Monday, June 03, 2013

Leibniz's unicorn

Otto von Geuricke was not a fool. During his lifetime he was a philosopher, diplomat, Mayor of Magdeburg for thirty-one years, and a respected scientist and inventor. It was for his work the last two capacities that he is probably best remembered. Geuricke invented the vacuum pump and performed public experiments with it that made him a welcome member of the European scientific elite. With that resume, it might surprise modern readers to find him calmly describing a unicorn in his main scientific work before moving on to more important topics.

His description is short. In its entirety, it reads:
It happened in the year 1663 in Quidlinberg, that on the Mountain the common people call Zeunickenberg, where lime is mined, inside the rock a unicorn skeleton was found. The rear portion of the body, as is common in a beast, lay back, head up, but, extending lengthwise from the brow was a horn, the thickness of a human leg, and so in proportion to the length of almost five cubits. Primarily through ignorance, the skeleton of the animal was broken and extracted in pieces. Together with the head with the horn and some ribs, spine, and bones, were given to the Reverend head abbess of the place.
The passage gives no indication whether Geuricke ever saw the bones himself, though he had plenty of opportunity to do so. Quedlinberg is less than thirty miles from Magdeburg and much of Guricke's technical innovation was aimed at making mining safer and more efficient, so he must have visited the mining regions. However, there is nothing in his writings to indicate that he ever looked further into the story. Guericke was an important enough scientist that his books were read and discussed by the scientific elite all over Europe. The Quedlinberg unicorn was mentioned a few times over the next few years and would have been forgotten except for the fact that the great Gottfried Wilhelm von Leibnitz repeated the story and produced a drawing of the skeleton.

In the years 1691-3, Leibniz was working on a geological history of that part of Germany as a Michener-style prologue to his history of the house of Brunswick and their lands. A large part of his work dealt with fossils. The presence of entire strata of salt water seashells on high ground disturbed and intrigued Seventeenth Century natural philosophers. Leibniz catalogued and analyzed the shells in his region. Following that, he looked at some of the other difficult organic remains buried in the mountains. Buried ivory was right at the top of the list.

Buried ivory had several names, one of the most common, at least to people who spoke Latin, was "unicornu fossili"--fossil unicorn. At that time, the word "fossil" was evolving from its original meaning of "something from the ground" into its modern meaning of "petrified organic matter." Another transformation happening at the time had to do with the word "unicorn." The belief in, and giving a damn about, the animal unicorn peaked during the Renaissance. Unicorn horn was a protection against poisons and a universal antidote should you be poisoned. No one was anyone unless someone wanted them dead. Unicorn horn’s medical powers were not limited to poison. It was also useful in treating “Scurvy, Old Ulcers, Dropsie, Running Gout, consumptions, Distillations, Coughs, Palpitation of the Heart, Fainting Fits, Convulsions, Kings Evil, Rickets in Children, Melancholly or Sadness, The Green Sickness, Obstructions, and all Distempers proceeding from a Cold Cause." Fragments of unicorn horn were worth more than their weight in gold. A complete horn was worth more than a medium sized town.

Its very success doomed the unicorn. Nothing about the unicorn could stand up to extended scrutiny. From one side, physicians questioned the idea of a universal antidote. Nature was composed of pairs of opposites, hot vs. cold, wet vs. dry. How could the same medicine counteract a wet poison and also a dry poison? Naturalists hunted the world for the unicorn animal and found hints and claims, but no actual unicorns. By the late Seventeenth Century, faith in the existence of an actual unicorn animal was fading fast. Several different writers demonstrated that the straight spiral horn, so beloved by medieval artists, actually came from a sea animal caught in the icy waters surrounding Greenland. Other pieces of unicorn horn were shown to be walrus tusks, elephant ivory, or cheaper substances such teeth and bones of farm animals. The last great hope for unicorn believers was fossil ivory. Finding ivory in the ground was pretty amazing. Guericke adhered to the belief that it actually grew there. Not that it was a plant, but that it was real ivory created by some generative power within the earth. If fossil ivory had such had such a wonderful origin, crediting it with diverse medical powers was no great stretch of the mind.

When Leibniz repeated Guericke’s story, he made it clear that, in his opinion, unicornu fossili was the remains of real animals. What’s more he was sure it was the remains of known animals. He allowed that in rare cases it might ivory of elephants washed into the North by the Biblical deluge, but he confident that in most cases it was the remains of walruses and narwhals that had lived there when the shoreline of the North Sea was far to the south of its present location. Still, Guericke was a man of impeccable reputation and the story was an interesting one. Following his recounting of the story as told by Guericke, Leibniz added: “The same has been reported to me. An illustration was added which it is not inappropriate to submit here.”

Leibniz’s unicorn. Source.

Leibniz never finished his history. In fact he never went any further than writing the geological preface. Both the text and the drawing sat in his papers until 1749, over thirty years after his death. In that year, Ludwig Scheidt, the librarian of the house of Brunswick, edited the treatise into chapters and had the drawings Leibniz had collected engraved onto printing plates. The result was published in Latin and German as Protogaea, or A Dissertation on the Original Aspect of the Earth and the Vestiges of Its Very Ancient History in the Monuments of Nature. The unicorn appeared on the same page as the tooth of a mammoth (referred to as that of a “marine animal”) and carried the caption “Image of a skeleton excavated near Quedlinberg.”

The image and description have gone on to become quite famous. While the bizarreness of the image has a lot to do with that fame, the image has a valid claim to being a significant milestone in paleontology. Science writers often call it the first paleontological reconstruction. To call it that, requires a few qualifiers. Every time a medieval parish priest laid out some large bones and imagined his village had discovered a giant, he was making a paleontological reconstruction of sorts. What made the Quedlinberg unicorn special was that published and directed at a scientifically literate audience.

But that’s not the whole story of the Quedlinberg unicorn. Over the years, both Guericke and Leibniz have been credited as the artists. Guericke is an unlikely source. His book was well illustrated and, if he found the story interesting enough to add to his book, it seems that he would have used the illustration if he had had it in his possession. Leibniz is definitely not the artist. He explicitly says he received the drawing from an unnamed person whose account backed up Guericke’s. As I mentioned above, Leibniz and Guericke was not the only writers to draw attention to the story. The most interesting publication happened in 1704, while Leibniz was still alive. In a catalog and commentary on the great collections of Europe, Michael Bernard Valentini published a version of the reconstruction. Valentini wrote that the illustration was based on a sketch by Johann Mäyern, a counselor at Quedlinberg. Valentini’s illustration is of much lower quality than Leibniz’s. Was Mäyern Leibniz’s other source or was there a third drawing that they both copied? Unless Mäyern’s original drawing shows up, we will probably never know.

Valentini’s unicorn. Source.

In the early Twentieth Century, the Austrian paleontologist Othenio Abel took an interest in the Quedlinberg unicorn. Abel had already casually mentioned the story in several of his books before he decided to get serious and try to figure out what the skeleton really was. They actual bones had long since disappeared and no other drawings or descriptions had ever been made of them. The best evidence he had to work with was Leibniz’s drawing. Abel immediately recognized that this not a single skeleton that had been reassembled in a whimsical manner. The bones came from at least two individuals and two different species. The skull is that of a woolly rhinoceros. The teeth, scapulae, and vertebrae are from a mammoth. Most of the spine has been reassembled backwards and upside down. What at first glance look like ribs are really dorsal spines that are part of the individual vertebrae. The loop at the bottom is the first cervical vertebra. And the horn; what is the horn? It’s too long to be a walrus tusk and too wide to be a narwhal tooth, Leibniz’s preferred explanation for fossil ivory. Rhinoceros horns are not made of bone or ivory. They’re made of keratin, the material as hair and finger nails. It’s unlikely that the learned burgers of Quedlinberg would have mistaken that for a unicorn horn. That leaves a mammoth tusk, which easily meets the length and width requirements. It takes a little more speculation to explain its being straight and not curved. There are two possibilities here. One is that the tusk was badly enough broken up that the people who reassembled it had the freedom to make it any shape they wanted. The other possibility is that it came from a different kind of extinct elephant, such as the palaeoloxodon, a species that went extinct about 15,000 years before the mammoth and that had much straighter tusks.

There is a cave near Quedinberg called the Einhornhöhle or Unicorn Cave. Even before the gypsum miners on Zeunickenberg found their strange skeleton, the locals had been bringing bones out the local caves and selling them to apothecaries as “genuine” unicorn horn. This explains why the Quedlinberg burgers had unicorn on their minds as they tried to make sense out of a pile of broken bones. No doubt, someone had the idea of getting in on the unicorn trade. But the price of unicorn horn was crashing in the late Seventeenth Century and any plans they might have had never came to fruition. Leibniz visited the area in 1686 and crawled through several caves, but didn’t find any unicorns, which explains his noncommittal tone when he repeated Guericke’s story six years later.

That’s not the end of the story. In the Nineteenth Century, paleontologists explored the caves in the Harz Mountains and identified the bones of dozens of species of Pleistocene mammals. In the Twentieth century, the local governments realized the tourist potential of the caves and dug comfortable entrance tunnels into them. There are several small museums in the region proudly showing off the bones. There are several full sized models of the unicorn on display. One of them guards the entrance to the Einhornhöhle. Tourist shops sell paperweights and t-shirts adorned with Leibniz’s drawing. The Quedlinberg unicorn lives on.

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