Before going further into the specific findings, it is worth pausing to explain, in plain terms, what the genetic analyses are actually measuring when they report “affinity” or “allele sharing” between ancient South Americans and Australasian populations.

This is one of the most commonly misunderstood aspects of the Population Y story, and the misunderstanding tends to produce dramatically oversimplified headlines.

Alleles are the different versions of a gene — or more broadly, the different variants of a specific position in the genome — that exist in a population.

Every human being inherits two copies of each chromosome (one from each parent), and at any given position in the genome, those two copies may carry the same variant (if both parents passed on the same version) or different variants.

Across the three billion or so positions in the human genome, the specific combination of variants that an individual carries is their genotype.