Artifacts at this site may predate Clovis by 3,000 years or more, but these conclusions are disputed. The primary excavation has gone down to a level that dates to at least 50,000 B.C.E., searching for evidence of cultural artifacts. Until increasing challenges in the first decade of the 21st century to the Clovis theory based on this site and others, it was unusual for archaeologists to dig deeper than the layer of the Clovis culture, as they then believed that no human artifacts would be found older than Clovis. Among the objects from the "pre-Clovis" stratum, dated to 16,000-20,000 years BP, is a large piece of rock nicknamed the "Topper Chopper." This apparent tool offers some of the most compelling evidence for human agency, including bifacial flaking of the edge.