DNA tests have helped scientists confirm exactly what caused the Great Plague which swept through London in 1665.

The outbreak is thought to have killed 100,000 people – which was almost a quarter of the capital’s total population at the time. And now researchers have proved that the deaths were as a result of plague caused by the bacterium Yersinia pestis, which was also responsible for the Black Death, which wiped out around 1.5 million people in England between 1348 and 1350.

DNA samples were collected from teeth belonging to 20 skeletons which were discovered by builders working on a new Crossrail station at London’s Liverpool Street. The remains had been laid to rest in a mass burial ground and they were exhumed so they could be studied.

Tests showed that a significant number of the samples taken from the skeletons tested positive for yersina pestis. This ends doubts and questions historians have had about exactly what caused the deadly epidemic in the 17th century.

Findings end doubts over cause of outbreak

Don Walker, who works at the Museum of London Archaeology as a senior human osteologist, told the Independent: “It’s significant because we had this famous, severe outbreak of plague in 1665, but until very recently, there was quite a lot of doubt about what had caused it. Four or five years back, [scientists] studied some skeletons from the Black Death, which was the first outbreak of plague in Britain.

“They identified what had caused the black death in the middle of the 14th century was yersina pestis, the plague bacterium, but they weren’t sure what caused later outbreaks of the plague. It appears now that it was the same bacterium that lasted throughout those centuries.”

DNA has proved effective at solving a number of mysteries since its discovery. While DNA tests can be used to provide answers to historical questions, they are more commonly used to resolve much more recent issues.

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