Over the past two decades, archaeologists have discovered a number of sites that show that people first arrived in the Americas as early as 16,000 years ago. Some scholars have explored sites that have yielded even earlier dates, but other researchers have questioned the legitimacy of these discoveries, arguing that artifacts recovered from them are not unambiguously the work of human hands. Now, radiocarbon dating of material associated with fossilized human footprints at White Sands National Park has shown that people were living in North America up to 23,000 years ago.

The prints are part of hundreds of fossilized human trackways archaeologists have found at the park that were left in what were once muddy surfaces surrounding an extinct lake. A team including Cornell University archaeologist Tommy Urban identified a series of such trackways, left mainly by teenagers and younger children, that were superimposed on top of each other over the course of millennia. Radiocarbon dating of aquatic plant seeds found below and above six of these trackways shows they were created between 23,000 and 21,000 years ago. “Scholars can question whether a stone or bone artifact was actually shaped by humans,” says Urban, “but there’s no mistaking who made a human footprint.”

While sorting through some 12,000 bone fragments excavated from Contrebandiers Cave near the Atlantic coast of Morocco, archaeologist Emily Hallett of the Max Planck Institute for the Science of Human History noticed that some were smooth and shiny, as if they had been intentionally shaped by human hands. Upon consultation with colleagues, she determined that 62 of the fragments are bone tools dating to between 120,000 and 90,000 years ago. These include a number of tools made from animal rib bones of a type well known for its use in fur and leatherworking. “Once you have an animal skin, there are a lot of steps that have to be taken to process it so it’s supple, smooth, and ready to wear,” says Hallett. “These tools remove the connective tissues and fats from the skin without piercing and damaging it.”

Amid the assemblage, Hallett also identified bones of carnivores such as sand foxes, golden jackals, and wildcats that had marks indicating they had been skinned for their hides or fur. Together, the carnivore bones and bone tools appear to provide the earliest known evidence of people making clothes. This fits well with previous genetic studies of clothing lice that suggested clothing was first worn by humans in Africa up to 170,000 years ago. Hallett says it’s also possible that people at Contrebandiers Cave produced leather to string small beads together to make symbolic personal ornaments. Pierced shells from the snail genus Nassarius dating to around the same time as the bones have also been found in the cave.

Twelve panels depicting images of camels and wild donkeys are now known to be the oldest life-size animal reliefs in the world. By using techniques such as analyzing tool marks and erosion, as well as radiocarbon dating associated artifacts, researchers have dated the reliefs at what is known as the Camel Site to the middle of the sixth millennium B.C.—some 5,000 years earlier than they had originally thought. During the Neolithic period (ca. 8000–3000 B.C.), northern Arabia was much wetter than it is now, and nomads herded sheep, cattle, and goats and hunted abundant wildlife. Animals would have had a crucial role in the herders’ existence, which may help explain why they created the massive reliefs.

Archaeologist Maria Guagnin of the Max Planck Institute for the Science of Human History explains that the site was clearly used for centuries, and possibly even millennia, and new reliefs were periodically added or old ones re-carved when details began to fade. “I wonder if the site was visited regularly, but reliefs were only added on special occasions,” she says. “Or was it only visited for special occasions, when new reliefs were added or existing ones repaired?” Guagnin has no question, however, regarding the mastery displayed by the Neolithic artists, who worked high atop cliffs where they would never have been able to see the entire animal while carving it. “The level of naturalism and detail is astonishing,” she says, “and the technical skill and community effort involved in the creation of these reliefs is evidence of the importance of rock art in the social and symbolic life of the Neolithic herders of northern Arabia.”