Scientists have used genetic data extracted from 700-year-old DNA to solve one of the great mysteries of medical history: the origins of the Black Death, which killed up to half of Europe’s population in the 14th century.

An international team of researchers now believes that the continent’s worst recorded pandemic began in Kyrgyzstan, after analysing the ancient DNA taken from human remains in two cemeteries where the surge of burials in 1338 and 1339 indicated a deadly epidemic. Some tombs near Lake Issyk-Kul are inscribed with the word “pestilence” in the Turkic language.

As well as human genes, the scientists found DNA from the bacteria that cause plague. They believe the Yersinia pestis infection had been transmitted by fleas from marmots, a type of ground squirrel, to the local trading communities.