It is interesting the fact that both the level of testosterone and a person’s higher predisposition towards an aggressive behavior can be displayed by his or her facial traits. More exactly, some scientists claim that such a facial indicator as the facial width-to-height ratio (fWHR) depends on the level of testosterone in one’s organism: a higher ration in favor of the width suggests a higher level of testosterone and, respectively, a higher degree of assertiveness and aggressiveness. This facial indicator can be a predictor of the more aggressive behavior of the respective persons [Carré, McCormick, 2008; Carré et al., 2009].
Other studies show, complementarily, that men who have a wider face can have better sportive performances [Tsujimura, Banissy, 2013]; moreover, they have the tendency to behave non-ethically, to display psychopathic traits and they are less prone to be afraid in risky situations [Geniole et al., 2014; Carré, 2014]. These men have more children than the rest, therefore enjoying a higher level of prolificacy, which can also be an effect of the high level of testosterone in their bodies [Loehr, Hara, 2013].
There also exists a hypothesis which says that a larger cheekbone and a harder zygomatic bone may be a trait that defines the more aggressive men and that renders them more resistant to direct hits; and since they get involved in violent actions more often, they need thicker bones that would protect them from traumas [Lefevre et al., 2014].
The fWHR ratio has been identified in other non-human species like, for example, in Capuchin monkeys (Sapajus spp.). For them, the facial ratio in width’s favor is associated with the rank of alpha-male. In the case of this species, the phenomenon is also valid for females: those who have a wider face display a more assertive temper, more dominance and aggressiveness. It has been noted that this ratio can be observed only in adult individuals, meaning that facial changes take place during puberty, along with sexual maturation and abundant secretion of testosterone [Lefevre et al., 20142].
There exists another unexpected indicator of the level of testosterone and aggressive male behavior – the ration between the index and the ring fingers; this strange phenomenon is called “digit ration” (or 2D:4D ratio). Since 19th century, scientists have noticed that, in men, the ring finger is frequently longer than the index finger, while this difference is almost imperceptible in women. It can be explained in the following manner: during early embryo stage, the development of hand fingers is influenced by the hormonal balance in the mother’s uterus; the higher level of androgen hormones correlates with the greater length of the ring finger, as compared to the index finger.
Men who have a longer ring finger will display, at maturity, a higher degree of aggression, more masculinized facial traits, better sportive abilities, higher physical strength, propensity towards domination and leadership. It look like, along with intrauterine hormonal influence, there is also a sexual selection that favors men with longer ring finger and that ensures the birth of a high number of boys with these traits from one generation to another , , [Manning, 2002; Bailey, Hurd, 2005; Meij van der et al., 2012; Longman et al., 2015].
It is very curious the fact that women with homosexual inclinations have a masculinized 2D:4D ratio, meaning that, during the embryo stage, they have made contact with a higher level of androgenic hormones [Grimbos et al., 2010].
There is a hypothesis which states that feminism (in its radical version) can be explained, at least partially, through the impact of androgenic hormones on the fetus. Only a small number of women become truly feminists – a phenomenon known as ”the feminists paradox” – and scientists tried to find out if there are any biological grounds for such a paradox. It has beed found that, indeed, in feminists, the 2D:4D ratio is similar with the masculine one – a correlation that explains why they also exhibit a set of physiological and psychological characteristics that are associated with masculinity [Madison et al., 2014].
Thus, testosterone has very profound influences in shaping the human behavior, and these influences already take place at the stage of intrauterine ontogenesis. Machismo and feminism have some very interesting relations with digit ratio and facial traits.
If we are to extend the list of physical indicators that signal a higher level of testosterone and aggression, it is worth mentioning the curious hypothesis that was proposes by the American Professor of Psychology J. Phipippe Rushton, who is specialized in studying the relationship between genetic and behavior; he published in 2012 a paper, in which he claims that the color of the skin, more exactly the biological factors that ensure pigmentation – melanocortins, can have a special role in the process of determining the aggressive behavior in animals and humans.
Indeed, certain prior studies, carried on tens of species of vertebrates, have shown that dark pigmentation of an individual’s skin directly correlates with a higher degree of aggressiveness and sexual activity of this individual within population. This happens because the melanocortin receptors activate, among other things, the production of testosterone and other hormones that have an impact on behavior [Ducrest et al., 2008; Mafli et al., 2011; Roulin, Ducrest, 2011].
Rushton has launched the hypothesis that people also, due to their phylogenetic relationship with the other groups of animals, have inherited a mechanism of correlation between pigmentation and aggression. Individuals that have a darker color of the skin are more aggressive, no matter if we are talking about individuals from the same ethno-racial group or the difference between ethno-racial groups. In order to confirm his hypothesis, Rushton comes with numerous statistical data on the incidence of different social phenomena that are positively correlated with the degree of pigmentation of the individuals of a nation [Rushton, Templer, 2012].
Rushton’s theses concerning racial differences can be accused of having an rasist subtext, but the ideas presented by this scientist are useful for the obiectivity of a clear and upright vision on human nature and they once again highlight the subtleties that complex biological mechanisms have in the formation of social behavior.
© Dorian Furtună, ethologist
Photo: Bruce Lee / http://i051.radikal.ru/1003/31/9ac43a1e4667.jpg
1. Digit ratio // http://en.wikipedia.org/wiki/Digit_ratio
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