But the consensus was already under serious pressure before White Sands.

Monte Verde, a site in southern Chile excavated by archaeologist Tom Dillehay and his colleagues beginning in the 1970s, preserved organic material — wooden structures, plant foods, animal remains — that was dated to approximately 14,500 to 15,000 years ago.

The site eventually received mainstream acceptance in the late 1990s, after years of skepticism and debate, as evidence of pre-Clovis human presence.

But its location was the problem it created, not solved: Monte Verde is in southern South America, more than 10,000 miles from the Bering Strait.

If people were there 15,000 years ago, they had to have been somewhere farther north considerably earlier — but where was the evidence of that earlier northern presence?

The Paisley Caves in Oregon contained human coprolites — preserved ancient feces — that yielded DNA and radiocarbon dates suggesting human presence approximately 14,000 to 14,500 years ago, slightly predating or contemporaneous with the earliest Clovis sites and again suggesting people were in the interior of the continent earlier than the standard model comfortably accommodated.