Archaeological evidence establishes that Indigenous peoples were present in the Americas at least 15,000 years ago. Scientists don’t agree, however, on when people first arrived. Some archaeologists claim it must have been much, much farther back, citing evidence such as flaked stones in layers dating to ~30,000 years ago at the Chiquihuite Cave site in Mexico, bones with cut marks in layers dating to 34,000 years ago in Uruguay, flaked stones in layers dating to 30,000-50,000 years ago in Brazil, and even broken mastodon bones dating to 130,000 years ago in California. All of these claims are heavily disputed.
As a rule, an archaeological site won’t gain widespread acceptance as legitimate unless there is clear evidence of human activity, that evidence can be securely dated, and it is found in an undisturbed geological context. For example, a hearth containing the remains of charred animal bone fragments and stone tool fragments at the Dry Creek site in Eastern Beringia (near the present-day Denali National Park in Alaska) was dated to 13,485-13,365 years ago from wood charcoal pieces taken from within the hearth. The stone tools – resharpened blades, flakes, end scrapers, and the byproducts of manufacturing them – and repeated controlled fires used to cook animal bones clearly indicate a human presence. The intact stratigraphy and multiple independent radiocarbon dates from the hearth tell us when people were using this particular part of the site. To archaeologists, this is uncontroversial. In contrast to the Dry Creek site, there is no consensus that the very early sites discussed above have met that standard; critics argue that the stone ‘artefacts’ and ‘butchering’ marks could be the result of natural phenomena (or even, in some cases, left by modern construction equipment). There simply hasn’t been any uncontroversial physical evidence of a human presence in the Americas more than 15,500 years ago.
Then, in 2021, a team of archaeologists dropped a bombshell into this debate: they’d found footprints – unquestionable evidence of a human presence – at White Sands National Park in New Mexico, dating to between 23,000-21,000 years ago.
The White Sands Locality 2 site was once the shore of an ancient lake. For more than 2,000 years, humans and animals visited it. As they walked along the muddy surface, their feet mushed tiny seeds of ditch grass into the ground, leaving a vital organic trace that archaeologists can use for carbon dating. (Some archaeologists have criticised the dating methods used, but there is general agreement that the presence of human tracks with fauna known to have gone extinct around 11,000 years ago dates these to – at minimum – the end of the Pleistocene.) If the find holds up to scrutiny, physical evidence of a human presence in the Americas during the LGM would be a paradigm-changing event, pushing back the date of the earliest migrations to sometime before 25,000 years ago.