During the Beringian standstill, the ancestral Native American population would have been evolving in relative isolation from the other Asian populations from which it had derived.

The specific genetic diversity of the founding population — including whatever ancestral structure related to Population Y it may have contained — would have been the product of this isolated period of evolution, plus the specific admixture history that preceded the formation of the Beringian population.

The timing and nature of the Beringian standstill has implications for how Population Y should be interpreted.

If the standstill was long enough for significant internal differentiation to occur within the isolated founding population — for distinct subgroups or lineages to form with somewhat different genetic profiles — then the differential distribution of those lineages across the Americas could produce patterns of allele sharing that look like separate migrations when analyzed with certain statistical tools.