(NYT) – The oldest known cases, discovered among hunter-gatherers in Siberian graves, contradict the theory that the disease once was mild.

In ancient Siberian graves, scientists have discovered the oldest traces of one of humanity’s greatest enemies. Examining skeletons of hunter-gatherers who lived 5,500 years ago, the researchers have isolated DNA from the bacteria that cause the plague.

The findings suggest that the plague, which would later devastate Europe in the “Black Death,” was already a lethal threat early in human history. That would be a big change from the earlier view of scientists: that these bacteria were originally relatively mild, and only later produced deadly outbreaks. (Read More)