Three cases of Yersinia pestis, the bacterium that causes plague, have been identified in human remains. Two of these were found in a mass grave in Somerset and the third in a public memorial in Cumbria.

To investigate the presence of Yersinia pestis in the teeth, a team of scientists took small samples from the skeletons of 34 people. Dental pulp has been studied for storing the DNA of infectious diseases.

Scientists from the Francis Crick Institute collaborated with the University of Oxford, the Levens Local History Group, and the Wells and Mendip Museum to make the discovery.

Pooja Swali, Crick’s first author and postdoctoral researcher, said: “The ability to detect ancient pathogens in degraded samples that have existed for thousands of years is incredible. These genomes can help us understand the distribution and evolutionary changes of pathogens in the past, as well as identify genes that play an important role in the spread of infectious diseases.” We observe that this strain of Yersinia pestis, including the genomes in this study, loses its genes over time, which is a feature of later outbreaks caused by the same pathogen.”

The researchers also did DNA analysis and found three cases of Yersinia pestis—two children aged 10 to 12 when they died, and a woman aged 35 to 45.

According to the researchers’ conclusions, these three people probably lived at about the same time.

The scientists say that this type of plague discovered in the study belongs to the late Neolithic and Bronze Age. It was probably brought to Central and Western Europe by people entering Eurasia around 4800 BC. This study also shows that this strain of plague has spread as far as England.