Records showed that during the bubonic plague outbreak, thousands of plague victims were buried in a mass grave, but no one knew where that mass grave was located. The combination of multiple remains and artifacts led people to believe the Crossrail dig may be the beginning to the solution of a mystery well over 600 years old.
Samples from nearly half of the skeletal remains were removed for forensic analysis. In four of the ancient corpses, teeth were confirmed to contain trace amounts of DNA from Yersinia pestis (the bacterium of the plague), thus confirming that the victims had contact with the plague prior to their death.
Radio carbon dating was used to try to pinpoint which particular outbreak claimed the victims, know colloquially known as the "Charterhouse 25" for the area they were found in near Charterhouse Square. The results indicated that victims came from two separate outbreaks-one in the original wave of the Black Death in Britain from 1348-1350 and another outbreak in the 1430's.
On the assumptions that the uncovered bodies are part of a much larger mass gravesite, ground-penetrating radar was brought in to try to determine how far across Charterhouse Square the burial site might extend. The initial results did show some evidence of further burials, but more excavations will be necessary to verify the results.
Meanwhile, the discovery of the bodies gave scientists a treasure trove of well-preserved 660-year old information. Further analysis of the teeth and bones at the site yielded interesting, yet bleak, information about the victims and their lives.
Among the facts discovered: 16% of the skeletons were found to have rickets, and the vast majority showed signs of malnutrition. Significant back damage was found, indicating a large amount of heavy manual labor. The skeletons from the 1400s were engaged in some violent activities based on the prevalence of upper body injuries.
The lives of these victims were likely hard enough before the Black Death arrived-in fact, that hard life might have increased their susceptibility to the plague that would eventually kill them.
Why would we want to study this in greater detail? Because the plague exists today-some 2,000 people die from the plague every year, even though antibiotics can successfully treat the plague these days. (Unfortunately, lack of treatment makes the plague fatal after four days).
Through sequencing of the 660-year old bacterial DNA, researchers hope to discover more insights into the evolution and spread of the plague, and whether the plague as we know it today is truly descended from the ancient plague. Potentially, this could lead to better understanding of how the plague and similar bacteria affect humans and, in turn, perhaps head off future pandemics.