If Clovis culture were different to their forebears, for reasons other than ecology or technology, that could be evidence of isolationism.
However diffusion and re-invention are not the only explanations for culture. Nature and life sustain narrowly defined repertoires. So does culture. Thus nature and culture are archetypal. Just add people and the full repertoire of culture, with all its media, crafts, and attempts at science, re-emerge. The few inherited and borrowed stylistic features should not distract us from the study of the core content of culture. Then we could know ourselves. See some of the links I have posted in comments above.
Edited 1 time(s). Last edit at 24-Apr-18 11:07 by Edmond.