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Scientists Extracted Sheep DNA from 400-Year-Old Parchment

Which is good news, because the history of humanity is intimately tied to the history of our livestock.
​Image by permission of ​The Borthwick Institute for Archives.

Ancient parchments often contain fascinating historical texts, and scientists have just figured out yet another way to pull history from their pages. As it turns out, parchment is an ideal medium for preserving ancient animal DNA—an important resource for piecing together the history of how humans and animals lived together.

Bones are often buried and subject to harsh environmental conditions for hundreds of years before scientists can get their hands on them, which makes DNA analysis difficult in many cases. Matthew Collins from the University of York and Daniel Bradley from the University of Dublin turned to parchment to overcome this hurdle.

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But parchments, which were typically made from sheep, cattle, and goat skin, are preserved in libraries, archives, and museums—making these texts perfect reservoirs for ancient DNA. Many texts are also already dated to the exact year of their writing, and there's a ton of them in existence.

The researchers estimate that even if only one percent of the animals slaughtered between 1150 and 1850 were turned into parchment (assuming the figures on record remained constant), and four percent of those skins weren't lost or destroyed, there would still be four million skins available in the UK today.

That's a lot of samples.

Collins and Bradley borrowed a small number of texts from the 17th and 18th centuries from the Bothwick Institute for Archives at York, extracted the animal DNA, and sequenced the genomes. A paper outlining their study was published today in Philosophical Transactions of the Royal Society B.

"We extracted the genomes and then compared them to modern sheep's genomic variation to see where they fell. It was a success," Bradley told me. "It turns out that parchment is an excellent substrate for historical or ancient DNA."

The team used a next-generation genome sequencing technology known as ultra-high-throughput sequencing (UHTS), that allowed them to access the entire animal genome quickly and at low cost.

"We found that there is a strong indication of change from the 1600s to the 1700s," Bradley said. "The older sheep sample looks a bit more Northern, and the later one looks a little more Southern."

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Northern sheep and Southern sheep—why should we care? Because the history of humanity is intimately tied to the history of our livestock.

Wool was a major trading good for centuries, and many of the breeds of sheep, cattle, and goats that we're familiar with today arose from the breeding practices of humans millennia ago. A sudden change in a species' genome, researchers believe, might indicate the introduction of a new breeding technique or a natural disaster.

"We want to drop a plumb line through history and ask what happened in these places," Bradley said. "In addition to chiming with known history and saying, yes, we're reinforcing what historians already know occurred, we hope to find some things in deeper history that people don't know about."

Parchment has long been considered a medium that says much more about history than what's written on it. For example, Canadian historian Harold Innis used the invention of parchment as a way to historicize shifts in how humans communicate and govern over large areas. DNA analysis adds yet another layer of historical knowledge that can be learned from these documents.

"What's written in parchment is the hardwired center of our civilization, going back a few thousand years," Bradley said. "It's really attractive to be able to add another strand of information to these often priceless artifacts."