Mainstream science’s assumption that human habitation of the North American continent began toward the end of the last ice age, about 13,000 years ago, when the ice sheets that covered the northern end of the continent began to recede, allowing humans to cross the Bering land bridge from Asia. Controversial findings from various sites around the Americas suggest an even earlier migration, with humans apparently having been in what is now Florida 14,500 years ago, and in Chile 18,500 years ago. But a new discovery in Southern California may require science to move the generally-accepted date over by a full decimal point, as remains have been unearthed there that have been found to be 130,000 years old.

The scene, found near modern-day San Diego, consisted of the remains of a mastodon that had been killed by having its spine and jaw crushed by a stone tool, with the remaining bones showing signs that they had been harvested for later use. Nearby, the tool in question, a crude stone hammer, was found, matched through flakes from the tool that were found at the hunting site.

The situation took a controversial turn when the results for dating the site came back: the remains were too old for standard radiocarbon dating, so luminescence and uranium dating methods were used instead. The luminescence dating offered the otherwise controversial age of a minimum of 60,000 to 70,000 years, while the more definitive uranium dating came back with something that was considered far more outlandish: the remains were 130,000 years old, give or take 9,000 years.

"It’s quite a claim," exclaims Briana Pobriner, a research scientist with the Smithsonian Institute’s human origins program, although not part of the team that made the find. "The idea that humans in some form were in North America that early is pretty jaw-dropping, but I’m intrigued by the claims the team projected."

The researchers caution that they have no idea as to what species made and used these tools, due to a lack of clues pointing to any individual group. Homo sapiens supposedly hadn’t begun to leave Africa until around 50,000 to 100,000 years ago, along with our closest known cousins, Neanderthals and Denisovans. Homo heidelbergensis, Homo sapiens’ immediate ancestor, began migrating out of Africa 500,000 years ago, but doesn’t appear to have gone much farther than the Middle East and Asia. Could these Middle Paleolithic tool-users have been an even earlier species, such as Homo erectus — or did modern humans get around much earlier than we assume?