Facial shape uncorrelated with aggression

Facial shape uncorrelated with aggression

Of interest is the calculation of sexual dimorphism for a variety of indices in different datasets (Figure 1; left). The figure caption:

Box and whisker plots of global sexual dimorphism computed across the different databases. Indices that differed significantly among sexes (after t-test for independent samples) are shown in solid grey. A) Howells database; b) Pucciarelli database, c) 2D Geometric Morphometric database, d) 3D Geometric Morphometric database, e) Patagonian groups database. Square: median; box: 25%–75%; whisker: minimum-maximum values.

Also of interest Figure S1 (bottom right), which breaks down the sexual dimorphism in different populations. The caption reads:

Box and whisker plots of fWHR depicting inter-sexual differences across the populations of each database. a) Howells database; b) Pucciarelli database, c) 2D Geometric Morphometric database, d) 3D Geometric Morphometric database, e) Patagonian groups database. Square: median; box: 25%–75%; whisker: minimum-maximum values. Orange: females, blue: males. Populations showing significantly greater male fWHR (after t-test for independent samples) are marked with grey boxes.

It would be nice if more anthropometric datasets were publicly available. Perhaps some of the above-mentioned are, but I didn't see any mention of how to obtain them in the paper itself.


PLoS ONE 8(1): e52317. doi:10.1371/journal.pone.0052317

Lack of Support for the Association between Facial Shape and Aggression: A Reappraisal Based on a Worldwide Population Genetics Perspective

Jorge Gómez-Valdés et al.

Antisocial and criminal behaviors are multifactorial traits whose interpretation relies on multiple disciplines. Since these interpretations may have social, moral and legal implications, a constant review of the evidence is necessary before any scientific claim is considered as truth. A recent study proposed that men with wider faces relative to facial height (fWHR) are more likely to develop unethical behaviour mediated by a psychological sense of power. This research was based on reports suggesting that sexual dimorphism and selection would be responsible for a correlation between fWHR and aggression. Here we show that 4,960 individuals from 94 modern human populations belonging to a vast array of genetic and cultural contexts do not display significant amounts of fWHR sexual dimorphism. Further analyses using populations with associated ethnographical records as well as samples of male prisoners of the Mexico City Federal Penitentiary condemned by crimes of variable level of inter-personal aggression (homicide, robbery, and minor faults) did not show significant evidence, suggesting that populations/individuals with higher levels of bellicosity, aggressive behaviour, or power-mediated behaviour display greater fWHR. Finally, a regression analysis of fWHR on individual's fitness showed no significant correlation between this facial trait and reproductive success. Overall, our results suggest that facial attributes are poor predictors of aggressive behaviour, or at least, that sexual selection was weak enough to leave a signal on patterns of between- and within-sex and population facial variation.

Link

Blue eyes, facial shape, and perceived trustworthiness

Blue eyes, facial shape, and perceived trustworthiness

A new paper suggests that Czechs tend to view brown-eyed people as more trustworthy than blue-eyed ones, although the difference seems to be due to differences in facial structure between brown- and blue-eyed people; an article in Scientific American covers this new paper fairly well.

I will add that the location of the sample (Czech Republic) is interesting, as it is intermediate between the Baltic area (where light eye pigmentation reaches quasi-fixation, and, hence, presumably, light eyes are not viewed with any suspicion) and southeastern Europe and Anatolia (where there is well-documented folklore about the association of eye pigmentation with the "evil eye").

I had encountered an explanation for this phenomenon in a work by P.G. Maxwell-Stuart on ancient color terminology, in which an argument was made that in predominantly dark-eyed peoples, light eyes -because of their rarity- may have an indirect association with glaucoma and viewed suspiciously for that reason -perceived chance of morbidity; the Wikipedia article suggests the phenomenon is explained on the basis of encounters with light-eyed foreigners who might be unaware of cultural norms against direct staring. But, the frequency of different eye colors in Czechs today is probably fairly balanced, making either explanation unsatisfactory.

Getting back to the article at hand, it appears that -at least in men- blue eyes are associated with a suite of other facial features. Razib offers the suggestion that the possible disadvantage conferred by reduced "trustworthiness" may be compensated in another way through pleiotropy, and the authors suggest:

The trade-off between a preference for colorful and visible physical features and the advantage of a trustworthy-looking face might have contributed to the high variability of European eye and hair color.

But, I'll get back to the possibility that the phenomenon may be driven by a historical process, i.e., the encounter between peoples who differed statistically in eye pigmentation and other facial features.

The picture on the left is from the Gospel Book of Otto III and is about 1,000 years old. Now, all eyes appear conventionally painted as brown dots here, but we can notice that the different provinces are painted with different hair color, with Sclavinia being darker than Germania and lighter than Gallia and Roma. This might make some sense, since Germanic peoples are thought to have originated in northern Germany/southern Scandinavia, and Slavs in C/E Europe (perhaps somewhere between Poland and Ukraine).

This raises the possibility that early Slavs were phenotypically somewhere in the middle of the European pigmentation continuum, although their exact position therein might only be determined with ancient DNA evidence. Today, the lighter-pigmented Slavs are probably those close to the Baltic (e.g., Russians and Poles), the darker ones from the Balkans, perhaps indicating different types of gene flow ("northern" Germanic/Baltic/Finno-Ugrian vs. "southern" Thraco-Illyrian-Greek).

If this is correct, then the slightly negative association of blue eyes in the present Czechs might be a culturally-transmitted vestige of inter-ethnic contact during the medieval period. A possible test would be to repeat the experiment with the Czechs' German neighbors, in which the process ought to operate in reverse -if my hypothesis is correct.

PLoS ONE 8(1): e53285. doi:10.1371/journal.pone.0053285

Trustworthy-Looking Face Meets Brown Eyes

Karel Kleisner et al.

We tested whether eye color influences perception of trustworthiness. Facial photographs of 40 female and 40 male students were rated for perceived trustworthiness. Eye color had a significant effect, the brown-eyed faces being perceived as more trustworthy than the blue-eyed ones. Geometric morphometrics, however, revealed significant correlations between eye color and face shape. Thus, face shape likewise had a significant effect on perceived trustworthiness but only for male faces, the effect for female faces not being significant. To determine whether perception of trustworthiness was being influenced primarily by eye color or by face shape, we recolored the eyes on the same male facial photos and repeated the test procedure. Eye color now had no effect on perceived trustworthiness. We concluded that although the brown-eyed faces were perceived as more trustworthy than the blue-eyed ones, it was not brown eye color per se that caused the stronger perception of trustworthiness but rather the facial features associated with brown eyes.

Link

The German Hyperbrachycephals

The German Hyperbrachycephals

According to the Nordicist school, European achievement is primarily due to the tall, blond, dolichocephalic race. The only problem with this theory, which achieved such popularity in the 19th and early 20th centuries, is that when the skulls of prominent Europeans and Germans were measured there was no evidence of an overrepresentation of dolichocephals among them: indeed, most of them were brachycephalic, many of them tending to the extreme hyperbrachycephalic form, as the following passage illustrates.

Friedrich Hertz, Rasse und Kultur: eine kritische Untersuchung der Rassentheorien, 3. ed., Alfred Kröner, Leipzig, 1925, p.163

Sehen aber die Genies wirklich in der Regel so aus [DP: Germanisch Typus]? Genaue Feststellungen liegen leider nur selten vor. Immerhin können wir sagen, dass die Genies sehr häufig - vielleicht selbst in der Mehrzahl der Fälle - diesen Anforderungen nicht entsprechen. Vor allem ihr Schädel nähert sich meist ganz bedenklich der "Kreislinie tierischen Wohlbehagens", wie Chamberlain so schön sagt. Bismarck, Luther, Laplace, Napoleon, Pascal, Raphael, Beethoven, Haydn, Schubert sind einige Beispiele von Rundköpfen, ja, es scheint gerade die extreme Form der Rundköpfigkeit, die Hyperbrachycephalität, die man mit dem Index 85 beginnen lasst, unter ihnen sehr häufig zu sein). Schillers Schadel mit seinem Index von 84 steht knapp an inhrer Grenze, Kant mit seiner Indexnummer von 88.5 war ein ganz ausgesprochener Hyperbrachycephale. Hamerling hatte den Index 85.3, Schopenhauer den von 86, Leibniz gar einen von 90.3.

UPDATE (2 March 2008)

Franz Weidenreich, "The Brachycephalization of Recent Mankind", Southwestern Journal of Anthropology, Vol. 1, No. 1. (Spring, 1945), p. 9.

One can imagine the shock an intelligent German reader suffered when he remembered that many of the great German heroes from Bismarck down to Hindenburg and Hitler were brachycephalics and even hyperbrachycephalics, and that the three greatest philosophers Germany has produced-Leibniz, Kant, and Schopenhauer-had round heads in the most extreme form (Fig. 2, No. 4, Leibniz, skull index 90.3[!]; NO. 5, Kant, skull index 88.5; No. 6, Schopenhauer, head index 90.0 [!).