As predicted, the researchers found that facial traits are much more variable than other bodily traits, such as the length of the hand, and that facial traits are independent of other facial traits, unlike most body measures.
Other issues can be identified in the process of constructing and measuring facial traits.
Furthermore, most classical studies adopted facial traits derived from two-dimensional distances between landmark pairs16,17,18,19,20,21,22,23,24,25,28,29.
Nevertheless, heritability estimates of facial traits have often been surprisingly low or difficult to replicate.
Ten facial traits derived from Euclidean distances (EDTs) between selected landmark pairs were subsequently considered.
In addition, using a smaller set of these landmarks, we explored the heritability of more traditional distance-based facial traits.
Although both dynamic (i.e., facial expressions) and static facial traits are used as cues of altruism, only static facial traits have been shown to be cross-culturally readable with respect to altruism detection skills.
We also explored the heritability of facial traits based on Euclidean distances (EDTs), as well as equivalent phenotypes measured using Geodesic distances on the facial surfaces (GDTs).
For facial traits in particular, it may be expected that gender also plays a role in shaping up the facial characteristics we study, such as curvature measures.
We examined whether the use of facial traits derived from Geodesic distances (GDTs), only possible on 3D data, yielded any advantages compared to Euclidean traits.
