In the 1300s, the Black Plague swept through Europe. To create a “family tree” of the plague, scientists conducted a genetic analysis of Yersinia pestis strains taken from 34 individuals who died in 10 different countries between 1300 and 1700.
The results suggest that over time, the bacteria Yersinia pestis mutated and diversified into multiple clades. All the clades found in the study were related to back to one ancestral strain. That suggests that the Black Plague entered Europe just once. And the oldest strain, the one that appeared to have been the others’ ancestor, was from remains found in a little Russian town named Laishevo.
Here’s where a caution must be added. Such analyses are always limited by the available bacteria strains – the family tree will be added to over time as more bodies are recovered and more bacteria strains isolated.
