If their technique works, it could revolutionize the use of parchment to study history. Every one of these books is a herd of animals. Using DNA, researchers might track how a disease changed the makeup of a herd or how the skin of sheep from one region moved to another medieval trade routes. It’s part of a growing movement to bring together scholars in the sciences and humanities to study medieval manuscripts.

Scientists have extracted DNA from parchment before, but this non-destructive technique expands the potential pool of research material. Archivists are loathe to allow researchers to cut off a piece of, say, the York Gospels, but some eraser crumbs? Sure. “That’s why it’s such an exciting breakthrough. It allows a lot of different manuscripts from a lot of different areas to be analyzed together,” says Bruce Holsinger, an English professor at the University of Virginia who is writing a book about parchment.

The idea to study parchment came to Matthew Collins, an archaeologist at the University of York, after a failed study in bones. A few years ago, he had a graduate student trying to extract ancient DNA from animal bones at an old Viking settlement. There were thousands of bones on the site, but only six that they tested yielded DNA—too few for any statistically significant results. “You can imagine the frustration,” says Collins.

So Collins got to thinking about archives full of old manuscripts. “You look at these shelves, and every one of them has a skin of an animal with a date written on it,” he says. Suddenly you have thousands of animals. And you didn’t even need to go out into the field and dig. When Collins and postdoctoral researcher Sarah Fiddyment first approached archives to collaborate though, they made the mistake of thinking like archaeologists used to routinely pulverizing bone for DNA analysis. “They told us we would not be allowed to sample the parchments. Matthew and I didn’t think of it,” says Fiddyment. She ended up shadowing conservationists for several weeks and learned about their eraser technique. White plastic erasers made by Staedtler turned out to be perfect for cleaning manuscripts and for collecting DNA.

Collins and Fiddyment had previously collaborated with Holsinger to use the eraser technique to study proteins from uterine vellum—so named because it is so thin that people thought that they were made from the skin of unborn livestock. Others, however suggested the skin came from different animals entirely, like squirrel or rabbit. The team published a study in 2015 analyzing proteins rubbed off of uterine vellum. They found that uterine vellum is indeed from calves, sheep, and goats, though not necessarily unborn ones.

With the York Gospels, Collins and Fiddyment went one step further to look for DNA with the eraser technique. They analyzed eraser dust from eight pages. Three of the samples yielded enough DNA to compare to modern cattle genomes, and the single most complete parchment genome was similar to modern Norwegian reds and Holsteins.