It was a strong inference, not an absolute certainty.

Eye color and hair color and texture operate similarly — determined by multiple genetic variants that can be analyzed from a genome to produce probabilistic predictions.

Beyond physical characteristics, the genome carries information about ancestry.

Specific patterns of genetic variation — specific combinations of variants found at specific frequencies — are characteristic of different population groups with different histories.

By comparing an ancient genome to reference databases of modern and ancient genomes, researchers can determine which population group the ancient individual is most closely related to, and what that relationship implies about migration and population history.

Opening The Genome