A team of researchers excavating mass burial sites in England has detected the DNA of the bacteria that caused the plague in human skeletal remains – and they are the oldest known cases of the disease in Britain.
The cases of Yersinia pestis date back 4,000 years, according to the article published on Tuesday (30) in the journal Nature Communications.
Bacterial DNA is thousands of years older than the oldest discovered strain. That strain, identified in 2018 in a cemetery known as Edix Hill in Cambridgeshire, dated back 1,500 years, according to the study’s lead author, Pooja Swali, a doctoral student at the Skoglund Laboratory at the Francis Crick Institute in London.
Samples of the plague-causing bacteria were found in two different cemeteries: one in southwest England, in Somerset County, and the other in northwest Cumbria, near England’s border with Scotland.
The distance between the sites suggests the disease spread during the late Neolithic and Bronze Age, Swali said.
“The evidence for widespread transmission over such a vast space area in just a few centuries is very interesting and appears to be one aspect of the rapid movement of people, technologies and ideas during this period,” said Dr. Benjamin Roberts, an associate professor of archeology who researches European prehistory at Durham University in the United Kingdom. He was not involved in the study.
The team collected samples from the remains of 34 individuals at the two sites, according to the study. The researchers drilled into the teeth of these ancient peoples and extracted the dental pulp, which can trap remnants of infectious disease DNA.
“The ability to detect ancient pathogens from degraded samples from thousands of years ago is amazing,” said Swali. “These genomes can inform us about the spread and evolutionary changes of pathogens in the past, and hopefully help us understand which genes might be important in the spread of infectious diseases.”
What We Learned About Transmission
Using genetic analysis, the researchers determined that there were two distinct periods when the plague appeared in Britain: the disease broke out before or around 4,000 years ago and again around 1,500 years ago, said Dr. Lee Mordechai, a senior professor of history at the Hebrew University of Jerusalem, who was not involved in the study.
When it comes to the disease, there’s a lot scientists still don’t know, including how it spread, Swali said.
The strain of Yersinia pestis found in cemeteries did not contain the gene that would allow it to spread through fleas, a trait possessed by the strain that caused the pandemic known as the Black Death that later devastated medieval Europe in the 14th century, she added.
And science may never truly know how serious the plague of 4,000 years ago was when it came to humans, Roberts said.
The researchers cannot say whether the illness caused by the bacteria would have been mild or fatal, he added. And individuals at the Somerset site appeared to have died from trauma, not disease, according to the research.
“The temptation is always to theorize a medieval Black Death doomsday scenario, but we simply cannot justify that with the evidence we have,” Roberts said via email.
Ancient DNA in modern times
The research presents lessons for today. The findings demonstrate the importance of scholars working together across disciplines, as archaeologists and paleogeneticists have done in this work, Mordechai said.
The report also shows that large-scale disease transmission dates back to prehistoric times, he added.
“More recent pandemics like Covid, AIDS or Spanish flu are recent cases of a recurring phenomenon,” Mordechai said via email.
And while there are historical records of plague outbreaks, ancient DNA could potentially give us even more distant insight, Swali said.
“Future research will do more to understand how our genomes have responded to these diseases in the past and the evolutionary arms race with the pathogens themselves, which may help us understand the impact of diseases in the present or the future,” she said.
Source: CNN Brasil
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