Plague DNA has been found dating back 4,000 years, making it the oldest evidence of the disease in Britain.
The discovery by researchers could help to understand which genes are “important in the spread of infectious diseases”, one of them said.
Scientists from the Francis Crick Institute (FCI) have identified three cases of Yersinia pestis – the bacteria that causes plague – in human remains.
Two were discovered at a mass burial at Charterhouse Warren in Somerset, and the other one in a ring cairn monument in Levens, Cumbria.
Working with local groups and the University of Oxford, the team took small skeletal samples from 34 individuals across the two sites.
They then drilled into teeth and extracted dental pulp, which can trap DNA remnants of infectious diseases.
Author Pooja Swali, a PhD student at the FCI, said that being able to detect “ancient pathogens from degraded samples” from such a long time ago was “incredible”.
She added: “These genomes can inform us of the spread and evolutionary changes of pathogens in the past, and hopefully help us understand which genes may be important in the spread of infectious diseases.
“We see that this Yersinia pestis lineage, including genomes from this study, loses genes over time, a pattern that has emerged with later epidemics caused by the same pathogen.”
Previously, plague has been identified in several individuals from Eurasia between 5,000 and 2,500 years before present (BP).
It has not been seen before in Britain during that period, the researchers suggested.
It is thought its widespread geographical spread suggests it was easily transmitted.
Pontus Skoglund, group leader of the Ancient Genomics Laboratory at the FCI, said: “This research is a new piece of the puzzle in our understanding of the ancient genomic record of pathogens and humans, and how we co-evolved.
“Future research will do more to understand how our genomes responded to such diseases in the past, and the evolutionary arms race with the pathogens themselves, which can help us to understand the impact of diseases in the present or in the future.”
The findings are published in Nature Communications.