Ancient Virus DNA Was Hiding Inside Medieval Manuscripts
Researchers recovered ancient sheep pox virus DNA from animal-skin parchment in medieval manuscripts, including the roughly 1,000-year-old York Gospels. Alongside DNA from archaeological sheep remains, 21 ancient viral genomes helped reconstruct the disease’s evolution across Eurasia over at least 3,700 years.
Viral DNA was also found on calfskin and goatskin parchment, though infection or contamination cannot always be distinguished. The findings suggest manuscripts and other archives may preserve biological evidence of historical livestock diseases, linking library collections with archaeology and genetics.
For centuries, medieval manuscripts have been studied for their words, illustrations and historical meaning. Now scientists have discovered that some of these ancient books contain something entirely different: genetic evidence of a livestock disease that has existed for thousands of years.
Researchers have recovered DNA from the sheep pox virus in the animal-skin parchment used to make medieval manuscripts, including the approximately 1,000-year-old York Gospels. The discovery has helped researchers reconstruct more than 3,700 years of the virus’s evolution.
The international research team, led by scientists at University College Dublin, analysed ancient DNA from manuscripts and archaeological animal remains. Their study identified 21 ancient sheep pox virus genomes spanning roughly 1700 BCE to the early modern period, including several genomes recovered from medieval parchment.
The books were also biological records
The discovery was possible because many medieval books were not made from modern paper. Parchment was produced from animal skins, including those of sheep, goats and cattle.
That means a page of parchment can preserve biological traces from the animal whose skin was used to create it.
Scientists found sheep pox virus DNA in several historical manuscripts from Britain and continental Europe. Some manuscripts contained viral DNA on multiple pages, providing evidence that infected animals may have been among those whose skins were used to produce the parchment.
Among the manuscripts examined were the York Gospels, the Corpus Glossary, and other medieval texts dating back to around the eighth century.
The finding effectively turns some ancient manuscripts into unexpected biological archives.
The virus was even found on other types of skin
One of the more surprising parts of the study was that sheep pox virus DNA was not found only on sheep parchment.
Researchers also detected viral DNA on parchment made from calfskin and goatskin.
The scientists say there are several possible explanations. The virus could reflect unusual cross-species infections, or it could have been transferred during the process of making parchment. Contamination between animal skins was possible because parchment production involved soaking and processing hides together.
Because of that uncertainty, the researchers do not treat every positive parchment sample as proof that the animal itself had been infected.
A disease much older than the manuscripts
The medieval manuscripts provided an important part of the story, but the virus is much older than the books themselves.
The research team also analysed ancient sheep remains from Bronze Age archaeological sites in Russia and Kazakhstan. The oldest identified genetic evidence dates to roughly 1700 BCE.
Together, the samples show that sheep pox has affected livestock populations across Eurasia for at least 3,700 years.
The researchers also compared ancient viral genomes with modern ones to reconstruct the pathogen’s evolutionary history.
Their analysis suggests that major capripoxvirus lineages, including sheep pox virus, goat pox virus and lumpy skin disease virus, diverged thousands of years ago during a period when humans were increasingly managing, moving and breeding livestock across Eurasia.
What makes the discovery important?
Ancient DNA has already transformed the study of human history, migration and infectious disease. This research suggests that libraries and archives may contain another kind of historical evidence that scientists have barely begun to explore.
The pages of old books may preserve biological information about the animals, environments and diseases that existed when those books were created.
Researchers therefore believe other manuscripts could potentially contain genetic traces of ancient livestock diseases.
That could create a new connection between libraries, archaeology and modern genetics.
Instead of being viewed only as records of what people wrote, ancient manuscripts could also become records of the biological world surrounding them.
The past may still be inside the pages
The most striking part of the discovery is that the scientists did not need to find an ancient medical record describing an outbreak.
The evidence was already physically embedded in the material used to make the books.
A manuscript produced centuries ago could therefore preserve not only human knowledge, but also traces of the animals that lived alongside medieval societies.
For researchers studying diseases that still affect livestock today, those traces could provide a rare window into how pathogens changed — or remained surprisingly stable — across thousands of years.
The study shows that some of history’s most valuable scientific evidence may not be hidden underground.It may already be sitting on library shelves, inside pages that people have been reading for centuries.
