Biocodicological research reveals that Cistercian libraries in the High Middle Ages sourced materials from Norse trade routes reaching as far as Greenland.
A surprising new study has revealed that dozens of medieval manuscripts from Cistercian abbeys were bound in seal skin, offering fresh insight into the materials used in book production and the extent of medieval trade networks. The research, published in Royal Society Open Science, combines techniques from archaeology, genetics, and codicology to show that the bindings of many 12th- and 13th-century manuscripts were made from the skins of harbour seals, harp seals, and even the Arctic-dwelling bearded seal.
The study, titled “Hiding in Plain Sight: The Biomolecular Identification of Pinniped Use in Medieval Manuscripts,” focuses on manuscripts from Clairvaux Abbey in Champagne, France, and its Cistercian daughter houses across Europe. Using a cutting-edge method known as eZooMS (electrostatic zooarchaeology by mass spectrometry), alongside ancient DNA analysis, researchers identified the animal origins of 19 manuscript bindings. To their surprise, many of these “hairy” bindings once catalogued as deer or boar turned out to be from seals.
“This integration of the biological sciences into the study of historical manuscripts not only provides a clearer picture of the material culture of medieval Europe, but also illustrates the extensive trade networks that Cistercian monasteries were part of,” the authors write.
🧵 Is this a Dire wolf… 🤔?
No…
Our @erc.europa.eu Beasts to Craft team led by Élodie Lévêque uncovered the true identity of mysterious hairy covers on #medieval #Cistercian #manuscripts – they’re …
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— Matthew Collins (@matthewcollins.bsky.social) April 9, 2025 at 2:04 AM
Seal skin was not a local material for Champagne, a region with no seal populations or nearby coastlines. Instead, DNA analysis of the skins traced their origins to Scandinavian, Scottish, and Greenlandic populations. One sample, from the binding of a manuscript held at St Omer, was identified as harp seal and most closely matched animals from the Greenland Sea. Another was from a bearded seal—an Arctic species rarely found in Europe. Most other samples came from harbour seals, including individuals genetically linked to Norway, Denmark, and northern Scotland.
The presence of these skins in French and Belgian monastic libraries suggests that the Cistercians were plugged into expansive commercial routes—some of them Norse in origin—that moved not only ivory and furs but also less well-documented commodities such as seal leather. These routes included the Hanseatic League and the Champagne fairs, where monks from Clairvaux were known to trade.
Clairvaux, founded in 1115 by Saint Bernard, was one of the most important monasteries of its time, and by the early 14th century it held around 1,000 volumes. Roughly half of the surviving manuscripts from Clairvaux remain in their original bindings, many of which include a secondary cover or chemise made of fur-covered skin. While these chemises were once believed to be made from deer or boar, visual and microscopic analysis failed to confirm this, prompting the application of biocodicological techniques.
1/🧵 Seals! 🦭
We analyzed 16 manuscripts (12th-13th c.) from Clairvaux Abbey (France) using # ZooMS and ancient DNA 🧬.
What was once thought to be deer 🦌or boar 🐗 turned out to be various seal species from far northern waters!
— Matthew Collins (@matthewcollins.bsky.social) April 9, 2025 at 2:04 AM
Protein and DNA evidence pointed clearly to pinnipeds, and the discovery aligns with references from Norse sources that document the use of seal products—including skins—as part of trade, tribute, and even ecclesiastical tithes. One 13th-century record describes a tithe collector returning from Greenland with “a substantial amount of seal and ox skins, cetacean teeth, whale baleen and leather ropes.” These goods were accepted by the Church due to a shortage of currency.
This surge in sealskin bindings appears to have peaked around the year 1200 and declined sharply before 1300. The authors suggest this may reflect both changing trade patterns and the impact of climate change. As the Little Ice Age took hold, Norse settlements in Greenland collapsed, and their sea hunting practices—unlike those of the indigenous Thule people—were not well suited to increased sea ice conditions.
There’s also the matter of aesthetics. Cistercians were known for their white habits and taste for unadorned simplicity, and sealskins—especially those from younger animals—could appear light grey or off-white. Today, the skins look brown due to degradation, but under magnification, many retain their original pale hues.
2/🧵 The big revelation? DNA analysis traced these skins to harbor seals from Scandinavia and Scotland, harp seals from Iceland/Greenland, and even a bearded seal (a strictly Arctic species)! This shows Cistercian monks were connected to extensive Norse trade networks.
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— Matthew Collins (@matthewcollins.bsky.social) April 9, 2025 at 2:04 AM
Interestingly, the monks may not have even known what kind of animal the skins came from. The seal was a little-known creature in medieval France and was rarely depicted in bestiaries or heraldry. As the authors note, “the monks may not have associated the skins covering their manuscripts with the animal described in medieval bestiaries as the ‘sea calf.’”
In total, 43 bindings were examined across France, Belgium, and England, most of them from Cistercian monasteries. Though many chemises have not survived intact, the researchers found stitch marks and skin remnants on additional volumes, suggesting that seal skin bindings were once far more common than we can see today.
This research not only redefines our understanding of Cistercian manuscript production but also demonstrates the power of interdisciplinary approaches. By treating books as biological as well as cultural objects, scholars can unlock new stories hidden in the materials themselves—stories of forgotten animals, Arctic hunters, and the long reach of medieval trade.
4/🧵 These books offer a stunning window into medieval globalization. Bookbinding materials weren’t just local – they came from thousands of miles away, through complex trade routes that linked Arctic hunters to mainland European monasteries.
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— Matthew Collins (@matthewcollins.bsky.social) April 9, 2025 at 2:04 AM
As the authors write, “Contrary to the prevailing assumption that books were crafted from locally sourced materials, it appears that the Cistercians were deeply embedded in a global trading network.”
The article, “Hiding in plain sight: the biomolecular identification of pinniped use in medieval manuscripts,” by Élodie Lévêque, Matthew D. Teasdale, Sarah Fiddyment, Maiken Hemme Bro-Jørgensen, Luke Spindler, Ruairidh Macleod, François Bougard, Morten Tange Olsen and Matthew Collins, appears in Royal Society Open Science. Click here to read it.
6/🧵 105 Romanesque bindings (63% of the collection!) originally had sealskin chemises, though most have disappeared with only traces remaining.
Similar bindings in other “daughter houses” of Clairvaux across Europe.
Full paper in RSOS:
#medieval #manuscripts #biocodicology #tradeNetworks[image or embed]
— Matthew Collins (@matthewcollins.bsky.social) April 9, 2025 at 2:04 AM
Top Image: Romanesque binding from Clairvaux covered with a chemise with hairs on (Médiathèque du Grand Troyes, ms. 35, ca. 1141−1200), sample EL53. Courtesy Royal Society Open Science. Bibliothèque Municipale de Valenciennes, MS 320 fol. 120r
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