The germ that causes the plague began infecting humans thousands of years earlier than scientists had previously thought.

Researchers analyzed teeth from the remains of 101 individuals that were collected from a variety of museums and archaeological excavations. They found DNA of the bacterium that causes plague, called Yersinia pestis, in seven of these people. The earliest sample that had plague DNA was from Bronze Age Siberia, and dated back to 2794 B.C., and the latest specimen with plague, from early Iron Age Armenia, dated back to 951 B.C.

Previously, the oldest direct molecular evidence that this bacterium infected humans was only about 1,500 years old.

“We were able to find genuine Yersinia pestis DNA in our samples 3,000 years earlier than what had previously been shown,” said Simon Rasmussen, a lead author of the study and a bioinformatician at the Technical University of Denmark.

Read the article “Discovered: The Dreaded Black Plague Began Infecting Humans Earlier than Thought” on cbsnews.com.