February 18, 2009

Estimating degree of Native American admixture from faces

Klimentidis and Shriver have a new paper which looked at the concordance between people's perception of Native American admixture and their actual admixture estimated from ancestry informative markers. Overall, observers' ratings were non-random, indicating that they could indeed estimate ancestry from facial appearance. They were, however, closer to random than to the actual admixture proportion, indicating a great degree of "noise" in the estimate. Interestingly, Europeans estimated admixture more accurately than Native Americans, although they tended to overestimate it, while Native Americans tended to underestimate it.

Some related posts on appearance-ancestry correlations from the Shriver lab.

PLoS ONE doi:10.1371/journal.pone.0004460

Estimating Genetic Ancestry Proportions from Faces

Yann C. Klimentidis, Mark D. Shriver


Ethnicity can be a means by which people identify themselves and others. This type of identification mediates many kinds of social interactions and may reflect adaptations to a long history of group living in humans. Recent admixture in the US between groups from different continents, and the historically strong emphasis on phenotypic differences between members of these groups, presents an opportunity to examine the degree of concordance between estimates of group membership based on genetic markers and on visually-based estimates of facial features. We first measured the degree of Native American, European, African and East Asian genetic admixture in a sample of 14 self-identified Hispanic individuals, chosen to cover a broad range of Native American and European genetic admixture proportions. We showed frontal and side-view photographs of the 14 individuals to 241 subjects living in New Mexico, and asked them to estimate the degree of NA admixture for each individual. We assess the overall concordance for each observer based on an aggregated measure of the difference between the observer and the genetic estimates. We find that observers reach a significantly higher degree of concordance than expected by chance, and that the degree of concordance as well as the direction of the discrepancy in estimates differs based on the ethnicity of the observer, but not on the observers' age or sex. This study highlights the potentially high degree of discordance between physical appearance and genetic measures of ethnicity, as well as how perceptions of ethnic affiliation are context-specific. We compare our findings to those of previous studies and discuss their implications.



n/a said...

Keep in mind that Shriver's admixture estimates are themselves full of noise; ABD also tends to overstate minor and non-existent admixture. I would prefer to see observer estimates compared to estimates from more accurate genetic tests.

Jack said...

People's percepition... which means that if not visible from looking at the face or head then people cannot guess correctly. This may explain part of the randomness.
Also I noticed that many white americans tend to consider normal white faces the faces that to a native west european look slightly exotic or asian.

Onur Dincer said...

Also I noticed that many white americans tend to consider normal white faces the faces that to a native west european look slightly exotic or asian.

What do you mean? Slightly exotics the normal ones? Or just a portion of them?