One was that there had been a separate migration to the Americas by a population related to Australasians — a second wave of dispersal from Asia that arrived in the Americas after the main Beringian founding population but before significant mixing between the two groups.

Another was that the signal reflected deep ancestral structure within the Asian populations that gave rise to Native Americans — that the ancestral Beringian population itself contained distinct subgroups, one of which was more closely related to Australasian populations than the other, and that this internal diversity was preserved in different proportions in different descendant populations.

The 2015 paper’s authors acknowledged that distinguishing between these models would require additional data — specifically, ancient genomes from the relevant time periods and geographic regions — and that the current data were consistent with multiple explanations.

They were, in other words, appropriately cautious about what the finding meant while being clear that the finding itself was robust.