And in the late 1970s and into the 1980s, extraordinary claims about early human presence in the Americas were met with extraordinary skepticism — for reasons that were rooted in a century of contentious debate about when people first arrived in the Western Hemisphere.

The Problem With Spectacular Claims

American archaeology in the twentieth century was not always kind to people who claimed to have found evidence of early human occupation.

The field had been burned too many times by sensational announcements that later failed to hold up to scrutiny.

Sites whose early dates turned out to be the result of contamination.

Objects claimed as human-made tools that turned out to be the products of natural fracture.

Associations between human artifacts and extinct animals that had been disturbed by geological processes and mixed in ways that made the apparent association meaningless.