Were they the mammoth-hunting Clovis people who lived 13,000 years ago, or some earlier group who archaeologists are just beginning to understand?
A recent discovery in the Oregon desert announced in the April 4 edition of Science may end the debate once and for all.
For the last two decades, the "Clovis-first" idea has been under steady assault.
Call it revisionist prehistory: researchers have turned up evidence they say supports everything from a much earlier migration from Asia to a sea-borne invasion from Europe.
The coprolites Jenkins found in the Paisley caves may well be the final nail in Clovis' coffin.
While other supposed pre-Clovis sites have been bogged down in arguments over whether stone tools were made by people or by accident, there's no doubt who made the coprolites Jenkins found in the Paisley cave.
"To be honest, I didn't think they would be that interesting." Eske Willerslev in his University of Copenhagen lab.
Sequencing ancient DNA requires tightly controlled conditions to prevent contamination.
The Dane wanted to know how old the Paisley coprolites were.In a study published April 4 in the journal Science, Jenkins and University of Copenhagen geneticist Eske Willerslev argue that the artifacts were made by the ancestors of modern Native Americans, then deliberately left behind in southern Oregon's Paisley Caves.