Europeans must have thought it was the end of the world. War was spreading across the continent, there was famine after flooding made crops rot in the fields, and an incurable plague was wiping out entire settlements. The Black Death is considered to have been the deadliest pandemic in history. Starting in 1347 and lasting five years, the plague killed 30-50% of the population of western Europe. In London, people were dying so fast the town had to establish two new cemeteries outside the city walls. At its height, 200 bodies a day were being sent to the burial sites in East Smithfield, not far from the Tower of London, to be stacked up.
Now, by examining remains from some London cemeteries, scientists have deciphered the genetic makeup of the bacterium that caused the pandemic and have discovered that its DNA is not very different from that of the modern bug that causes bubonic plague.
“We have covered about 99% of the ancient Yersinia pestis [the bacterium that caused the disease] genome,” said Johannes Krause, of the University of Tübingen, in Baden-Württemberg, Germany, and also leader of the research team. “When we compare this reconstructed genome with modern strains of Yersinia pestis … we do not see a single position in this ancient genome which cannot be found in modern strains.”