I guess I, and others, are guilty of rambling around a few topics (

) here.
But there seems so little we really know about ancient, and even relatively modern, Amerindians.
It is hard to divide them into N and South now, with the new archaeology -movement
may have been both ways.
It is also an area where new stuff, and fascinating, iconoclastic books (like
1491) keep popping up every other day.
PS
1491
has a chapter on the various academic arguments around this topic.
i am not sure if I completely followed it, as I have not studied any American History.