I struggle with this question...often. I don't know.
http://www.google.com/search?num=100&hl=en&lr=&rls=GGLG%2CGGLG%3A2006-22%2CGGLG%3Aen&q=Gm+blood+type++ainu
A few sites say Ainu have a Mongolian blood type called Gm. Therefor cannot be Caucasian. Not enough citations in my opinion