For the first time, scientists have uncovered direct genomic evidence of the bacteria behind the Justinian Plague, the world’s first recorded pandemic, in the ancient city of Jerash, Jordan.

The discovery links Yersinia pestis to the outbreak that struck the Byzantine Empire between 541 and 750 AD, killing tens of millions and reshaping the course of Western civilization.

Researchers from the University of South Florida, Florida Atlantic University, and international partners analyzed ancient DNA from human teeth found in a mass grave beneath Jerash’s former Roman hippodrome. The results showed nearly identical strains of the plague bacterium among all victims, providing the first conclusive biological proof of the disease in the region.

“This finding offers the long-awaited evidence of Y. pestis at the heart of the Justinian Plague,” said lead researcher Dr. Raiz H.Y. Jiang, calling it a breakthrough in solving one of history’s greatest mysteries.