Saturday, July 25, 2015

The mammoths of Niederweningen

During the summer of 1890, a work crew employed by the Swiss Northeastern Railway labored to extend a short spur up a valley from Zurich to the far side of the tiny hamlet of Niederweningen. As they approached their goal in July, they found convenient a layer of gravel on the south side of the tracks. The layer of gravel was nothing surprising. Switzerland was well processed during the ice ages and strata of glacial till were common in the valleys. What was surprising was the bones they found beneath it.

Unlike many stories I've told here, there was no mystery about the bones. By 1890, the ice age, extinction, and Pleistocene giants were completely accepted by European intellectuals. The workers, or at least their supervisors, knew the bones were something special that needed to be preserved. The railroad might even have had a formal policy about such things. They carefully collected each bone and took it to the local inn for storage. By the beginning of August, it was clear that there were a lot of bones there. The minister of the church in nearby Dielsdorf, Pastor Schluep (I can't find his first name), sent a telegram to the president of the Zurich Antiquarian Society telling him about the find.

The telegram arrived on August 2, a Saturday. Before the day was over, Arnold Lang was in Niederweningen eager to examine the site. As soon as business opened on Monday, he met with local authorities and the management of the railway and arranged formal permission to examine the site. In a mere two weeks he organized an conducted a full excavation of the site. During that time he not only collected bones, he brought in experts to examine the geological situation and botanical remains associated with the bones. In his account, he spends more words thanking the the people who helped him than in describing the actual work—something that is personally classy but frustrating to later historians and paleontologists. The following year Lang organized a second formal excavation. Remarkably, with all time he had to plan, they found little to add to his first, tiny, improvised season.

Lang thought mammoths were the most important part of the find. In his 1892 article, he cited mammoths in his title. The description of the find was buried deep within a historical essay on mammoth discoveries. Lang writes that they identified bones from six individual mammoths (modern paleontologists say seven), one so small he thought it might be a fetus. There were also bones from wolves, horses, birds, rodents, and a woolly rhinoceros that Lang calls "the constant companion of the extinct mammoths."

Herr Dreyer, one of the experts Lang recruited, used bones from all the adult mammoths to assemble a composite skeleton which was mounted and displayed in the zoology museum at the University of Zurich. Lang's drawing shows something remarkable about Dreyer's preparation. He put the tusks on the wrong sides. This wasn't a personal quirk of his; many paleontologists thought that was the proper mounting. Look carefully at some of the artwork from the time. Though mammoths are usually shown in profile, if you study the shading you'll see that the artists were portraying outward facing tusks. Unfortunately, art directors, even at scientific magazines, still use these illustrations. This is something of a pet peeve of mine.

The Niederweningen mammoth of 1892 (source)

The paleontologists and artists of the time labored under a certain disadvantage with respect to mammoths. No one had ever recovered a skull with the tusks still attached. In Siberia, where most mammoth remains were found, the finders were allowed to take and sell the ivory before notifying the authorities. And most of them preferred not to tell the authorities at all. In Europe, skulls didn't have a very good survival rate. The skulls of elephants and mammoths are very fragile. Though they look solid, they are actually made of of thin plates of bone honeycombed with sinuses. This makes them lighter. When the skulls were dug from the ground by farmers and railroad laborers, they frequently fell apart before scientists could arrive to examine them.

But, given all the possible arrangements, why did they choose one that looks so patently absurd to us? To be fair, they didn't all believe that. The proper placement was, as we say, controversial. Several placements had been suggested. By the 1890s, quite a few had come around to the right placement. At the root of it all was a conceptual problem. Western naturalists believed that all horns, antlers, fangs, and tusks had to be functional weapons. A moose's antlers might be over-engineered because the ladies love a good rack, but, in the end, they still need to be able to give a good thrashing to any challengers. The French word for an elephant's tusks is "défenses." In fact, modern elephants don't stab with their tusks; they swing sideways and hit with them.

Another argument was that the final inward curve of an old mammoth's tusks would have blocked their vision. The growth of an a mammoth's tusks begins downward and outward. They then curve forward and the outward growth ceases. By the time they seriously curve upward, they also begin to curve inward. In some old bulls, the tips actually cross in front of their faces. And that was the problem. Some naturalists, who weren't that familiar with elephant anatomy, thought this would dangerously obstruct their vision. However, an elephants eyes are not on the front of their skull. Like most herbivores, their eyes are on the side. The line of sight that these naturalists thought would be obstructed was already a blind spot for mammoths. Still, I am charmed by the image of old, cross-eyed mammoths staggering around the tundra supported by their woolly rhinoceros buddies.

During the 2003 and 2004 excavation seasons, new digs were conducted in Niederweningen. One of them was conducted at the same site as the 1890-1 dig. Like Lang, the organizers of these digs included botanists and geologists in their teams. They also took advantage of cores drilled during the eighties that revealed the geologic strata down to the bedrock twenty meters below the village. What they discovered was that the ice age before the most recent one scoured the valley clean. During the last glacial maximum, the ice didn't reach the future site of Niederweningen. For over 130,000 years, the valley has been home to alternating lakes and peat bogs.

Lang reported that the mammoths and other bones were discovered just beneath the gravel that the railroad desired and on top of a layer of peat. His geologists dug through the peat to reveal a layer of clay and silt—lake sediment—below it. Modern geologists interpret the gravel as glacial till washed down from the surrounding mountains at the end of the last ice age. The date the transition from peat bog to alluvial plain is uncertain. There is evidence of some erosion just above the boundary. The bones have been dated to 33-34 thousand years old while the peat just below it is six to eight thousand years older. Lang found some pits in the peat that he thought might have been mammoth footprints. Of they were, they weren't from any of the mammoths he found.

Dreyer's composite skeleton is still in Zurich (they have since fixed the tusks). Many of the other bones, including the woolly rhinoceros and the baby mammoth remained in Niederweningen. The 2004 dig discovered over half of a mammoth including the jaw, tusks, most of the limb bones, and part of the pelvis. The good citizens of Niederweningen promptly built a museum for their new mammoth. Due to the richness of the site, there will certainly be future digs there. I look forward to hearing about them.

The new Niederweningen mammoth (source)

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