London: Researchers believe to have identified the origins of Black Death, a bubonic plague that killed tens of millions in Europe, Asia and north Africa during the mid-14th century.
In 1347, plague first entered the Mediterranean via trade ships transporting goods from the territories of the Golden Horde in the Black Sea. The disease then disseminated across Europe, the Middle East and northern Africa claiming up to 60 per cent of the population in a large-scale outbreak known as the Black Death.
This first wave further extended into a 500-year-long pandemic, the so-called Second Plague Pandemic, which lasted until the early 19th century.
The origins of the Second Plague Pandemic have long been debated. One of the most popular theories has supported its source in East Asia, specifically in China.
To the contrary, the only so-far available archaeological findings come from Central Asia, close to Lake Issyk Kul, in what is now Kyrgyzstan.
In the new study, an international team of researchers analysed ancient DNA from human remains as well as historical and archaeological data from two sites that were found to contain “pestilence” inscriptions.
The team’s first results were very encouraging, as DNA from the plague bacterium, Yersinia pestis, was identified in individuals with the year 1338 inscribed on their tombstones.
“We could finally show that the epidemic mentioned on the tombstones was indeed caused by plague,” said Phil Slavin, historian at the University of Sterling, UK.
Researchers have previously associated the Black Death’s initiation with a massive diversification of plague strains, a so-called Big Bang event of plague diversity. But the exact date of this event could not be precisely estimated, and was thought to have happened sometime between the 10th and 14th centuries.
In the study, published in the journal Nature, the team pieced together complete ancient plague genomes from the sites in Kyrgyzstan and investigated how they might relate with 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),”, said Maria Spyrou, lead author and researcher at the University of Tubingen.
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.