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June 26, 2005

Eurasian faces....

This Sydney Morning Herald piece summarizes a paper that asserts that:

...In experiment 1, Caucasian participants rated own-race composites as more attractive than other-race composites, but only for male faces. However, mixed-race (Caucasian/Japanese) composites were significantly more attractive than own-race composites, particularly for the opposite sex. In experiment 2, Caucasian and Japanese participants living in Australia and Japan, respectively, selected the most attractive face from a continuum with exaggerated Caucasian characteristics at one end and exaggerated Japanese characteristics at the other, with intervening images including a Caucasian averaged composite, a mixed-race averaged composite, and a Japanese averaged composite. The most attractive face was, again, a mixed-race composite, for both Caucasian and Japanese participants. In experiment 3, Caucasian participants rated individual Eurasian faces as significantly more attractive than either Caucasian or Asian faces.

If you read the full paper (23 pages of PDF, if you don't have access to this paper use this link) you will note that they recruited Eurasian individuals for these experiments, that is, a real population instead of just a hypothetical composite created from the Asian and Caucasian test subjects.

The authors suggest that "attractiveness" (in this case for "average" face composites) is not based on "prototypical" features since Caucasians and Asians preferred Eurasian faces, which would not be "prototypical" of their own population. Instead, they posit that "health" is being signalled. It all seems a bit thin to me, and the authors admit that preference for "Eurasians" could not have evolved in any EEA, since by definition Asians and Caucasians would have been shaped by selection forces in a different environment and population. As for the argument about heterozygosity...my impression is that biologists have had a hard time finding genuine heterozygote advantage in the natural world.1 Of course, Armand Leroi has recently been contending that interracial individuals will mask deleterious recessive traits, but that presupposes a high level of genetic load in the source populations. At this point, I think we should look to the flies and mice before assuming too much about humans.2

Update: Hm...well, I was pointed to this paper that argues that males who are heterozygous on MHC loci are more facially attractive than not:

...Here, we show that heterozygosity at three key loci in the major histocompatibility complex (MHC) is associated with facial attractiveness: Faces of men who are heterozygous at all three loci are judged more attractive by women than faces of men who are homozygous at one or more of these loci. MHC genes code for proteins involved in immune response....
This is very suggestive, though past research has offered conflicting results on female preference of MHC profiles.3 I stated earlier that there haven't been enough finds of heterozygote advantage in nature for biologists to be able to explain the extent of polymorphism within populations, but of course since much of the lab research is done on flies and worms it might not be totally relevant to humans. Only higher vertebrates have adaptive immune systems, so the MHC genes and their immune phenotype might not fall within expectation.

Addendum: I assume readers will play by the maxim: my aesthetic preferences aren't everyone's aesthetic preferences, and arguments from personal incredulity or deep introspection are frowned upon. I also suggest you read the paper if you are going to comment on it.

1 - This is why William Hamilton appealed to long term frequency dependent effects, while some theorists are looking to synergistic epistasis as the theoretical underpinning for the ubiquity of sex in complex organisms.

2 - The beauty of multiracial individuals is probably somewhat in vogue in the cultural zeitgeist right now, but let us recall that a century ago mixed individuals were assumed to be maladapted and unfit mongrels, so perceptions can change based on cultural preconceptions.

3 - That research is not totally orthogonal, if females prefer similar MHC profiles than their children are more likely to be homozygous at a locus than if they prefer dissimilar MHC profiles.

Posted by razib at 08:49 PM