Admixture is another possibility, and perhaps a more likely one.

As Northern Native American populations expanded into areas where Ancient Beringians lived, intermarriage between the two groups would have been the expected outcome of prolonged coexistence.

The result of extensive admixture would be a gradual blending of the two ancestries, with Ancient Beringian ancestry becoming increasingly diluted over generations as it mixed with the numerically dominant Northern Native American ancestry.

After enough generations of admixture, Ancient Beringian ancestry might persist at very low levels in descendent populations — too low to be easily detected against the background of Northern Native American ancestry in genome-wide analyses.