Wow....1200.
That was even before I was born...I think.
This is a great subject of study, and I look forward to reading more. The dynamics of early tribal peoples here are something we hear very little of, and I have always wondered about.
Great stuff.
Actually, there is a lot written about the dynamics of early tribal peoples, but most of appears to be supposition. But the general feeling that I get from the literature in the field is that the various tribal groups were not as isolated as we are generally led to believe. I remember visiting the Pueblo Grande museum some time ago and being shown evidence that the Hohokam peoples in the valley of the sun (phx metro area) traded quite regularly with the meso-americans. This sort of blew me away, because of the (then) controversial assertions by a few archaelogists some years ago that the Aztecs originated in New Mexico.