The traditional Clovis-first model held that the movement of people from Asia into North America was constrained by the ice — that the glaciers blocked southward passage until an ice-free corridor opened around 14,000 to 15,000 years ago.

But 23,000 years ago, that corridor did not exist.

The glaciers were expanding, not retreating.

The path that would eventually open through the interior of the continent was not available.

If people were in New Mexico 23,000 years ago, they could not have arrived via an ice-free interior corridor that did not yet exist.

They must have arrived earlier, by a different route, or both.