With enormous, curved horns and a massive stature—growing over five and a half feet tall and weighing in at more than a ton—the extinct aurochs bull conjures visions of an almost mythical creature. The mighty bovine species appears throughout history, depicted in cave paintings dating back 40,000 years, featured as a symbol of strength in ancient Greek architecture, even used as a battle beast during the rule of the Roman Empire.
But the mighty aurochs, an ancestor to modern cattle, disappeared from Europe in the early 1600s. Today, scientists know little about what happened to this once-ubiquitous species.
For most of his academic career, Mikkel Sinding, a paleogenomics researcher at Trinity College Dublin, has been fascinated by aurochs. What happened to the great bovines that, only 500 years ago, roamed wide swaths of Europe, Asia and North Africa? Were aurochs hunted into extinction, or were the animals assimilated into the domestic gene pool? How closely related is the aurochs to the modern cow?
To fill some of the gaps in our understanding of aurochs evolution, Sinding looks for genetic clues from the past. Genome sequencing provides a tool to examine slight deviations in aurochs DNA, revealing how these animals lived and perhaps what drove them to extinction.
Isolating ancient DNA is hard enough. Finding a variety of aurochs DNA samples is even harder. The National Museum of Denmark—where Sinding has studied aurochs—has two complete skeletons available for testing, but the DNA from two specimens does not provide enough data to trace the genetic history of an entire European population.
Sinding and his colleague, geneticist Tom Gilbert, were speaking with a curator at the National Museum of Denmark when they came up with an idea to access more aurochs samples for DNA testing. The Copenhagen museum houses a collection of medieval Scandinavian drinking horns, some of which are large enough to have conceivably come from aurochs. Gilbert and Sinding were discussing the scarcity of testable artifacts when the curator said, “Have you not considered looking at those horns?”
“You are a genius,” Sinding replied.
Despite this early enthusiasm, Gilbert and Sinding’s team didn’t have high hopes moving forward. DNA testing can be a partially or wholly destructive process, and curators tend to frown on any research that involves chipping off or destroying part of an artifact. “We thought, ‘There’s no way in hell you’re going to be able to sample those,’” Gilbert says. But to their surprise, the museum agreed to let Sinding run his tests.
“We didn’t know if they would be aurochs horns. They were horns from a cultural collection,” Sinding says. Some of the horns in the collection date back to Greco-Roman antiquity. In the late-13th century, drinking horns experienced a resurgence in popularity among the nobility and clergy. The ornate horns—made from the hollowed keratin sheath and gilded in gold, silver or bronze—were used to decorate royal tables. The largest horn in the National Museum of Denmark’s collection was taken as a spoil of war by the Swedish army during the Polish–Swedish war of the early-17th century.
Sinding was given access to six horns from the late-14th and early-15th centuries: a hunting horn from the last aurochs bull and five medieval drinking horns. In a recent study published in The Journal of Archaeological Science, Sinding and his colleagues extracted mitochondrial DNA from these horns to create a near-complete mitochondrial genome (comprising DNA from the female line). Based on the genetic evidence and the size of the horns, Sinding and his team concluded that at least four of the drinking horns were likely taken from the last population of aurochs bulls to roam the plains of Europe. Three of the horns contained a specific genetic sequence found only in pure aurochs.
In addition to uncovering missing chapters of aurochs’ natural history, the study also inadvertently identified the museum’s collection of Scandinavian drinking horns as one of the world’s largest confirmed collections of aurochs specimens. Sinding’s work is a reminder that cultural collections at these institutions—where investigations often focus on human behavior—are also filled with artifacts made from animal skins, teeth, claws and various other remnants of extinct fauna.
Normally, scientists sample objects from natural history collections that are specifically set aside for testing. But more and more, natural history researchers and geneticists are hoping to take artifacts out from behind the glass.
By combining biology, archeology and chemistry, the field of paleogenomics has taken off, says Matthew Collins, a bioarcheologist at the University of York known for his work extracting animal DNA from Medieval parchment. There has been a “real explosion” of interest, especially when researchers realize that they “can ride on the back of advances in technology.”
Among those diving into these new research opportunities is Tatiana Feuerborn at the National Museum of Denmark. She studies the DNA in ancient clothing, specifically in garments made from the fur of sled dogs and wolves. With help from Sinding, Feuerborn navigated the museums to procure her animal skin samples.
Most of these animal samples have been sitting in historical collections, untouched, for more than a hundred years, amassed by independent explorers who traversed the Arctic to learn more about indigenous cultures, according to Feuerborn. Now she is using the clothing to study the evolution of sled dogs.
“We’re getting two different lives out of these materials,” Feuerborn says. The first life provides historical context about the dogs and the cultures that bred them. The second life gives “insight into the dog itself, its lifetime, a general idea of its genetic makeup.”
“The crazy thing is, you realize that in art galleries, museums, archives, there are lots of things which have been stored because they are either beautiful or important or even just ordinary,” Collins says. “Clothing, legal text about land, all this kind of stuff which has been made from plants and animals—linen, wool, leather, horn—it’s all carrying a biological signal too.”
For scientists like Sinding, Feuerborn and Collins, these archeological collections are brimming with overlooked data. However, many collections managers and conservators are not keen to let their priceless specimens be prodded and examined.
Collins struggled at first to get parchment samples for his research. “We talked to the head of the archives [at Cambridge University], and he thought this is a very cool idea. I hadn't bothered to speak to the conservators, who thought this was an extremely uncool idea.”
Martin Appelt, a curator of ethnographic collections at the National Museum of Denmark, is responsible for giving out permission for researchers to sample artifacts for DNA studies. Appelt always begins each project by reminding himself of a single principle: “If you decide to spend the whole artifact on some sort of destructive analysis, you’re likely not going to be able to get it again.”
At its core, DNA extraction is destructive and invasive. The extent of the destruction depends on the nature of the artifact. For Feuerborn to extract DNA from a garment, she needs a sample approximately half the size of a hole punch. Sinding scraped keratin shavings from the innermost part of the drinking horns. And Collins almost couldn’t complete his work at all—after being denied permission to directly sample the parchment, he was allowed to collect the dust that had fallen from the documents during regular cleanings.
Generally speaking, scientists understand the concerns about sampling a limited supply of historic artifacts. “I do wish that actually more museums would say no,” Collins says. “Because if you think about the degree to which collections of fossils have been sampled for the ancient DNA, if you go to museums, you'll see so many parts of the collection with little notches of bone cut or smashed out.”
As genetic sampling technologies improve, curators are working to strike a balance between conservation and research. “It’s a challenge in general that the field is working to address,” says Tim Cleland, a molecular paleontologist at Smithsonian’s Museum Conservation Institute. “With both proteomics and ancient DNA, we’re needing less and less material to work with, and as we move forward the samples will get smaller and smaller because the information is getting better.”
Even with these advances, responsible sampling of limited resources is key. Museums have been burned before by interacting with researchers, says Enrico Cappellini, professor of EvoGenomics at the Natural History Museum of Denmark. Cappellini works with rare and precious specimens, from classic paintings to thousand-year-old dental enamel. “People sometimes go to museums, approach them, get the samples, and then disappear,” Cappellini says. “If the analysis is not as successful as suspected, people don’t even bother to write a basic report for the museum for their records, and as a consequence, their willingness to provide samples is not that high.”
These basic reports are meant to help museums track the distribution of their collections, providing information about the nature of the examination and the results of the research. Unfortunately, Cappellini says, too few scientists take the time to fill out these reports.
“[The National Museum in London] had released 70-something samples for destructive analysis, and they only received reports on a handful,” Collins says. “I mean literally, five or something, and they’d only had material returned from two or three. The rest had just gone into the ether.”
Some institutions have more rigid systems in place to combat wasteful behavior. At Smithsonian museums, for example, there is “very strong policing about samples,” says physical scientist Caroline Solazzo. She explains that once a researcher gets permission to use a valuable sample, “we make sure everyone knows what the sample is going to be used for, how much is left after that, and we return samples.”
Curators are generally sympathetic to the research that scientists hope to achieve, but they are also the stewards of rare, historical objects like decorative drinking horns, historic documents and priceless garments. Researchers will always claim that their techniques are more refined or their objective truly innovative.
“There’s always a balance between what can be gained knowledge-wise and what we have to sacrifice in regard to this limited resource,” Appelt says.