He walks through the ice free corridor theory, the longstanding model for how humans first entered the Americas. As the Laurentide and Cordilleran ice sheets retreated, a passageway opened between them, theoretically allowing migration from Beringia down into the Great Plains around thirteen to fourteen thousand years ago. For decades, this corridor was treated as the only viable route. But the evidence has shifted. Coastal routes, pre-Clovis sites, and the timing of ice melt have all challenged the idea that this corridor was the primary gateway. The question isn't whether it existed, it's whether it was open early enough and hospitable enough to support the migration timeline we've been taught.