The resulting ancient genome — assembled from millions of authentic ancient reads, each contributing a small piece of the puzzle — was then compared to reference genomes from modern and ancient human populations using population genetic methods: principal component analysis, admixture modeling, D-statistics, and other tools for measuring genetic similarity and inferring population relationships.

The entire process, from sample to insight, takes months.

It requires specialized equipment, specialized expertise, and computational resources that did not exist even a decade before the Yana study was published.

It is, in its technical sophistication, one of the more demanding scientific undertakings that modern biology has produced.

And at the end of it, the result was a population that no one had known existed: the Ancient North Siberians, revealed in the genomes of two children who had lived 31,000 years ago above the Arctic Circle and left their baby teeth behind in the frozen sediment of the Yana River terrace.

The Unanswered Question — Where They Went