When researchers analyze the genomes of a large set of populations and construct a statistical tree showing how they are related, some populations sit close to the trunk — they branched off early, before the other populations had diverged from each other.

These early-branching populations are described as basal to the later ones.

They share ancestry with all other populations in the tree, but they share their most recent common ancestry with a broad, early ancestor rather than with any specific later group.

The Checua individuals occupy this basal position relative to other ancient South American populations in the researchers’ comparison set.

Their genomes contain the signal of early South American ancestry — they share the broad foundation that connects all Native American populations, ultimately traceable back through the founding migrations from Asia.