The land bridge that once connected North America and Asia rose from the seas 80,000 years ago. And at the same time, North America's climate began experiencing violent climate swings, with average temperatures shifting as much as ten degrees every decade.
That pattern of massive temperature swings lasted a whopping 70,000 years, which just so happens to be pretty much the exact same time period the land bridge connected Alaska and Siberia. Known as Beringia, this bridge was really its own vast landmass, a thousand miles across in places and home to its own relatively comfortable ecological refuge. We know animals used Beringia to move between the two continents, and although there's now evidence to suggest humans actually used coastal boats to reach the Americas, it's likely Beringia played a role in human colonization of the Americas.