Intra- and Intersexual Selection on Men: Their Relative Importance and Hormonal Underpinnings

von Tobias Kordsmeyer
Dissertation
Datum der mündl. Prüfung:2018-01-17
Erschienen:2018-01-26
Betreuer:Prof. Dr. Lars Penke
Gutachter:Prof. Dr. Lars Penke
Gutachter:Prof. Dr. Mitja Back
Gutachter:Prof. Dr. Julia Ostner
Gutachter:Prof. Dr. Margarete Boos
Gutachter:Dr. Bernhard Fink
Gutachter:Prof. Dr. Annekathrin Schacht
Zum Verlinken/Zitieren: http://dx.doi.org/10.53846/goediss-6704

 

 

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Male competition is an important influence on the distribution of resources, such as mates, food or territory, and has been shown to be more strongly implicated, compared to female mate choice, in sexual selection on men. In two studies, the role of different facets of men’s personality, sexually dimorphic traits and hormones in competitive behaviour and sexual selection was investigated. Firstly, increases in the hormone testosterone (T) have been found after intrasexual competitions and exposure to females. Such T reactivity may also affect relevant personality state changes that are observable to others, whereby exact associations, also under potential buffering effects of Cortisol (C), are unclear. In a preregistered study, we aimed at inducing T increases in young men (N=165) through dyadic intrasexual competitions while exposed to a female experimenter. We investigated self-reported and video-based observer-rated personality state changes, as captured by the Interpersonal Circumplex and social impressions, in relation to hormonal levels. Results revealed increases in competitiveness, dominance and self-assurance, relative to a control group and moderated by T reactivity and partly by TxC interactions. This provides further insights into how hormonal and personality responses to challenges are intertwined in men, and partly supports a role of T in mediating a life history trade-off between mating/competing and parenting, as well as signalling dominance to rivals and potential mates. Secondly, in the same sample of men, we sought to provide further evidence on the effects of men’s physical dominance and sexual attractiveness on mating success and hence in sexual selection. Objective measures and subjective ratings of male sexually dimorphic traits (height, vocal and facial masculinity, upper body size from 3D scans, physical strength, and baseline testosterone) and observer perceptions of physical dominance and sexual attractiveness were assessed and associated with mating success in a partly longitudinal design. Results revealed that physical dominance, but not sexual attractiveness, predicted mating success. Physical dominance mediated associations of upper body size, physical strength, as well as vocal and facial physical dominance and attractiveness with mating success. These findings thus suggest a greater importance of intrasexual competition than female choice in human male sexual selection.
Keywords: sexual selection; life history; male competition; hormones; personality states
 
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