For decades, the Clovis-first hypothesis held that Clovis people were the first Americans — that they had crossed from northeastern Asia into Alaska via the Bering land bridge when low sea levels connected the two continents during the Ice Age, then moved south through a corridor between the retreating Laurentide and Cordilleran ice sheets as the glaciers began to retreat around 14,000 to 15,000 years ago.

The model was elegant and had genuine evidential support.

The Bering land bridge was real — it is documented by geology.

The ice-free corridor was real — it opened as the glaciers retreated.

Clovis technology spread across the continent rapidly and appeared at broadly similar times across a wide geographic range, which was consistent with a relatively rapid southward expansion of the first arrivals.

And for much of the twentieth century, no site with convincing evidence of pre-Clovis human occupation had been accepted by the archaeological mainstream.