Androgen levels and body size are associated with directional as well as fluctuating asymmetry patterns in adult !Kung San and Kavango males from northern Namibia

Abstract

Fluctuating asymmetry is mainly interpreted as an indicator of developmental instability, while directional asymmetry of the upper limbs is associated with handedness. The association patterns between adult androgen levels and fluctuating as well directional asymmetry patterns are still unclear. In the present study, the association between adult androgen levels, body size and directional as well as fluctuating asymmetry pattern was tested among !Kung San and Kavango males from northern Namibia. Serum concentrations of testosterone (Tser) and 5α-dihydrotestosterone (DHT) as well as salivary testosterone (Tsal) concentrations were obtained from 114 !Kung San and 136 Kavango men aged 18-40 years. Fluctuating and directional asymmetry were determined from eight paired traits. Signed and unsigned asymmetry, composite fluctuating and directional asymmetry were calculated. !Kung San males surpassed their Kavango counterparts in the directional asymmetry but also in composite directional asymmetry (CDA) significantly. Among !Kung San males, DHT correlated significantly negatively with parameters of fluctuating asymmetry as well as with parameters of directional asymmetry. Free testosterone of the saliva correlated significantly negatively with asymmetry of hand length. Among Kavango males, DHT is negatively associated with foot breadth asymmetry, but positively associated with wrist asymmetry. Although the correlations between asymmetry patterns and androgen levels are weak, it can be concluded that among !Kung San males adult androgen levels are negatively associated with a high quality phenotype.