The increasing density of ancient genome data from across the Americas is helping to clarify this picture.

By comparing ancient genomes from different time periods in the same geographic area, researchers can track the specific timing of population changes and can distinguish between changes that occurred before and after the periods when the Population Y signal first appears in the record.

One of the most important findings of this kind of temporal analysis is that the Population Y signal, where it is found in ancient specimens, appears to be present in the earliest individuals from certain regions rather than appearing later in the record as a new introduction would be expected to do.

This is consistent with the deep ancestral structure model — the signal was there from the beginning because it was part of the ancestry of the founding population — and less consistent with models that require a separate, later migration to introduce the Australasian-related ancestry.