Ground Sloth Femur. Source: Cleveland Museum of Natural History
The role of humans in the extinction of megafauna, including mammoths, mastodons, and ground sloth, at the end of the Pleistocene is one of the more contentious issues in Paleo-Indian studies. Brian Redman, of the Cleveland Museum of Natural History, and his colleagues report the first direct evidence of human-made stone tool cut marks on a Jefferson’s ground sloth (Megalonyx jeffersonii) bone. If the identification of the cut marks is correct, it indicates that humans likely hunted ground sloths.
Ten ground sloth bones were excavated from a swamp in Norwich Township, Ohio in the early twentieth century and were curated at the Firelands Historical Society Museum in Norwalk, Ohio. It was not until recently that researchers at the Cleveland Museum of Natural History reexamined the bones and identified possible stone tool cut marks on one of the bones, a femur. More in-depth research ensued.
The researchers first nailed down the context of the finds. Labels associated with the bones and brief mention of what appeared to be the same finds in early twentieth century paleontological reports by Oliver Hay indicated that a college student named Roe Niver discovered the specimens in a bog on his family’s property in Ohio. The researchers were able to relocate the small bog from which the bones were likely excavated.
They identified 41 individual tool marks using 15x to 100x magnification and, for a smaller sample, scanning electron microscopy, all of which are on the anterior side of a femur. None of the nine other ground sloth bones have any possible tool marks. Based on the morphology of the marks, they infer that most of the marks were made by humans using unmodified stone flakes or blades to remove meat from the leg bone. Unifacial and bifacial retouched stone tools were used to make some of the cut marks, indicating more than one tool was used on the ground sloth.
Botanical material found within the ungual sheaths of two of the bones contained fragments of conifer wood, possibly from spruce, Douglas fir, or tamarack. These tree species are consistent with the inferred environment at the end of the Pleistocene. The ground sloth bones date to 11,740 +/- 35 years before present (calibrated range of 13,738-13,435 years BP) based on an AMS radiocarbon date from one of the bones. They therefore are the “most ancient possible evidence of human activity in Ohio” (Redmond et al. 2012:94). This date is also slightly earlier than the current age range of the Clovis culture.
Cut marks or other direct evidence for human predation on most species of extinct megafauna in the Americas is surprisingly scarce. A few examples of predation on a different species of ground sloth in South America have been reported, but the Ohio example reported in this article is the first good evidence that humans preyed on Jefferson’s ground sloth. It is a small but important contribution to the larger question of whether human predation was a major factor in the extinction of the megafauna.
Brian G. Redmond, H Gregory McDonald, Haskel J. Greenfield, Matthew L. Burr. New evidence for Late Pleistocene human exploitation of Jefferson’s Ground Sloth (Megalonyx jeffersonii) from northern Ohio, USA. World Archaeology, 2012; 44 (1): 75-101.