The Black Death began in 1338 in what is now Kyrgyzstan, new research suggests.
The bubonic plague outbreak ravaged the world between 1346 and 1353 and is the most deadly pandemic recorded in human history, causing the deaths of up to 200 million people.
Bubonic plague is caused by the bacterium Yersinia pestis and is spread by fleas, but it can also take a secondary form where it is spread from person to person via droplets in the air.
In 1347, it first entered the Mediterranean via ships transporting goods from the territories of the Golden Horde in the Black Sea.
The deadly disease then spread across Europe, the Middle East and northern Africa claiming up to 60 per cent of the population in a large-scale outbreak which earned it the nickname the Black Death.
The first wave further extended into a 500-year-long pandemic, known as the second plague pandemic, which lasted until the early 19th century.
The origins of the second plague pandemic have been the subject of debate. One of the most popular theories has supported its source in east Asia, specifically in China.
However, the only available archaeological findings so far have come from central Asia, close to Lake Issyk Kul, in what is now Kyrgyzstan.
The findings show that an epidemic devastated a local trading community in the years 1338 and 1339.
Excavations that took place almost 140 years ago revealed tombstones indicating that people died in those years of an unknown epidemic or “pestilence”.
Since they were first discovered, the tombstones – inscribed in the Syriac language – have been a cornerstone of controversy among scholars regarding their relevance to the Black Death in Europe.
For the study, an international team of researchers analysed ancient DNA from human remains as well as historical and archaeological items from two sites that were found to contain “pestilence” inscriptions.
The team’s first results were very encouraging, as DNA from the plague bacterium, Y. pestis, was identified in individuals with the year 1338 inscribed on their tombstones.
Study senior author Doctor Phil Slavin, an associate professor in history at the University of Stirling in Scotland, said: “We could finally show that the epidemic mentioned on the tombstones was indeed caused by the plague.”
Researchers have previously associated the Black Death’s initiation with a massive diversification of plague strains, a so-called Big Bang 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.
The research team has now pieced together a complete ancient plague genome from the Kyrgyzstan sites and investigated how they might relate with the “Big Bang” event.
Lead author Dr Maria Spyrou, of the University of Tübingen, Germany, said: “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.”
She explained that plague is not a disease of humans; the bacterium survives within wild rodent populations around the world, in so-called plague reservoirs.
The ancient central Asian strain that caused the 1338-39 epidemic around Lake Issyk Kul must have come from one such reservoir, say the researchers.
Co-senior author Prof Johannes Krause added: “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.”
Prof Krause, director of the Max Planck Institute for Evolutionary Anthropology in Germany, added: “This points to an origin of Black Death’s ancestor in central Asia.”
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