Researchers have found the earliest known occurrence in Britain of Yersinia pestis, the bacteria that causes bubonic and pneumonic plague.
The bacteria has been spotted in three 4,000-year-old corpses, from two different burial sites.
Yersinia pestis is thought to be behind many of the most devastating disease outbreaks in recorded history, including the 14th-century Black Death and the 6th-century Justinianic plague.
Yersinia pestis has also been implicated in plagues that happened long before these two, including the Late Neolithic and Bronze Age (LNBA) plague.
In this study, researchers extracted ancient DNA from the teeth of 34 skeletons found at two British Bronze Age burial sites: a mass burial in Charterhouse Warren, Somerset, and a burial site in Levens Park, Cumbria. Both sites are roughly 4,000 years old.
Three of the individuals – two from Charterhouse Warren and one from Levens Park – had Yersinia pestis DNA present, and the researchers sequenced the genomes for all three.
All three of the genomes matched those of Yersinia pestis bacteria previously found in both older and newer Bronze Age samples from Central Europe all the way to Eastern Asia.
The genomes lack a gene called ymt, which is known to have made the plague more transmissible in fleas.
Prior to this research, the westernmost evidence of Yersinia pestis without the ymt gene was in present-day Germany, in a 3,400-year-old individual.
The presence of the lineage in Britain means that this variant of the plague was widespread and likely quite transmissible.
It’s still unclear how severe it was. Charterhouse Warren is an unusual mass burial site, but many of the individuals buried there show evidence of fatal trauma, meaning it’s unlikely that they died of plague.
While the researchers couldn’t find evidence of Yersinia pestis in the other individuals buried at the site, they could be false negatives: DNA frequently degrades over time.
“This raises the question–which we cannot answer at this point–of whether there may have been any connection between the disease and violent treatment of these individuals,” write the researchers in their paper.
Either way, the second site at Levens Park is a much more ordinary burial for the period.
“Further high-resolution sampling will be needed to answer these questions and better understand the transmission dynamics and functional evolution of Yersinia pestis in Britain and beyond,” write the researchers.
The research, done by researchers based at the Francis Crick Institute, UK, is published in Nature Communications.