A significant discovery in southern Uruguay has raised questions about the timeline of human interaction with megafauna in the Americas. The 33,000-year-old bone of a giant ground sloth, found in Arroyo del Vizcaíno, exhibits distinct markings that may have been caused by human activity. This find suggests that humans could have been hunting these massive creatures much earlier than previously believed. The bone shows a deep, conical indentation, and further analysis points to possible human-made tools. According to Archaeology Magazine, this discovery could push back the earliest evidence of human presence in South America, altering our understanding of early human history on the continent.
A Remarkable Find: The Fossil and Its Mysterious Wound
The fossilized right calcaneus (heel bone) of the Lestodon armatus, a species of giant ground sloth, was unearthed from a dense bone bed containing over 2,000 remains, predominantly from L. armatus.
This particular specimen, known as CAV 45, is notable for its unusual indentation—a deep, cone-shaped depression measuring 21 mm in diameter and 41 mm in depth. The smooth edges and conchoidal fractures of the mark strongly suggest the bone was penetrated with force, potentially by a human-made weapon.
Human-Made or Natural? The Clues Point to Humans
Researchers employed cutting-edge techniques like CT scanning and silicone casting to examine the injury. They discovered microscopic striations inside the cavity, revealing that the object that created the wound rotated and shifted laterally as it was driven in.
The fact that organic fibers, including plant materials, were found lodged inside the indentation hints that this trauma could have been caused by a hardened wooden shaft, potentially with a bone, ivory, or hardwood point. These features are consistent with human-made tools used for hunting.
In the process, researchers also ruled out several alternative causes for the indentation. They compared the wound to marks that might be caused by carnivore bites (such as those from saber-toothed cats or giant bears), erosion, or accidental impacts.
None of these causes fit, as the marks from carnivores would have specific tooth shapes, and accidental impacts would typically result in irregular fractures, not the clean, cone-shaped hole observed here.
A New Timeline for Human–Megafauna Interactions?
This fossil challenges the conventional wisdom that humans arrived in the Americas around 23,000 years ago. With the evidence pointing to human activity as early as 33,000 years ago, it suggests that humans were hunting megafauna well before the Last Glacial Maximum (LGM), which occurred between 26,500 and 19,000 years ago. The findings align with other pieces of evidence pointing to earlier human presence in South America, offering a more complex narrative of human migration and megafauna extinction.
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