The debate about the origins of the medieval Black Death pandemic (AD 1346–1353) has focused on evidence from cemeteries in the Chüy Valley near Lake Issyk-Kul in modern-day Kyrgyzstan. These sites are thought to have victims of a 14th-century epidemic because of the tombstone dated 1338–1339 that attributes deaths to ‘pestilence’.  In a new study, an international team of researchers reports that they have identified DNA from the plague bacterium, Yersinia pestis, in 7 individuals who died in the year 1338 and had these inscriptions on their tombstones in two of these cemeteries.

“We could finally show that the epidemic mentioned on the tombstones was indeed caused by plague”, says Phil Slavin, one of the senior authors of the study and historian at the University of Sterling, UK.

It has been hypothesized that the Black Death’s initiation was associated with a massive diversification of plague strains, a so-called Big Bang event of plague diversity that may have happened sometime between the 10th and 14th centuries. Until now, this has not been verified. The authors of this new study pieced together complete ancient plague genomes from the sites in Kyrgyzstan and investigated how they might relate to this Big Bang event.

“We found that the ancient strains from Kyrgyzstan are positioned exactly at the node of this massive diversification event. In other words, we found the Black Death’s source strain and we even know its exact date [meaning the year 1338]”, says Maria Spyrou, lead author and researcher at the University of Tübingen.

They also tried to determine if the strains evolved locally or spread in this region from elsewhere. Plague is not a disease of humans; the bacterium survives within wild rodent populations across the world, in so-called plague reservoirs. Hence, the ancient Central Asian strain that caused the 1338-1339 epidemic around Lake Issyk Kul must have come from one such reservoir.

“We found that modern strains most closely related to the ancient strain are today found in plague reservoirs around the Tian Shan mountains, so very close to where the ancient strain was found. This points to an origin of Black Death’s ancestor in Central Asia”, explains Johannes Krause, senior author of the study and director at the Max Planck Institute for Evolutionary Anthropology.

The study demonstrates how investigations of well-defined archaeological contexts and close collaborations among historians, archaeologists, and geneticists can solve mysteries from our past.

The full article may be read here.