You don’t often hear about sheep pox. According to Wikipedia, it’s “the most severe of all the animal pox diseases.” Luckily, it was eradicated from continental Europe in the 20th century, though it still pops up here and there; for example, a study published in Science Advances found sheep pox in DNA extracted from a medieval parchment.
Books back then were all bound by animal skins. Geneticists literally rubbed pencil erasers against ancient pages to lift genetic residue, because we live in a wondrous age of science where the minute traces of DNA on ancient pieces of paper have nowhere to hide, creating not just a textual archive but a kind of biological one, too.
Guys who were scribbling down 1000-year-old Gospels in books made of sheep, goats, and cows were inadvertently creating a permanent biological record of the entire pasture.
Scientists Found Ancient Virus DNA in Books That Are Nearly 1,000 Years Old
By pairing this codex residue with ancient sheep teeth from Bronze Age sites in Russia and Kazakhstan, the international team reconstructed 21 ancient viral genomes that spanned over 3,500 years. All the new data pushes the sheep pox pathogen’s timeline back around 5,000 years, to the era when Eurasian humans started densely packing sheep together to shear them for wool. Turns out, cramming a bunch of any kind of animal together in one giant disgusting slop pile is not a great idea, as it creates a breeding ground for disease.
The researchers also found the viral DNA on pages made of calfskin, goatskin, and paper, indicating that there is some kind of cross-species contamination going on, or maybe that medieval parchment makers were binding pages with infected animal glue gelatin.
Despite a history of brutal outbreaks that wipe out up to 80 percent of a herd’s young, the sheep pox genome has remained stubbornly stable across millennia. That genetic persistence is crucial context right now, as modern farmers—like those battling ongoing livestock outbreaks in Greece—fight the exact same biological menace that medieval monks unwittingly bound into their holy texts.
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