As time and research goes on, we will find that the story of how homo sapiens populated the different continents and areas is much more complicated and full of lots more different twists and turns that we now imagine.
For example, Professor Oppenheimer's DNA research noted in post #6 above, places people of European ancenstry closer in genetic lineage to American Indians than to any other group.
The reason is that most of the group that originally populated Europe moved in from the East from an area north of the Caspian Sea which is also an origination point for most of the group of people that moved into North America and became the Indians.
Of course over 1,000's of years, there is some genetic drift and lots of interbreeding with other people along the way but the DNA is still closest between these two groups.
Hmm... I remember reading somewhere that the triangle between the lakes Van-Sevan-Urmia [SW from the Caspian, not N of it] was the cradle of the Indo-European language group of people. They tried to trace cognate words and figured out that the place needed to have birches, beech, snow [occasionally], salmonids and so on. That sort of meshed with counterclockwise centrifugal dispersion from there, traceable by other means.