Skeletons unveil secrets of the Black Death and whether it was spread by rats after all

ONE of the deadliest diseases ever recorded has had us running scared of rats ever since. But new findings reveal we might be wrong for blaming our furry foes.

You dirty little rat. Or maybe not. Skeletons unearth new findings about the Black Death including a challenge to the common theory it was spread by fleas from rats.

You can learn a lot from a tooth.

Molars taken from skeletons unearthed by work on a new London railway line are revealing secrets of the medieval Black Death — and of its victims.

Twenty five skeletons were uncovered last year during work on Crossrail, a new rail line that’s boring 21 kilometres of tunnels under the heart of London. Archaeologists immediately suspected the bones came from a cemetery for plague victims. The location, outside the walls of the medieval city, chimes with historical accounts. The square, once home to a monastery, is one of the few spots in the city to stay undisturbed for centuries.

To test their theory, scientists took one tooth from each of 12 skeletons, then extracted DNA from the teeth. They announced Sunday that tests had found the presence of the plague bacterium, Yersinia pestis, in several of the teeth, meaning the individuals had been exposed to — and likely died from — the Black Death.

News_Image_File: A human osteologist with one of the skeletons found by construction workers under central London's Twenty-five skeletons were uncovered and their teeth have been studied to reveal some interesting findings.

The findings didn’t stop there. Archaeologists, historians, microbiologists and physicists worked together to apply techniques from several scientific disciplines to the discovery.

Radiocarbon dating and analysis of pottery shards helped determine when the burials took place. Forensic geophysics — more commonly used in murder and war-crimes investigations — helped locate more graves under the square. Studying oxygen and strontium isotopes in the bones revealed details of diet and health.

These were, by and large, poor people. Many of the skeletons showed signs of malnutrition consistent with the “Great Famine” that struck Europe 30 years before the Black Death. Many had back injuries suggesting lives of hard labour.

Archaeologists were surprised to discover that the skeletons lay in layers and appeared to come from three different periods: the original Black Death epidemic in 1348-1350, and later outbreaks in 1361 and the early 15th century.

News_Rich_Media: Though we think of the Plague as something that happened centuries ago, it is still an ongoing concern.

“It suggests that the burial ground was used again and again for the burial of plague victims,” said Jay Carver, Crossrail’s lead archaeologist.

The Black Death is thought to have killed at least 75 million people, including more than half of Britain’s population, yet the burials suggest a surprisingly high degree of social order — at first. As the plague ravaged continental Europe city fathers leased land for an emergency burial ground. The burials were simple but orderly, the bodies wrapped in shrouds and laid out in neat rows, sealed with a layer of clay.

The later skeletons, however, show more signs of upper-body injuries, consistent with a period of lawlessness and social breakdown.

But social order is the tip of the iceberg. Through examining the teeth it has questioned the one fact many hold accountable for the mass infection: that it was spread by fleas from rats.

Evidence suggests this might not be the case due to how quickly it was spread. Scientists have compared a strain of bubonic plague that killed 60 people in Madagascar last year with that from the 14th-century and noted it was no more virulent than today’s disease.

It is suggested that any plague to spread at such a pace it must have been spread by victims coughing and sneezing — making it a pneumonic plague rather than a bubonic plague. Therefore it was the human-to-human contagion rather than fleas from rats biting humans and spreading the disease.

“As an explanation [rat fleas] for the Black Death in its own right, it simply isn’t good enough. It cannot spread fast enough from one household to the next to cause the huge number of cases that we saw during the Black Death epidemics,” said Dr Tim Brooks from Public Health England.