I cited Swedish explorer Erland Nordenskiold in a post last week and forgot to mention the role he played in one of the last great natural history adventures of the 19th century.
In 1895 a former merchant sea captain named Hermann Eberhardt, farming on the shores of a inlet called Ultima Esperanza (“Last Hope”) in southern Chile discovered a giant cave on his property. Inside he found a large fresh-looking skin covered with long reddish-gray hair and embedded with bean-sized bones. Scientists identified it as that of an extinct Mylodon ground sloth. Further excavations uncovered bones with bits of dried tissue still attached, plus evidence of human habitation.
Today we know the bones and skin were preserved by the climate inside the cave, but to Professor Florentino Ameghino of the Buenos Aires museum, the skin appeared fresh. He remembered a story a friend had told him of seeing a strange animal while exploring in the area. Ameghino linked the story and the skin to a legend of a large nocturnal beast local natives called iemisch, with giant claws it used to dig burrows where it slept during the day. Ameghino concluded the iemischwas a living Mylodon ground sloth. His announcement created a world-wide stir. (Ameghino, 1898)
Erland Nordenskiold was a voice of reason in the hullabaloo and conducted the first systematic excavation of the cave. However, publication of his study only added fuel to the fire. He determined the evidence of human habitation lay in a distinct horizon above and separate from the older lower horizon with its sloth bones, dung and dried grass.(Nordenskiold, 1900). Modern radiocarbon dating of the dung indicates the cave was occupied by sloths from about 13,500 years B.P. to 10,500 B.P. (Markgraf, 1985).
Others concluded from the large quantities of the dung and finely chopped “hay” that sloths had been kept captive inside the cave by natives fattening them for slaughter, behind the stone wall Nordenskiold had reported. Some even suggested the sloths had been domesticated (Allen, 1942). Today we know the sloth “corral” was merely fallen rock from the ceiling (Naish, 2005)
In 1900 the Daily Express sponsored an expedition to Patagonia to capture a living Mylodon. The venture was mismanaged however and the leader, HV Hesketh-Prichard, quit before reaching the cave. He dismissed the idea as a hoax (Hesketh-Prichard, 1902).
Nordenskiold offers us a lesson on the sloth project–finding three sloths in close proximity doesn’t make them a familyno matter how good it looks. Only careful excavation, painstaking attention to stratigraphy and detailed chemical analysis will do that. . . . Dave
References
Ameghino, F. 1898. An existing ground-sloth in Patagonia. Natural Science 13: 324-326.
Heuvelmans, B. 1995. On the Track of Unknown Animals. R. Garnett (transl.) Kegan Paul International.
Markgraf,V. 1985. Late Pleistocene faunal extinctions in southern Patagonia. Science 228: 1110-1112.
Naish, D. 2005. Fossils explained 51: Sloths. Geology Today 21: 232-238.
Nordenskjold E. 1900. La grotte de Glossotherium (Neomylodon) de Patagonia. Bulletin de la Societe Geologique de France: 29: 1216-1217.
On a research trip to London a few years ago I had the opportunity to work with those bones of Mylodon and they still look remarkably fresh, even a hundred some years after their discovery.
Although it may not be possible to relate those sloths in a familial context, that there is a range of specimen ages does provide new insights in to patterns of growth and development with this species. These specimens helped solidify a pattern of loss in the upper caniniform that was marginally evident in the adults, via vague outlines of avleolar closing.
This same potential for age-related studies exists with the Tarkio sloths as well.
Further sloth history: At the time of Nordenskiold’s discovery, the genus of Mylodon was in the midst of its hefty taxonomic confusion and was currently called Grypotherium. Due to the perceived idea that these sloths were being kept in a coral by humans, the species became known as Grypotherium domesticum. This name has since been synonymized with M. darwini when the last of the taxonomic issues were sorted out between that genus and Glossotherium.