Tooth enamel of Bedlam burial ground bodies finds first DNA of the bacteria behind the Great Plague

By Ben Miller | 08 September 2016

Archaeologists suspected a mass gave within the Bedlam burial ground, where 42 individuals were found last summer, contained victims of Britain’s last bubonic plague. Now five of the 20 individuals tested in Germany have shown traces of the plague pathogen, Yersinia pestis, as Michael Henderson, a Senior Human Osteologist at Museum of London Archaeology, explains

A photo of an osteologist looking at a skeleton at the bedlam great plague burial ground
A mass grave containing 42 individuals, suspected of being victims of the Great Plague of 1665, was discovered within the Bedlam Burial Ground in London in August 2015© Crossrail
“The Great Plague was responsible for the deaths of 100,000 – nearly a quarter of London’s population. We know that the churchyard was used for plague burials – people like Defoe described mass burial pits with people thrown in haphazardly and naked.

The evidence from the churchyard suggests that people were actually placed in coffins in orderly rows utilising all the available space. A degree of care and attention was given to them.

The pit was half a metre below the surface. This goes against what we know from rules that were imposed at the time. They stipulated that burials had to be at least six foot below the ground, so this really shows that people were utilising all available space to bury these dead.

A photo of an osteologist looking at a skeleton at the bedlam great plague burial ground
The excavation of the 17th century ground revealed more than 3,300 burials in March 2015© Crossrail
But at the same time, at a time of mass mortality and high, high deaths, a degree of respect and dignity was still given to the dead.

One of the problems we have as osteologists is that a lot of the diseases that people died from in the past, things like smallpox and influenza and plague, kill you so quickly that you don’t see marks on the skeletons. So we have to look for other means to be able to conclusively say if people had indeed died of these diseases.

We were fortunate enough to be involved in a lot of other scientific testing. Ancient DNA is very vulnerable to contamination and suffers from poor preservation, so we laid out the skeletons under controlled conditions and we took samples of a tooth from each individual. This is because teeth are like sealed capsules that preserve this information better than other parts of the skeleton.

A photo of an osteologist looking at a skeleton at the bedlam great plague burial ground
MOLA senior archaeologist Don Walker Henderson examining one of the victims© Crossrail
This was sent to the Max Planck Institute for analysis. The really exciting news was that these five individuals had positive evidence of the senior pestis plague bacterium.

They were exposed to the disease. This is the first time that the ancient DNA of the 1665 Great Plague has been found in this country.

The DNA testing was only part of an array of scientific tests. Following this, we’re going to be looking to sequence the full genome of the ancient DNA pathogen.

A photo of an osteologist looking at a skeleton at the bedlam great plague burial ground
The DNA was isolated from extracted teeth at the Max Planck Institute in Jena, Germany© Crossrail
This will enable us to see the full evolution of the disease. How does it compare to previous outbreaks such as the medieval black death? How did it enter Europe and Britain? How did it affect people and what people were likely to succumb to the disease?

Other scientific tests including stable isotopes will tell us about where people were born and where they migrated from, possibly what they ate and the components of their diet. Analysis of the dental calculus might contain food particles, pollutants and air particles.

From the detailed analysis of the skeletons we’ve learnt a great amount about the individuals that lived and died and were buried in the burial ground. Bringing together all of this information with all the archaeological information will teach us a lot about these people.

All of this evidence, archaeological information and all of the stories we’ve learnt will be published in a book to be released in 2017.”

A photo of an osteologist looking at a skeleton at the bedlam great plague burial ground
Molecular palaeopathologists are now attempting to sequence the pathogen's full DNA genome© Crossrail

The tests

  • A total of 40 individuals from the New Churchyard were sampled for ancient DNA and other scientific testing. This comprised 20 samples from individuals buried in the mass burial pit and a further 20 from elsewhere in the burial ground, as a control sample. No evidence of plague was found in the control sample.

  • The samples were taken in controlled conditions by a team of osteologists from MOLA and then sent to the Max Planck Institute for the Science of Human History in Jena, Germany.

  • A greater proportion of sub-adults (0 to 17 years) were found in the mass burial pit when compared to the remainder of the burial ground. This is consistent with ‘catastrophic assemblages’ in which you are more likely to see a truer representation of the living population.

A photo of an osteologist looking at a skeleton at the bedlam great plague burial ground
Experts hope to compare the 1665 Great Plague to the 1348 Black Death epidemic, as well as recent modern outbreaks© Crossrail
  • In most instances the coffins had almost entirely decayed, although one coffin was recognisable as a flat-lidded ‘single break’ form, which became ubiquitous during the second half of the 17th Century. The absence of any soil between the burials in the pit could suggest that it was filled in a single event and not kept open for more than a short period.

  • The surviving section of the mass burial pit measured 2.3m by 2.3m and contained 42 burials. However, this section represents only the south end of the pit and no more than half of its original size. The remaining part of the pit had been disturbed by 19th and 20th Century development of the site. It can be estimated that the pit may well have originally contained at least 90 to 100 individuals.

  • Elsewhere on the site MOLA archaeologists uncovered a headstone, reused in a later wall, that belonged to a plague victim named Mary Godfrey. Mary’s burial is recorded in the burial register of St Giles, Cripplegate, on 2 September 1665.

  • The fact that not all of the skeletons tested from the pit came back with a positive result does not mean that they were not also exposed to or killed by the plague. When a body lies buried in the ground for hundreds of years the rate of survival of ancient DNA reduces considerably. The plague bacterium does not survive in the ground so there is no risk of releasing plague.

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Absolutely fascinating, well done, it's good that something so positive can cime from such misery.
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