I agree there's lots of speculation regarding this issue, but no hard evidence. Did you see the PBS program about the skeletal remains unearthed (in New Hampshire?) that differed significantly from American Indians (forgive me if I have that term incorrect) physiologically? There is a law that requires burial of Indian remains ASAP so the scientists could not conclude their study, but the buzz was the age of the bones indicated they did not belong to the same strain of humans as American Indians. Interesting.