Testosterone is Not a Handicap
Many contemporary beauty researchers assume/conclude that attractive, sexually dimorphic features in men (strong jaws, increased lean muscle mass, etc.) are true signals of mate quality. This model is best illustrated in peacock tail feathers: the size and color of the train makes the male more sexually attractive to peahens. Rather than being just an attractive, but functionally useless ornament, this weighty handicap is an honest signal to peahens of the male’s quality – because this tail is so costly to possess. Any peacock that can thrive with this large disadvantage must be well-adapted – that is, possess good genes.
Testosterone inhibits immune functioning. Given this, the basic argument is that any potential mate with testosterone-related features must have “good genes” in order to thrive with the testosterone handicap. One big problem with the testosterone as a handicap hypothesis is that testosterone is not merely an immunity suppressant. Testosterone produces benefits as well:
The primary fitness benefits of testosterone are multifaceted, including support for optimal spermatogenesis, the development and maintenance of secondary sexual characteristics that augment male competitiveness and attractiveness, as well as libido. Other associations include competitive ability and possible relationships with social dominance. (Bribiescas & Ellison, p. 104)
Thus, testosterone’s effects involve trade-offs: there are pros and cons to having testosterone coursing through one’s veins.
The second big problem with this hypothesis is that there is no evidence for this phenomenon in mammals. Roberts, et.al. (2004) found evidence for the immunocompetence handicap hypothesis (what I am calling the testosterone as handicap hypothesis) in birds and reptiles, but not mammals. Nunn, et.al. (2008) subsequently corroborated this conclusion with regard to mammals.
Arguments which assume sexually attractive, dimorphic features in human males are costly handicaps – and thus true signals – are overlooking the complex influence of testosterone in human adaptations as well as overlooking the lack of evidence for applying this concept to mammals generally and humans specifically.
Image courtesy of Rhodney Carter, Wikipedia Commons.
Nunn, C., Lindenfors, P., Pursall, E., & Rolff, J. (2009). On sexual dimorphism in immune function Philosophical Transactions of the Royal Society B: Biological Sciences, 364 (1513), 61-69 DOI: 10.1098/rstb.2008.0148
ROBERTS, M., BUCHANAN, K.L., & EVANS, M.R. (2004). Testing the immunocompetence handicap hypothesis: a review of the evidence Animal Behaviour, 68 (2), 227-239 DOI: 10.1016/j.anbehav.2004.05.001