Post-doc Bart Lambert reports on how to get DNA from the York Gospels without destroying the tiniest piece of parchment.
One of the most valuable items held in the collections of the York Minster is the so-called York Gospels, an Anglo-Saxon manuscript. Despite its name, most of the book was probably produced at St Augustine’s monastery in Canterbury around 990AD. It was then brought to York by Archbishop Wulfstan, one of the leading churchmen and intellectuals of his day, in around 1020AD. This makes the York Gospels one of the few surviving relics of York’s original, Anglo-Saxon Minster, which, replaced by the current Norman and gothic cathedral, has now completely disappeared and whose exact location is unknown. Beautifully illustrated, the manuscript contains the four gospels of the bible, the accounts of the lives of Jesus Christ believed to have been written by St Mark, St Matthew, St John and St Luke, and a number of documents about land ownership, including a letter from Cnut the Great, King of England, Denmark and Norway in the early eleventh century. Arguably the most important part of the book, however, is that which contains the oaths taken by the deans, archdeacons, canons, vicars choral and other dignitaries of York Minster upon their installation. Dated to the 14th century, this part of the document is still used in ecclesiastical ceremonies, such as the inauguration of the current archbishop, John Sentamu, in 2005.
Even though the York Gospels have been the object of academic scrutiny for decades, a recent study by an interdisciplinary team including CitiGen researchers Matthew Collins (Universities of York and Copenhagen) and Dan Bradley (Trinity College, Dublin) has significantly expanded our knowledge of the Anglo-Saxon document. The potential for biomolecular research offered by ancient manuscripts such as the York Gospels is enormous. Made of parchment, or, quite literally, a relatively well-dated collection of animal skins, they provide a store of biological information. They are also interesting resources for the collection of ancient human DNA: over centuries – in the case of the York Gospels even for more than a millennium – they were used by a variety of people, many of whom left a genetic mark on the object. Yet the study of parchment documents is also strongly limited by the requirements of manuscript conservation. Because of their precious and highly vulnerable nature, libraries and archives usually do not allow samples to be taken from their manuscripts. Apart from their use in church ceremonies, the York Gospels are usually stored away safely behind glass in the Undercroft exhibition area of the York Minster.
Collins’ and Bradley’s team overcame these issues by developing a sampling method which is not only compatible with the needs of manuscript conservation, but could also be carried out in tandem with it. Dry cleaning of the surface of parchment documents with PVC erasers is a widely used conservation technique. The team analysed the waste material from this process, which would otherwise be discarded. They were able to recover DNA from humans who used the manuscript and swore oaths on its pages throughout its 1,000-year history and from bacteria that probably originated from the hands and mouths of those people. They also found DNA from the animals that were used for the production of the parchment. Seven of the eight pages studied were made of cow skin, one of sheep skin. Some of the samples provided enough DNA to compare to the genome of modern cattle and the most complete genome from the parchment was similar to that of Holsteins and Norwegian Reds, cattle breeds that are now common in northern Europe. The sex of the calves could be determined for five of the eight pages. For four out of these five, the animal used turned out to be female. This is remarkable, as female calves were more indispensable to the preservation of cattle herds because of their reproductive value. The producers of the manuscript could have used skins of animals that were not slaughtered purposefully but had died from other causes. Historical records make clear that in the years before 990AD, the date most commonly accepted for the composition of the York Gospels, a major cattle plague swept across the British Isles. An alternative explanation is that the selection of female animals reflects the choice of the most exclusive material for a manuscript that contains the holy word.
The eraser-based sampling method adopted in the analysis of the York Gospels can now be used to investigate other documents and has the potential to completely revolutionise the study of ancient manuscripts. In combination with the work of researchers from other disciplines, the recovery of DNA from parchment can provide us with insights into many aspects of manuscript production which have so far remained largely obscured, such as the often centuries-old use history of the object, the decisions made in its production and even the past composition of cattle herds. And all of that, without destroying the tiniest piece of parchment.
If you enjoyed this post, sign up below to have future blog posts from CitiGen delivered straight to your inbox!