They were neither the ancestral East Asian populations from whom most of the rest of northeastern Siberia’s prehistoric inhabitants would be derived, nor closely related to the ancient populations of Europe and western Eurasia.

Professor Laurent Excoffier of the University of Bern, one of the study’s authors, described it this way: “Remarkably, the Ancient North Siberians people are more closely related to Europeans than Asians and seem to have migrated all the way from Western Eurasia soon after the divergence between Europeans and Asians.”

This is a striking finding that requires some unpacking.

The branching of the human family tree — the sequence of population splits and divergences that produced the distinct genetic profiles of the world’s major population groups — happened over tens of thousands of years after the initial expansion of modern humans out of Africa.

When the ancestors of today’s East Asians and the ancestors of today’s Europeans diverged from each other, that divergence happened roughly 40,000 years ago or so.