The specific route — the Bering land bridge — was well-established geologically.

The genetic relationship was confirmed by multiple types of analysis.

The question of when, and in how many waves, had been actively debated.

But the basic directional claim — East Asia to Beringia to the Americas — seemed well-founded.

What the MA-1 analysis revealed was that this picture was incomplete.

The East Asian ancestry in Native American genomes was real, but it was only part of the story.

There was another component — the Ancient North Eurasian component — that had been sitting as an unexplained residual in population genetic models.