Terrifying news of the day alert. Using tiny fragments of DNA from two German victims killed by the Justinian plague about 1,500 years ago, scientists were able to reconstruct the genome of the oldest known bacteria. Through their work, they realized not only the Justinian Plague but the Black Death, which killed about 50 million Europeans in four years, were both caused by a strain of the pathogen Yersinia pestis. And the lucky human race in 2014 is still pretty vulnerable to these catastrophic outbreaks, warn experts. "What this shows is that the plague jumped into humans on several different occasions and has gone on a rampage," said Tom Gilbert, a professor at the Natural History Museum of Denmark. "That shows the jump is not that difficult to make and wasn't a wild fluke," Gilbert said.