Ancient sheep virus found hiding in medieval parchment.

In a study published in Science Advances, researchers pin the virus' emergence to about 5000 years ago, roughly the same time people started to intensively shear sheep for wool. "I was so jealous when I saw this paper," says Floris Breman, an evolutionary biologist at the Belgian national health agency Sciensano, because he wished he could have made the discovery. "It's very important because it shows us how viruses arrive in a population." The peek into the pathogen's past came from an unusual source: dozens of medieval books and legal documents written on parchment, which is made from specially treated animal skins. "It turns out parchment is an extremely good preserver of this type of biological data," says University of Leicester historian Joanna Story, a co-author of the new study.