Proof of Advanced Civilization 500,000 Years Ago?
Other challenges to the hypothesis include an apparent lack of Solutrean-style artwork (like that found at Altamira in Spain and Lascaux in France) among the Clovis people. In response, proponents point out that this style of art disappears in Europe by the time of Clovis, and that the Solutreans introduced a tool-making innovation and not necessarily cultural or artistic practices.
1) Even if Solutrean points are identical to Clovis points, that proves only that there was contact between the two groups. Perhaps a boatload of Solutreans came to America and taught the people already there how to make the points. If these points were truly innovative, they could've spread across the continent quickly.
Again, all this would've required was initial contact between a handful of Solutrean and Clovis people. To prove that the Solutreans colonized the "New World" in force, you'd need evidence of a large-scale migration: bones, DNA, artifacts, campsites, etc.
2) Scientists increasingly believe that the Clovis people weren't the first Native people to arrive here. As Charles Petit wrote in 1998:
Ironically, the Petit article also quotes Dennis Stanford, who conceived the Solutrean hypothesis:
For more on the subject, see Kennewick Man, Captain Picard, and Political Correctness.