These Hairy Medieval Books Turned Out To Be Wrapped In Seal Skin (2025)

In medieval Europe, scribes often wrapped their books in the hairy hides of animals like deer or boar to act as protective coverings. But in some cases, they used sealskin, much to the surprise of historians.

When researchers discovered a set of 12th- and 13th-century manuscripts from northeastern France, they were puzzled because their covers did not appear to be made of the typical boar or deer skin. The hair follicles looked off.

So, a team of scientists decided to conduct some investigations. They took small samples from the covers and used techniques like mass spectrometry and DNA analysis to figure out which animals they were made from.

They were amazed to find that the books had been bound in the skins of harp seals, harbor seals, and bearded seals. The marine mammals came from Scotland, Denmark, Scandinavia, and Greenland or Iceland.

“I was like, ‘That’s not possible. There must be some mistake,” said Élodie Lévêque, the lead author of the study and a historian and book conservator at Panthéon-Sorbonne University in Paris.

“I sent it [to the lab] again, and it came back as seal skin again.”

The research team focused their investigation on books from Clairvaux Abbey in Champagne, France. The abbey was established in 1115 and contained a large library of handmade manuscripts.

It also housed an order of Catholic monks called the Cistercians, who were also known as the “White Monks” for their light-colored robes.

The team also examined books from Clairvaux’s other abbeys in France, England, and Belgium. These books were bound in sealskin as well, pointing to a strong connection between these bindings and the specific practices of those from Clairvaux.

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All the abbeys were located along European and Norse trading routes, so the skins were probably obtained through trade. Based on historical records, it is possible that Norse traders used the sealskins to pay tithes to the Catholic church.

It’s unclear why the Cistercian monks chose sealskin for their books, as the material did not seem to add any value or be related to the content of the books in any way.

The monks may not have even realized that the skins were from seals. The creatures were rarely depicted in medieval art, and during this period, there was no French word for “seal.”

That leaves the researchers to cook up their own theories and explanations for the monks’ choices. One possibility is that the Cistercians loved the color white and its subtle luxury. The skins likely came from seal pups, which are born with soft, light-colored fur.

At the time, the sealskins matched the monks’ style, but over time, the book covers have aged to become shades of brown, gray, and yellow.

The research was published in Royal Society Open Science.