Animal origin of 13th-century uterine vellum revealed using noninvasive peptide fingerprinting

Significance This study reports the first use, to our knowledge, of triboelectric extraction of protein from parchment. The method is noninvasive and requires no specialist equipment or storage. Samples can be collected without the need to transport the artifacts; instead, researchers can sample when and where possible and analyze when required. The level of access we have achieved highlights the importance of this technique. For this study, we have extracted proteins from 513 parchment samples, used to resolve the long-standing question of the origin of “uterine vellum.” We find no evidence of unexpected species, such as rabbit or squirrel. We suggest that uterine vellum was often an achievement of technological production using available resources, and would not have demanded unsustainable agricultural practices. Tissue-thin parchment made it possible to produce the first pocket Bibles: Thousands were made in the 13th century. The source of this parchment, often called “uterine vellum,” has been a long-standing controversy in codicology. Use of the Latin term abortivum in many sources has led some scholars to suggest that the skin of fetal calves or sheep was used. Others have argued that it would not be possible to sustain herds if so many pocket Bibles were produced from fetal skins, arguing instead for unexpected alternatives, such as rabbit. Here, we report a simple and objective technique using standard conservation treatments to identify the animal origin of parchment. The noninvasive method is a variant on zooarchaeology by mass spectrometry (ZooMS) peptide mass fingerprinting but extracts protein from the parchment surface by using an electrostatic charge generated by gentle rubbing of a PVC eraser on the membrane surface. Using this method, we analyzed 72 pocket Bibles originating in France, England, and Italy and 293 additional parchment samples that bracket this period. We found no evidence for the use of unexpected animals; however, we did identify the use of more than one mammal species in a single manuscript, consistent with the local availability of hides. These results suggest that ultrafine vellum does not necessarily derive from the use of abortive or newborn animals with ultrathin hides, but could equally well reflect a production process that allowed the skins of maturing animals of several species to be rendered into vellum of equal quality and fineness.