For the first time, archeologists and anthropologists have identified this ancient plague in an animal: a 4,000-year-old domesticated sheep excavated in present-day Russia. The plague appears to have infected both humans and sheep that spread from a wild animal source, just like the bubonic plague. Back in the lab, the team compared the ancient Y. pestis genome from the sheep with other ancient and modern genomes. “Moreover, the ancient sheep as well as human infections are likely isolated spillovers from the unknown reservoir, which remains at large. Finding that reservoir would be the next step.”However, the search for pathogens in ancient animal remains is only just beginning.