Giant ground sloth pendants show humans were in South America 25,000 years ago

Three pendants made from the bones of the extinct giant ground sloth represent the oldest evidence of humans living in South America, dating back 25,000 years.

Determining when humans first arrived in the Americas continues to be the subject of intense debate and controversy. Scepticism persists in scientific circles about whether humans made it to the Americas before 16,000 years ago.

The artefacts, found in Santa Elina rock shelter in central Brazil, add to growing evidence for human occupation in South America much earlier than previously thought. A 2013 study of human-made objects in another Brazilian cave, Toca da Tira Peia, were dated to 22,000 years ago.

The latest finds are described in a paper published in the Proceedings of the Royal Society B.

The small trinkets were made from osteoderms, literally meaning “bone skin.” These bony deposits are found within the skin of some animals, including crocodiles, dinosaurs and a few mammals like armadillos. It is believed that the primary use of osteoderms is to act like in-built armour.

Giant ground sloths, Glossotherium phoenesis, grew to about 4 metres long and would have weighed up to 1,700 kilograms. Due to their size and strength, these animals would have had few natural enemies. Only the South American short-faced bear Arctotherium and South America’s famous sabre-toothed cats such as Smilodon would have had the power to bring a Glossotherium down.

They were once common in Brazil and other parts of South America anddied out about 10,000 years ago.

The osteoderms discovered in Santa Elina possessed small holes that could only have been produced by human hands.

Located in Brazilian state Mato Grosso, the Santa Elina rock shelter has been studied by archaeologists since 1985. More than a thousand figures are drawn on the cave walls. Hundreds of stone tools and thousands of sloth osteoderms have been found at the site.

But three of them bear what appears to be mark of human drill holes. The scientists used various techniques including UV and visible photoluminescence to test whether the holes could have been produced by rodent bite marks. There results suggest that the holes were drilled by humans.

Using radiocarbon, uranium-thorium and optical stimulated luminescence dating techniques, the researchers conclude that the layer in which he osteoderms were found is 25,000 to 27,000 years old.

While the cultural significance of the artefacts remains a mystery, the authors say their findings prove the existence of humans in South America before the Last Glacial Maximum – the coldest part of the last Ice Age – 21,000 years ago.

“Our evidence reinforces the interpretation that our colleagues working on Santa Elina have been talking about for 30 years,” first author Thaís Pansani, a paleontologist at the Federal University of São Carlos in Brazil is reported to have said in an email to Live Science. “Humans were in Central Brazil at least 27,000 years ago.”