Not here. During the Ice Age, this land was ice-free just as now. Permafrost, muskeg, sabertooth, mammoth, muskox all still here, although the sabretooth and mammoth are subsurface now. It's the same, and you don't go far on foot in the summer. In the winter the Yukon River is a 12-lane superhighway. 12 thousand years ago the land route south was blocked. Still is, except for that gov't road.