Peter Frost has a new theory of human migration. About 40,000 years ago, humans were in the Middle East. From there, some moved west (to the Mediterranean) and others moved east (to India and Sahul). None could move north, though, because of the Ice Age cold. Between about 40,000 and 30,000 years ago, the Mediterranean population was blocked from further spreading north into Europe or beyond because of the harsh conditions of the steppe-tundra running from SW France through to Asia.
But then some adapted and spread like wildfire.
Sometime after 28,000 BP, they broke out from the beachhead and colonized the tundra plains in their entirety.
After the breakout, nothing could stop them from spreading east throughout the Eurasian steppe-tundra … all the way to the Pacific Ocean, and from there to Beringia and North America. They would in time become the ancestors of most people living today, not only Europeans but also East Asians and Amerindians.
The initial colonizers are called Gravettians and their main adaptation was to master reindeer and mammoth hunting. This group, Frost proposes, was ancestral to Europeans and East Asians and Amerindians and such groups as the Saami of Lapland and the Ainu of Japan.
This hypothesis may account for a pair of puzzles.
First, there is the puzzle of the oft-noted similarity in appearance between West Eurasians and Ainu, the indigenous people of Japan.
Second, there is the puzzling similarity between Solutrean (from France, 20,000 years ago) and Clovis (Amerindian, 15,000 years ago) spear points. It seems a far better explanation than having the Solutreans sailing through the Ice Age North Atlantic.