Plagues have been a part of human history for thousands of years, wreaking havoc on populations at various points in time. The study of ancient plague DNA can shed light on the history and evolution of these diseases.
Three 4,000-year-old British cases of Yersinia pestis, the bacteria that causes the plague, have been identified by researchers as the oldest evidence of the plague in Britain to date. The Francis Crick Institute has discovered three 4,000-year-old British cases of Yersinia pestis, the bacteria that causes the plague – the oldest evidence of the plague in Britain to date, according to a paper published today in Nature Communications.
The team identified two cases of Yersinia pestis in human remains found in a mass burial in Charterhouse Warren, Somerset, and one in a ring cairn monument in Levens, Cumbria, in collaboration with the University of Oxford, the Levens Local History Group, and the Wells and Mendip Museum.
They collected small skeletal samples from 34 people across two sites to test for the presence of Yersinia pestis in teeth. This technique is carried out in a specialized clean room facility, where they drill into the tooth and extract dental pulp, which can trap infectious disease DNA remnants.
The ability to detect ancient pathogens from degraded samples from thousands of years ago is incredible. These genomes can help us understand the spread and evolution of pathogens in the past, as well as which genes may be important in the spread of infectious diseases.
Pooja Swali
They then analyzed the DNA and discovered three cases of Yersinia pestis in two children aged 10 to 12 years old when they died, and one woman aged 35 to 45. Radiocarbon dating was used to determine that the three people most likely lived at the same time.
The plague had previously been identified in several individuals from Eurasia between 5,000 and 2,500 years before the present (BP), a time span spanning the Late Neolithic and Bronze Age (termed LNBA), but had never been seen in Britain before. The wide geographic spread of this strain of the plague suggests that it was easily transmitted.
This strain of the plague – the LNBA lineage – was likely brought into Central and Western Europe around 4,800 BP by humans expanding into Eurasia, and now this research suggests that it extended to Britain. Using genome sequencing, the researchers showed that this strain of Yersinia pestis looks very similar to the strain identified in Eurasia at the same time.
The individuals identified all lacked the yapC and ymt genes, which are found in later strains of plague, the latter of which is known to play an important role in plague transmission via fleas. This information has previously suggested that, unlike later plague strains such as the one that caused the Black Death, this strain of the plague was not transmitted by fleas.
Because pathogenic DNA (DNA from bacteria, protozoa, or viruses that cause disease) degrades quickly in incomplete or eroded samples, it’s possible that other people at these burial sites were infected with the same strain of plague.
The Charterhouse Warren site is rare as it doesn’t match other funeral sites from the time period — the individuals buried there appear to have died from trauma. The researchers speculate that the mass burial wasn’t due to an outbreak of plague but individuals may have been infected at the time they died.
“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 help us understand the spread and evolution of pathogens in the past, as well as which genes may be important in the spread of infectious diseases. We see that this Yersinia pestis lineage, including the genomes used in this study, loses genes over time, a pattern that has been observed in subsequent epidemics caused by the same pathogen.”
“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,” said Pontus Skoglund, group leader of the Crick’s Ancient Genomics Laboratory.Many historical plague outbreaks, such as the Black Death, had a huge impact on human societies and health, but ancient DNA can document infectious disease much further back in time. Future research will focus on how our genomes responded to such diseases in the past, as well as the evolutionary arms race with pathogens, which can help us understand the impact of diseases now and in the future.”
