Giant Sloth Pendants Push Back Timeline of Humans’ Arrival in South America

Archaeologists in Brazil say they have unearthed 25,000- to 27,000-year-old pendants made of bony material from the extinct giant ground sloth Glossotherium phoenesis.

An artist’s impression of the Santa Elina rock shelter, Brazil. Image credit: Júlia D’Oliveira.

“Most Pleistocene megafauna — mammals with body mass greater than 44 kg — became extinct worldwide by the Pleistocene-Holocene transition,” said senior author Dr. Mírian Pacheco of the Universidade Federal de São Carlos and colleagues.

“The decline and eventual extinction of these megamammals are generally linked to human impact and climate change, but this is a still hotly debated topic for South America.”

“Recent studies have raised new perspectives about human arrival in South America around the Last Glacial Maximum (19,000-26,000 years ago), as well as on its impact on the megafauna there.”

“However, whereas it is currently well accepted that peopling of the Americas happened earlier than the Clovis culture (13,500 years ago), skepticism about human occupation of the Americas earlier than 16,000 years ago still persists.”

“Questions regarding the timing and routes for human dispersal into the Americas remain open to debate, but human dispersal probably followed multiple routes and time frames, including Pacific coastal and inland (ice-free corridor) routes.”

“In this scenario, Late Pleistocene sites containing evidence of early human occupation in South America should be closely scrutinized with interest.”

In their research, the archaeologists examined three modified osteoderms — bony plates embedded in the animal’s skin — of the giant ground sloth Glossotherium phoenesis.

The specimens, which are between 25,100-27,400 years old, were found in the Santa Elina rock shelter in the Brazilian state of Mato Grosso.

The site also yielded a rich and diverse assemblage of human-made limestone and calcite flakes, quartz and silex items, some of which could have been used by humans to perform bone surface alterations.

“The Santa Elina rock shelter in Central Brazil displays a rock panel rich in paintings, including anthropomorphs (e.g. ‘men with ornaments’), and zoomorphs such as birds, deer, monkeys and tapir,” the researchers explained.

“Dated mineral pigments and bonfire structures associated with stone tools and megafaunal remains found in the shelter include Late Pleistocene to the Holocene ages.”

“The only Pleistocene megafauna present in the shelter are two extinct giant ground sloths of the species Glossotherium phoenesis, in two different archaeological layers.”

“Along with the giant sloth bones, there are thousands of osteoderms, which are dermal bones once embedded within the skin of the animal.”

Geological setting and archaeological context of Santa Elina: (a) geographic location of Santa Elina in Brazil (in red), and other selected archaeological sites with evidence for an early human occupation in the Americas; (b) panoramic view of the rock shelter; (c) excavation areas; (d) schematic representation of the archaeological layers at the site, indicating the presence of stone tools, ground sloth remains, fire structures, and wall paintings; (e) selected elements found at the site, including giant sloth osteoderms: unmodified osteoderm (g), possibly burnt bone fragment (h) and three osteoderms modified into artifacts (i-k). Scale bars – 1 cm. Image credit: Pansani et al., doi: 10.1098/rspb.2023.0316.

The team performed a traceological analysis of the three osteoderms from the rock shelter using optical microscopy, non-destructive scanning electron microscopy, photoluminescence and synchrotron-based microtomography.

The presence of several marks from human modification, including drilled perforations, polishing, multi-directional scratches and use-wear traces, suggests their anthropic nature and extensive use.

This provides additional evidence for the contemporaneity of humans, giant ground sloths and other megafauna in South America.

“Santa Elina challenges mainstream claims on peopling of the Americas, in favor of a model in which people first reached out to the American continent during, or even earlier than, the Last Glacial Maximum,” the authors said.

“It agrees with evidence reported from other sites that suggests early human presence in North America and South America.”

“The Cerutti Mastodon site in California, the United States, stands out as an even more controversial site which has been suggested to present evidence for human presence and megafauna butchery during an interglacial period (around 130,000 years ago), but this evidence has been strongly contested by several scientists.”

The results were published in the Proceedings of the Royal Society B.

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Thais R. Pansani et al. 2023. Evidence of artefacts made of giant sloth bones in central Brazil around the last glacial maximum. Proc. R. Soc. B 29 (2002): 20230316; doi: 10.1098/rspb.2023.0316