They studied the skeletons’ teeth, because enamel acts as a kind of time capsule in preserving the genetic information of any bacteria that was circulating in the individual’s bloodstream at the time of death.
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Scientists have recovered DNA from the bacterium that caused London’s 1665 Great Plague by studying the teeth of five skeletons. “Other archaeological evidence, including pottery and coffin handles, point to the pit being in use in the mid-17th century, providing further evidence that it dates to the Great Plague”. But don’t worry, the bacteria would have died just days after the people did, so researchers won’t be unleashing any new plagues by digging up the site.
The samples were sent for analysis at Germany’s Max Planck Institute and the plague pathogen Yersinia pestis was found in five of the 20 samples. Despite killing approximately 100,000 people – almost a quarter of the city’s population – archeologists have struggled to find hard-and-fast traces of it in skeletal remains due to the fast-acting nature of the disease, which leaves afflicted bones with no DNA evidence.
The researchers believe these DNA investigations can also help us understand today’s plague epidemic, which continues to infect hundreds each year, mainly in Africa.
Molecular palaeopathologists are now attempting to sequence the pathogen’s full DNA genome.
Don Walker, Senior Human Osteologist at the Museum of London Archaeology, said that the discovery is significant because the causative agent behind the outbreak is unclear. It confirms thatYersinia pestis was present in early modern London plague epidemics, and links them epidemiologically with the 14th-Century Black Death and the 1720 Marseille plague.
Other than piecing together history, it’s good to know more about diseases like the plague to understand how it spreads, evolves and is similar to today’s diseases.
Excavators found about 3,500 burials at the site.
In total 42 individuals were excavated from the mass grave but archaeologists estimate that it may have contained as many as 100 people. Isotopic analysis may reveal where these people grew up and if they moved in their lifetimes, and examination of the material trapped within the plaque on the teeth may show what they ate, and what diseases and pollutants they were exposed to.
“To dig below London is frequently to travel back in time”, The Guardian reported past year.
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The identification also marks the 350th anniversary of the Great Fire of London that swept through the city in 1966 – another vital piece of the puzzle that many accredit to wiping out the plague once and for all.
