou’s group identified Y. pestis DNA in teeth of three individuals from an ancient Central Asian cemetery where tombstone inscriptions say that they, as well as many others buried there, died in 1338 and 1339 from an unspecified “pestilence.” Comparisons of that genetic material to modern and historic samples of Y. pestis DNA indicate that the Central Asian folks perished from an initial version of the plague bacterium that would wreak havoc on Europe, the Middle East and northern Africa until the early 1800s, the scientists report June 15 in Nature.
“The source location and time when this plague emerged was most likely in Central Asia in the first half of the 14th century,” Spyrou said in a June 14 news briefing.
Origins of the Black Death, or bubonic plague, have long been debated. What’s certain is that Y. pestis gets transmitted to humans by fleas that live on rodents. One current proposal holds that the plague bacterium originated in East Asia and was carried across the continent starting in the 1200s as the Mongol Empire expanded. That scenario was based on historical records, ancient and modern plague genetic evidence, and reports of a plague outbreak connected to the Mongol conquest of Baghdad in 1258.
But solid archaeological and genetic clues to the Black Death’s place and time of birth come from Central Asia, Spyrou says. Excavations at two cemeteries in northern Kyrgyzstan almost 140 years ago revealed tombstones indicating that many people buried there in 1338 and 1339 had died of an unknown epidemic. The cemeteries were used from the mid-1200s to the mid-1300s, but tombstone inscriptions indicated that deaths spiked in 1338 and 1339. Of 467 dated tombstones, 118 mark deaths in those two years.
Spyrou’s group was able to reconstruct the entire Y. pestis genome for two of three Central Asian individuals who died in 1338 or 1339 and whose teeth contained remnants of bacterial DNA. Comparisons with the genetic instructions of 203 modern Y. pestis samples and 47 Y. pestis samples dating from the 14th to 18th centuries pegged the Central Asian genomes as a single strain that was a direct ancestor of 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 ancient variant. The Y. pestis variant that killed Central Asians in 1338 and 1339 may thus have emerged locally, the investigators suggest.
Source: Science News
