The timing of this migration has been one of the most contested questions in American prehistory.

The oldest well-established human presence in the Americas was once thought to date to roughly 13,000 years before present, associated with the Clovis culture — people who left distinctive fluted stone spear points at sites scattered across North America.

But evidence for pre-Clovis human presence has accumulated over the past several decades, with sites in Chile, Oregon, and New Mexico now providing robust evidence for people in the Americas as early as 14,500 to 23,000 years ago or even earlier, depending on the site and the analysis.

The ancient DNA record has added crucial dimensions to this story.