This migration was in the interglacial ages.
Also, for the really "open minded" - explain this: Horses and the Camelids all evolved in North America; Camels in Asia have been domesticated for at least 10,000 years, Horses for at least the last 7500. Mongolian horses are roughly 15,000 years behind in evolution to modern horses, but exist at the same time. Statues of tall white men, with blond hair, have been found in northern Peru, that were mistakenly dated at 2500 years old, but are really closer to 8000 years old, they were found with animal statues dismissed as stylized llamas but on closer inspection appear to be camels.
Now draw your migration maps, and something becomes very clear.
OTOH: read "The Last Giant Of Beringia"
See the article linked in post #56.
I read something of that nature. I would not be surprised if early Americans bought camels and horses to Asia and Europe. American Indian gene has been found in Europe and Asia. Some American Indians have genes similar to Basques, Celts, and Berbers, among them Mapuche, Inca, and Mayans. The Anasazi have some relics that look Celtic like.