La signification évolutive de la calvitie

The evolutionary significance and social perception of male pattern baldness and facial hair

(Frank Muscarella, Michael R. Cunningham)

Abstract

Both male facial hair and male pattern baldness are genetically based, suggesting that they contributed to fitness. The multiple fitness model provides an evolutionary interpretation of the social perception of male pattern baldness and beardedness in terms of the multidimensional meaning of physical maturational stages. Male facial beardedness is associated with the sexual maturation stage and is hypothesized to signal aggressive dominance. Male pattern baldness, by contrast, is associated with the next stage of physical maturation, termed senescence. Pattern baldness may signal social maturity, a non-threatening form of dominance associated with wisdom and nurturance. We tested these hypotheses on social perceptions using manipulated male facial stimuli. We presented faces with three levels of cranial hair, including full, receding, and bald, and two levels of facial hair, beard with moustache and clean shaven. Consistent with the model, a decrease in the amount of cranial hair was associated with increased perceptions of social maturity, appeasement, and age, and decreased perceptions of attractiveness and aggressiveness. Targets with facial hair were perceived as more aggressive, less appeasing, less attractive, older, and lower on social maturity than clean shaven faces.

Is there an evolutionary benefit to being bald? 

(New Scientist)

Mike Follows, Sutton Coldfield, West Midlands, UK:

A 1996 study suggested male pattern baldness signals maturity and gravitas. This may be a legacy from our past. Grooming that takes place among great apes can involve plucking hair – higher status apes receive more grooming and can exhibit alopecia.

What’s more, in 2008, a study suggested that because it increases the area of skin exposed to sunlight, male pattern baldness may have evolved to increase the production of vitamin D. This vitamin protects against prostate cancer, which interferes with reproduction and can lead to premature death.

But the onset of male pattern baldness tends to be after men reach fatherhood, so too late to remove bald men from the potential gene pool. This suggests it doesn’t bestow any evolutionary advantage or disadvantage.

However, they may be seen as superior mates and better marriage material because they are perceived as more nurturing towards offspring and less likely to attract rival females.

Greying hair may have a similar association. For example, dominance in a gorilla troop is signalled with a silver patch of hair on the backs of older males.