The oldest evidence of the plague in Britain has been found in the teeth of human remains – dating the disease back 4,000 years.
Researchers from the Francis Crick Institute have identified the presence of Yersinia pestis, the bacteria that causes the plague, in three individuals. Two cases were found in an unusual mass burial in Charterhouse Warren, Somerset, and the third in a ring cairn monument in Levens, Cumbria.
Working with the University of Oxford, the Levens Local History Group and the Wells and Mendip Museum, the team took skeletal samples from 34 individuals across the two sites. Extracting dental pulp from the teeth, they analysed DNA remnants found inside and identified the presence of Yersinia pestis.
Two of those carrying the bacteria were children thought to be between 10 and 12 years old when they died, and the third a woman between 35 and 45. Radiocarbon dating suggests all lived around the same time, in the Late Neolithic and Bronze Age (LNBA).
While Yersinia pestis is the same bacteria that led to the Black Death in the 14th Century and the Great Plague of 1665-1666, the earlier strain identified is missing the ymt gene known to play an important role in transmission via fleas, a major vector during later outbreaks.
However, it appears to be very similar to a strain already identified in Eurasia around the same time, which was first seen in Central and Western Europe around 4,800 years ago.
And while two of the individuals were found in a mass burial site, the team suggests it was unlikely the grave was due to an outbreak of the plague – remains uncovered suggest they died of trauma.
‘The ability to detect ancient pathogens from degraded samples, from thousands of years ago, is incredible,’ said Pooja Swali, first author and PhD student at the Crick. ‘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.’
Pathogenic DNA – DNA from bacteria, protozoa or viruses which cause disease – degrades very quickly in incomplete samples, which means others at the two sites may have also been infected, but the evidence wasn’t preserved.
Pontus Skoglund, group leader of the Ancient Genomics Laboratory at the Crick, added: ‘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.
‘We understand the huge impact of many historical plague outbreaks, such as the Black Death, on human societies and health, but ancient DNA can document infectious disease much further into the past.
‘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 study is published in Nature Communications.
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