Monte Verde in the 1970s and 1980s, Meadowcroft Rockshelter and its controversial dates, the Paisley Caves, the Friedkin site in Texas, and numerous other sites each contributed a piece of evidence that pointed in the same direction: people had been in the Americas before Clovis, and they had been there for considerably longer than the standard model allowed.

But the pre-Clovis claims were often met with skepticism — sometimes legitimate methodological skepticism, sometimes what critics characterized as a systematic reluctance to abandon the Clovis-first framework.

The bar for evidence of pre-Clovis occupation was set very high, and different researchers set it at different levels.

What one group of researchers considered compelling evidence of pre-Clovis presence, another dismissed as ambiguous or contaminated.

White Sands entered this debate with several advantages over many previous pre-Clovis claims.

The evidence was not stone tools, which can be ambiguous — human-made or naturally fractured, the debates over some claimed pre-Clovis tools have lasted decades.