Inherited Facial Features
Facial structure is substantially heritable. Twin studies estimate heritability of face morphology in the range of 60–80% for many geometric measurements. This means that family members share facial proportions to a degree that face recognition systems can detect, relatives produce embedding pairs that are closer together than pairs of unrelated individuals, though further apart than same-person pairs.
The degree of embedding similarity correlates with genetic distance: parent-child pairs are more similar than second cousins, which are more similar than unrelated people of the same demographic group. This gradient is not strong enough to make family identification reliable with current systems, but it is statistically detectable in large datasets.
Historical Photo Identification
Genealogists and archivists are increasingly using face recognition to identify individuals in historical photographs. The application is to match unidentified faces in old photos against databases of known individuals. The challenge is that historical photos (particularly pre-1950) have different photographic characteristics, different film grain, different tonal ranges, different geometric distortions from period lenses, that require adaptation to work with modern embedding models.
Commercial genealogy platforms have begun offering face-based search for this purpose, though accuracy on historical photos remains substantially below accuracy on modern photos. Research continues on domain adaptation techniques to bridge the modern-to-historical gap.