The mainstream of American archaeology in the late 1970s and 1980s was not ready to accept the Manis evidence.

The objections were real — the original radiocarbon dates were not as precise as AMS dating would later provide, and the embedded fragments had not been fully characterized — but they were sometimes stated with more certainty than the state of the science warranted.

The Clovis-first framework was still dominant, and Manis was too ambiguous, too fragmentary in its evidence, and too far outside the accepted timeline to win easy acceptance.

Gustafson continued to advocate for the site’s importance.