Thank you for your post. The fact that the ancestors of long-headed (dolichocephalic) Ainu may have contributed to the European gene pool at some period should not lead modern Europeans to claim such people as found at Kennewick were “Caucasoid” Europeans who remain a predominantly mesocephalic and brachycephalic (broad-headed) population. This is the problem with present DNA analysis and European “scholarship” in general. They don’t use their heads!!
Welcome to Free Republic.
Most Europeans are of the R1 DNA line (R1a & R1b) and I believe the Ainu are descended from the branch that split and became the R2 line.(68% of Europeans are R1b)
Btw, it looks like haplogroup X arrived at Meadowcroft about 25,000 years ago.