Early humans living in South America carved giant sloth bones into decorative ornaments that may have been used as jewelry. The discovery also provides new evidence that people arrived in central Brazil during or before the end of the last ice age.
Giant sloths, larger than polar bears and armed with bony plates, once roamed South America during the Pleistocene Epoch, also called the ice age. Climate warming and hunting by people drove ground sloths to extinction around 10,000 years ago, and some of their remains are preserved in human-inhabited caves, including the Santa Elina rock shelter in Brazil.
Although the skeletons of giant sloths are largely degraded, thousands of their fossilized bony dermal plates, called osteoderms, remain as fossils. Three of these scale-like bones, which are between 16,000 and 27,000 years old, have puzzled scientists for decades because of their unusual shape and smooth texture. The bones had full or partial holes drilled near the edge as if they were going to be strung on a string.
Archaeologists had speculated that the giant sloth’s bones were modified by humans using stone tools, he says. Mirian Pacheco at the Federal University of São Carlos in Brazil, “but the big question is, were those artifacts made by humans during the coexistence of humans and [giants sloths]?”
To find out, Pacheco and his colleagues examined the bones using high-resolution microscopes and X-rays. Their analysis revealed scratches in different directions and repeated indentations made by early stone tools. The shape and texture of the bones could not be explained by natural erosion or animal bites.
The bones formed before they fossilized, suggesting that humans arrived in the Americas before the end of the ice age. “It’s really exciting to have this window into how people in the past interacted with these species that we no longer have,” he says. Alexis Mychajliw at Middlebury College in Vermont, who was not involved in the work.
The smoothness of the bones suggests repeated friction, possibly from being worn daily as personal adornment. If so, this is some of the first evidence of personal artifacts in the Americas, but more research is needed to determine its significance.
“It would be interesting to see if [used these bones] for decoration, for fashion, or to show that they belonged to a specific group”, says Thais Pansani, part of the team. “But we definitely know they were using them.”