Claes, Peter, et al. “Modeling 3D Facial Shape from DNA.” PLoS genetics 10.3 (2014): e1004224.

A few weeks ago a paper came out in PLoS GENETICS, Modeling 3D Facial Shape from DNA, which attempts to push the ball forward when it comes to mapping complex traits like facial morphology from genetic data. The long term goal here is clear: to forensically infer one’s phenotype purely from genetic information. For simple quasi-Mendelian traits like blue vs. brown eye color difference this is already possible with a high degree of certainty (or at least far higher than eyewitness reports) because much of the trait variation is controlled by one or a few genes. But for complex traits like height where variance is distributed across thousands of loci this is not feasible because the understanding of the genetic architecture is far more primitive and incomplete. The most explanatory height loci are on the order of ~1 percent of the variance of the trait in a population. In contrast blue vs. brown eye color variance within Europeans has a ~75 percent explanatory proportion at the HERC2-OCA2 locus.

The technical details of how they modeled facial morphology is rather interesting, but I’m not going to focus on that (they zeroed in on a mixed-race population to maximize phenotypic and genotypic variance). Rather, note that the authors can now relate phenotype and genotype very precisely on a population wide basis. In the past you would have to look at someone and assess their racial background or sex status. But today genetics can give you a very precise estimate of their racial ancestry, or an accurate prediction of their biological sex. The correlations are good, but observe that there are deviations from a strict association. These are perhaps just as interesting over the long term.

When it come to the domain of sociology and culture there are many models of how your physical appearance impacts how others perceive you, and how you develop as a person. You can see in the chart that there are many people who have more African ancestry, but less African features, than other sets of people (Rashida Jones and Joakim Noah likely fall into this class of pairs; Rashida Jones’ father is 66% African in ancestry, while Noah’s is 50%, so she is likely to have more African ancestry, despite having more European facial features by most accounts). By looking at these deviations from expectation you can actually test the power of genetics vs. sociology. In the case of the Duffy antigen trait clearly genetics will be determinative. On the other hand there are all sorts of medical (e.g., hypertension) and behavioral (e.g., intelligence test scores) differences between the socially understood black and white American populations where looking at individuals who vary in genotype and phenotype might illuminate the weight of the variables.

And I’m not talking rocket science here. Within 10 years surely much research will have been done in this area simply by looking at numerous genetic data sets, and combining them with phenotypic information. If scientists don’t do it, I suspect marketing and credit rating firms will, because they already have huge piles of data on most Americans (i.e., phenotypes, or instrumental variables to infer phenotypes). And this does not apply to just race. Though the difference between male and female faces is striking, there is some overlap there as well. Questions could be asked about the outcomes of men and women conditional on their facial morphology. The existence of AIS individuals would be another dimension to explore.