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

Sylvia Kirchengast,Kerrin Christiansen

doi:10.3390/sym9050072

Sylvia Kirchengast, Kerrin Christiansen

Open Access

https://doi.org/10.3390/sym9050072

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Journal: Symmetry	Publication Date: May 15, 2017
Citations: 9	License type: CC BY 4.0

Affiliation: University of Vienna, Universität Hamburg

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.

Highlights

Symmetry, which is widely found in nature, is often seen as an ideal and is defined as correspondence in size, shape and relative position of parts on opposite sides of a median plane or a dividing line [1]
The present study focuses on association patterns between fluctuating as well as directional asymmetry patterns and adult androgen levels among two traditional societies of southern Africa
Another shortcoming is the low number of anthropometric features indicating asymmetry patterns

Summary

Introduction

Symmetry, which is widely found in nature, is often seen as an ideal and is defined as correspondence in size, shape and relative position of parts on opposite sides of a median plane or a dividing line [1]. The body plan of Homo sapiens—as typical of vertebrates—is generally described as bilaterally symmetrical, this bilateral symmetry, is broken by consistently asymmetric placement of some internal organs such as heart, spleen, liver or gut, and the asymmetric development of some paired organs such as lungs or the brain hemispheres [2]. Homo sapiens can be described as pseudo-bilateral. Symmetry is interpreted as an ideal among Homo sapiens. This is mainly because even small deviations from perfect bilateral symmetry reflect disruptions of development homeostasis. Asymmetry of bilateral structures is Symmetry 2017, 9, 72; doi:10.3390/sym9050072 www.mdpi.com/journal/symmetry

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