Date of Award




Document Type


Degree Name

Doctor of Philosophy (PhD)


Department of Psychology


Behavioral Neuroscience

Content Description

1 online resource (iv, 66 pages) : illustrations.

Dissertation/Thesis Chair

Gordon G. Gallup

Committee Members

Christine K. Wagner, Daniel D. White


digit ratio, fluctuating asymmetry, hand grip strength, leg to torso length ratio, psychological masculinity/femininity, Sex-typical body shape, Sex differences, Sex differences (Psychology), Biological fitness

Subject Categories

Biological Psychology | Psychology


According to evolutionary theory, sex-typical body shapes (a man's muscular physique and a woman's hourglass figure) are an outcome of evolutionary adaptation in reproductive fitness because they convey information about gene quality, health and fertility, which are important elements for mate selection. The purpose of this study was to investigate whether sex-typical body shape predicts individual variation in morphological traits that signal quality [fluctuating asymmetry (FA), hand grip strength (HGS), digit ratios (2D:4D) and leg-to-torso ratio (LTR)] and in psychological masculinity/femininity and the role of these in reproductive fitness. The results revealed that a man's masculine body shape predicted low FA and high HGS. In particular, HGS was a primary predictor of male body masculinity. Moreover, men with more wedge-shaped bodies showed earlier sexual maturation and had more sexual opportunities, whereas such effects were not observed in women. These findings indicate that a man's masculine body shape is an honest signal of quality and is linked to reproductive success. With regard to psychological masculinity/femininity, sex-typical body shape was shown to be independent of psychological gender traits. However, individuals who possessed both a high degree of body attractiveness (males with more wedge-shaped bodies and females with more accentuated hourglass figures) and high levels of psychological masculinity had the greatest number of sex partners. This association implies that the combination of high degree of body attractiveness and high levels of psychological masculinity signals optimal conditions for reproductive success in both sexes.