1665 Great Plague bacterium DNA identified for the first time

MOLA team

In the teeth of five skeletons, scientists have recovered DNA of the bacterium responsible for the 1665 Great Plague for the first time. The skeletons were found in a mass grave that we excavated for Crossrail's new Elizabeth line station at Liverpool Street in London. The 1665 outbreak was the last major bubonic plague outbreak in Britain but claimed almost a quarter of the population; an estimated 100,000 Londoners.

Our osteologists took samples from the teeth of 20 individuals from a mass burial discovered last summer in the New Churchyard. These were sent for testing at the Max Planck Institute in Germany, where they scanned for and later identified the plague pathogen, Yersinia pestis in five of the 20 samples. The enamel shells of the teeth protected and preserved the DNA, essentially acting as little time capsules, providing scientific evidence that these people had been exposed to the bacterium.

Other archaeological evidence, including pottery and coffin handles, point to the pit being in use in the mid-17th century, providing further evidence that it dates to the Great Plague.

Burial registers indicate that the New Churchyard had a dramatic increase in burials over the summer of 1665. In total 42 individuals were excavated from the mass grave but our archaeologists estimate that it may have contained as many as 100 people. The predominantly coffined burials were tightly packed in orderly rows that, over the centuries, collapsed in on each other as the coffins decayed. Although contemporary Plague Orders dictated that burials sit a minimum of 6ft from the surface, the top of the mass burial was only about 2ft from the surface. This was perhaps a matter of practicality for the gravediggers but ‘noisome stenches’ were reported, eventually leading to burial restrictions being placed on the New Churchyard.

Despite the Great Plague killing on such a devastating scale, traces of it have eluded archaeologists for some time – because it was such a fast-acting disease it left no trace on the bones. The fact that not all of the samples tested positive does not mean that these people did not die from the plague as the survival of ancient DNA is low when buried for hundreds of years.

Further scientific analysis of the skeletons is continuing over the coming months. Isotopic analysis may reveal where these people grew up and if they moved in their lifetimes, and examination of the material trapped within the plaque on the teeth may show what they ate, and what diseases and pollutants they were exposed to. These exciting findings provide a window into London’s tumultuous past and exciting new avenues for archaeological and medical research.

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