Others found weaker or less statistically clear signals.

The results depended on which reference populations were used in the comparison, which statistical methods were applied, and which specific ancient individuals were included in the analysis.

This variability in the results was itself informative — it suggested that the Population Y signal, whatever its ultimate cause, was not a uniform feature of all early South Americans, was sensitive to the specific analytical choices made by researchers, and required more data and more careful analysis than the 2015 study had been able to bring to bear.

The 2018 studies also contributed a new layer of evidence relevant to a specific question: had the people of Lagoa Santa contributed ancestry to later South American populations?