Scientists Found Ancient Virus DNA Hiding in Medieval Manuscripts

Genetic analysis of ancient parchment and archaeological remains has revealed that the sheep pox virus (SPPV) has been circulating among Eurasian livestock for at least 3,700 years. This discovery, detailed in a study published in Science Advances, underscores how historical documents serve as untapped archives of biological data, offering a window into the evolution of animal diseases long before the advent of modern veterinary science.

Led by researchers at University College Dublin, the study highlights the utility of parchment—historically crafted from the hides of sheep, goats, and calves—as a resilient medium for preserving pathogen DNA. By sampling high-profile historical artifacts, such as the 1,000-year-old York Gospels, the team successfully identified 21 ancient SPPV genomes, confirming that infected livestock were frequently utilized in the production of manuscripts.

A Millennia-Old Biological Record

The investigation traced the virus’s timeline back to the Bronze Age, identifying its presence in sheep teeth recovered from pastoralist settlements in the Eurasian steppe. Samples from sites in modern-day Kazakhstan and Russia, dating to between 1875 BCE and 1130 BCE, provided the oldest evidence of the infection. These findings suggest that the pathogen was firmly established within early domestic sheep populations as they migrated across the continent.

Sheep pox remains a highly contagious threat to agricultural stability, capable of causing significant losses in meat, milk, and wool production. Lead author Louis L’Hôte emphasized that uncovering these ancient genomes is vital for understanding the long-term evolutionary trajectory of modern pathogens that continue to impact livestock today.

While SPPV was primarily recovered from sheepskin, the researchers also detected viral DNA in calfskin and goatskin. The team suggests this may indicate rare instances of cross-species transmission or, more likely, environmental contamination during the collective processing of various animal hides in historical parchment workshops.

Remarkable Stability in Viral Evolution

The study also sheds light on the broader history of capripoxviruses, a group including goat pox and lumpy skin disease. Genetic modeling indicates that the primary lineages of these viruses diverged between 11,500 and 3,700 years ago, coinciding with the rise of sheep domestication and the expansion of trade routes across Eurasia.

Unlike the smallpox virus, which has undergone significant changes over time, the sheep pox virus appears to have maintained a notable level of genetic stability. Most critical adaptations to the host sheep were likely solidified early in the virus’s history, as the genetic signatures observed in the oldest samples mirror those found in much later historical records.

Supervising author Kevin G. Daly noted that the medieval European lineages discovered in the manuscripts are distinct from modern strains, pointing to a complex history of circulating virus populations that have since vanished. This interdisciplinary effort, involving over 30 institutions, demonstrates that historical documents are far more than just literary or legal records—they are biological time capsules.

By synthesizing ancient DNA from both archaeological sites and library collections, scientists are now better equipped to map the emergence and migration of diseases that have shaped the history of human agriculture.