Genetic drift — the random changes that accumulate in small, isolated populations — could have altered the distribution of skull shapes independently of selection.

The specific mechanism or combination of mechanisms responsible for the morphological shift between early and late American populations is still an open scientific question.

But the Hoyo Negro findings took one explanation off the table: the morphological shift was not the product of a replacement of one founding population by another.

It happened within a continuous population.

Naia’s haplogroup made that clear.

Twelve Thousand Years Of Changed Ocean