The parallel technology argument challenges this model.

If Western Stemmed technology appears in the archaeological record contemporaneously with Clovis technology, and if the two traditions show sufficient technical and morphological differences to suggest independent development rather than one being derived from the other, then the Clovis-first model in its strongest form cannot be correct.

Either there were multiple founding dispersals — with different groups bringing different technological traditions — or the founding population was already technologically diverse before the dispersal into the Americas.

The evidence for parallel development is not confined to Paisley.