Although bubonic plague has been suspected to be much older, until recently the Justinian Plague of the 6th Century was the earliest confirmed instance of Yersinia pestis, the bacterium that causes plague. That has now changed. The New York Times reports:
[I]n a new study, published on Thursday in the journal Cell, researchers report that the bacterium was infecting people as long as 5,000 years ago.
Exactly what those early outbreaks were like is impossible to know. But the authors of the new study suggest that plague epidemics in the Bronze Age may have opened the doors to waves of migrants in regions decimated by disease.
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The new study arose from previous research by Dr. Willerslev and his colleagues. They were able to extract human DNA from 101 bones found in Europe and Asia, ranging in age from about 3,000 to 5,000 years old.
As they reported in June, the genetic profiles of people during that 2,000-year period changed with surprising abruptness. About 4,500 years ago, for example, the DNA of Europe’s inhabitants suddenly took on a strong resemblance to that of the Yamnaya, a nomadic people from western Russia.
Wondering what could have triggered such a shift, Dr. Willerslev and his colleagues realized they could test one hypothesis: that epidemics had decimated some populations, allowing new groups to establish themselves.
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Dr. Willerslev and his colleagues wondered if some of the nonhuman DNA they had collected from Bronze Age remains might belong to pathogens. They decided to look for traces of Yersinia pestis, even though the earliest evidence of the infection dates to thousands of years later.
“Plague was just a long shot,” said Dr. Willerslev.
But sometimes long shots pay off. Of 101 Bronze Age individuals, the researchers found Yersinia pestis DNA in seven. Plague DNA was present in teeth recovered from sites stretching from Poland to Siberia.Related Posts: "Book Review--Plague by Wendy Orent"
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