First, the age: approximately 11,500 years before the present places USR1 in the critical period when the founding population of the Americas was still in the early stages of its geographic expansion and genetic diversification.

Genomes from this period capture the founding diversity before it was diluted by subsequent migration, admixture, and population processes.

Second, the location: interior Alaska is closer to the Beringian source region than almost any other location in North America, making it the most likely place to find representatives of the earliest and most deeply rooted branches of the Native American founding population.

Third, the genetic position: the basal relationship of USR1’s lineage to all other sampled Native American populations means that she provides information about the founding population at its deepest sampled level.