From Science News, courtesy my friend William Campbell:
A 5,000-year-old mass grave harbors the oldest plague bacteria ever found
A long-dead Scandinavian woman has yielded bacterial DNA showing that she contracted the earliest known case of the plague in humans.
DNA extracted from the woman’s teeth comes from a newly identified ancient strain of Yersinia pestis, the bacterium that causes plague, the oldest ever found. The woman’s bones, which date from 5,040 to 4,867 years ago, were found nearly 20 years ago in a mass grave at an ancient farming site in Sweden.
Teeth from an adult male in the same grave contain traces of the same plague variant, say evolutionary geneticist Simon Rasmussen of the University of Copenhagen and colleagues. But plague DNA from the woman is better preserved, the team reports online December 6 in Cell.
Comparisons of the newly found Y. pestis strain with other ancient and modern strains suggest that a plague epidemic emerged more than 5,000 years ago in densely populated farming communities in southeastern Europe. Then the plague spread elsewhere, including to Scandinavia, via trade routes, Rasmussen’s team concludes. That ancient epidemic apparently contributed to sharp population declines in Europe that began as early as 8,000 years ago.
In particular, the scientists suspect that an early form of plague developed among southeastern Europe’s Trypillia culture between 6,100 and 5,400 years ago. Trypillia settlements were the first to bring enough people into close contact to enable the evolution of a highly infectious version of Y. pestis, the team suggests. Trading networks then transmitted the plague from Trypillia population centers, home to as many as 10,000 to 20,000 people, to West Asian herders known as the Yamnaya, the researchers argue. In this scenario, herders infected by the Trypillia people probably spread what had become a new strain of the plague both eastward to Siberia and westward to the rest of Europe, including Scandinavia. Yamnaya migrations to Europe roughly coincided with the rapid abandonment and burning of large Trypillia settlements, which probably occurred as a result of plague outbreaks, the scientists say.
More at the link.