Abstract
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.
Highlights
Since the work published by Gall in 1835 [1], there has been a persistent interest in exploring methods aimed to predict the behavioural, moral, ethic, or emotional status of an individual departing from their physical appearance in general, and from their craniofacial shape in particular
The overall low Fst values obtained for fWHR (0.014–0.166) in comparison with other indices (Table 1) indicate that the pattern of within versus between-group variation is similar to estimates based on neutral DNA, protein, enzyme, and blood-group polymorphisms [29], rather than what is expected to a marker subjected to strong sexual selection
Results concerning fWHR dimorphism comparisons on groups with ethnographically documented variable levels of within-group interpersonal violence, and fWHR comparison in individuals subjected to prosecution decisions based on different levels of violence with non-prosecuted individuals of the same population are presented in Figure 2a and b respectively
Summary
Since the work published by Gall in 1835 [1], there has been a persistent interest in exploring methods aimed to predict the behavioural, moral, ethic, or emotional status of an individual departing from their physical appearance in general, and from their craniofacial shape in particular. Since the form of the head is a good predictor of brain shape, it follows from this perspective that an individual’s morality could be predicted by its head shape. Along with research on the socio-cultural variability of human behaviours performed from the last half of the 20th century, it has been demonstrated that there is no straightforward connection between behaviour and physical appearance [3]. Even though changes on behaviour likely facilitated the evolutionary success of early hominines, behaviour is a very complex and plastic phenotype that can be quickly reshaped through education and other socio-cultural practices [4,5,6,7,8]. It has been shown that neuronal and brain functions are amenable to plasticity [9]
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