A gradual process of admixture, during which Checua-related ancestry was progressively diluted as new populations arrived, would eventually produce a signal below detection thresholds without requiring every biological descendant to die without reproducing.

The genetic detection threshold matters.

When researchers describe ancestry as “not detectable,” they mean not detectable at the statistical level of their analysis.

Small amounts of ancestry from a distant source — ancestry that has been diluted across many generations of admixture — can fall below detection thresholds even when it technically persists in the genomes of living populations.

None of this undermines the core finding that the Checua genetic signature underwent a dramatic transition between 6,000 and 2,000 years before present.

The finding is real and significant.