Timing the arrival of humans in South America remains a hotly contested topic. The earliest accepted dates are those for Monte Verde II in Chile, around 14.5 thousand years ago (kya), but numerous sites in the northern part of South America hint at earlier but more ephemeral occupations — though these are debated. One such site is Santa Elina rock shelter in Central Brazil, where possible stone artefacts and an accumulation of extinct giant ground sloth remains may indicate human presence around the Last Glacial Maximum (LGM; 26–19 kya). Now, writing in Proceedings of the Royal Society B, Pansani and colleagues add to the evidence for early human use of the site by reporting human-modified osteoderms (bumpy bony deposits from the skin of giant sloths) at Santa Elina. Although there are thousands of osteoderms at the site, the authors used microscopic and experimental techniques to determine that three were polished, perforated and flattened, possibly for use as ornaments (which use may have further smoothed the artefacts). The anthropogenic osteoderms come from the oldest layer of the shelter (dating to about 25 kya) and appear to have been undisturbed since their burial.
The Santa Elina osteoderms add to a growing body of evidence from North, Central and South America that suggests that humans arrived during, or even earlier than, the LGM. Pansani et al. speculate that, among other causes, the low density of these earliest arrivals prior to deglaciation of continental ice sheets may explain the difficulty of identifying their presence, and suggest that further multidisciplinary studies on the subject in South America are needed.
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