Human sexual selection: male voice and face shape Part 1

Continuing from my last post, I want to look at the other factor thought to influence male features (face and voice): female-male interactions, where females select males, favouring traits that females find attractive. A man’s face and voice works as advertising for their mate value and health. This was shown by a study that asked women to rate attractiveness of digital altered males faces and voices, women would often rank more robust faces and deeper voices more attractive. These results shows that females will have an effect on male feature. It was concluded from this that an “average” male face and voice was the most attractive. However, the case in not so simple, there are trade-offs with mating with over masculine men.

Images showing a digital alter male face to look more or less masculine.

Having more masculine features is generally linked with higher levels of testosterone, however heighten testosterone may have other consequences for a man’s health and behaviour. Higher levels of testosterone can act as an immunosuppressant, affecting a man’s general health and so his long-term mate value. Though, there has been studies showing that the level of suppression maybe condition dependent and therefore have greater impact on males in poor-condition. This would mean a masculine male would be strong and dominate when in good- condition, but once his health declines he would become a poor mate choice. And so, this would allow less dominate males to have equal mate success, because they would be around for a longer time, and would be a better as a long-term mate selection for a females.

Another disadvantage of selecting masculine mates is the difference in behaviour. Evidence has shown a positive correlation between testosterone levels and male infidelity, violence, divorce rate and commitment to offspring. More masculine males are perceived to possess other undesirable traits such as emotionally cold and uncommunicative. These undesirable behaviours result in women favouring men with less dominate traits as long-term partners. It is therefore not as easy as being the most masculine to win mates, it is also depends on one the long term befits associated as a partner. In addition to this, female preferences maybe also be dependent other factors, such as her own attractiveness; hormonal levels during different stages of menstrual cycle; as well as past experiences with men.

As one may imagine, it is not all so simple.  Human attractiveness is based on far more than the initial appearance, of which there is multitude of variables. The research conducted often asks basic question- attractiveness 1-10-  using portrait images, this approach, which is good for standardisation, fails to take into account gait, fashion, personal, pheromones etc., though it does provide and interesting perspective from which to look.

References

Puts, D.A., Jones, B.C. & DeBruine, L.M. 2012, "Human sexual selection ", Journal of sex research, vol. 49, no. 2-3, pp. 227.

Human sexual selection: male voice and face shape Part 1

Human sexual selection is a complex system of interactions, even with our modern social constructs and laws in the mix nature still plays its role. Humans are highly sexual dimorphic primate with differing body form and behaviours for males and females. Here I wanted to look at what selection pressures determine male features, in particular the traits of male voice and face shape. I did not look at female features here, as some research suggests that female face shape and voices are only somewhat influents by sexual selection, and that selection acts mainly on males.

Male features are thought to be influence by two selection factors: male-male interaction, where males are in contest with each other, favouring traits for excluding other males; and female-male interactions, where females select males, favouring traits that females find attractive. In male-male interaction, a male fends off other males in two ways by actual threat or by potential threat – display of dominance.  Although, actual threats may be less important in our modern society with law preventing them, they would have been in an evolutionary context a key factor. A perceived threat, on the other hand, may still affect mate success, as it would exclude other males. Being able to exclude other males would give a greater chance of mate success. And so, being/showing dominance by your outward appearance, from a male-male perspective, can be advantageous.

Studies have shown that there is a relationship between masculine vocal and facial features, and dominance. If then dominance led to better success, natural selection would act on these two traits. There was found to be a correlation between males having a lower more masculine voice and the perception of dominance by other males. In a study, it was shown that men would alter the pitch of their voice in accordance with their perceived dominance. It was seen that, a man would lower his pitch when talking to a male he thinks to be weaker than himself, and raise the pitch if he thinks he is weaker.

 By a similar token, men with stronger jaw line are perceived as being more masculine and more dominant. A stronger jaw line is thought be dominant in both appearance and practicality. Unlike voice, having a strong jaw would help in an actual fight; strong jaws are less likely to be broken. It is also thought that, facial hair may have evolved to increase the apparent size of the jaw. This could explain why some studies had found that: a male’s face with a beard was rated more dominate than clean-shaven one. Therefore, it can be seen that male-male interactions are controlled by the traits that intimidate/exclude competitors by a show of dominance.

to be continued 

References

Puts, D.A., Jones, B.C. & DeBruine, L.M. 2012, "Sexual selection on human faces and voices", Journal of sex research, vol. 49, no. 2-3, pp. 227.
C.L Apicella, D.R Feinberg & F.W Marlowe 2007, "Voice pitch predicts reproductive success in male hunter-gatherers", Biology Letters, vol. 3, no. 6, pp. 682-684.
Boothroyd, L.G., Cross, C.P., Gray, A.W., Coombes, C. & Gregson-Curtis, K. 2011, "Perceiving the facial correlates of sociosexuality: Further evidence", Personality and Individual Differences, vol. 50, no. 3, pp. 422-425.