Key Points Key Points Researchers found human-modified giant sloth bones dating to 25,000–27,000 years ago in Brazil, potentially pushing back South America’s earliest human presence by 12,000 years. Scientists used advanced microscopy and scanning techniques to argue that perforations in sloth bones were deliberately drilled by humans and worn as pendants. Figuring out when exactly humans first reached South America increasingly depends on how you—read the bones of a giant ground sloth? There, researchers reported the presence of human-modified giant sloth bones (osteoderms) found alongside stone artifacts in a layer dated to roughly 25,000–27,000 years ago. “In this scenario, Late Pleistocene sites containing evidence of early human occupation in South America should be closely scrutinized with interest.”