Abstract
BackgroundIn this paper, we investigate facial sexual dimorphism and its’ association with body dimorphism in Maasai, the traditional seminomadic population of Tanzania. We discuss findings on other human populations and possible factors affecting the developmental processes in Maasai.MethodsFull-face anthropological photographs were obtained from 305 Maasai (185 men, 120 women) aged 17–90 years. Facial shape was assessed combining geometric morphometrics and classical facial indices. Body parameters were measured directly using precise anthropological instruments.ResultsSexual dimorphism in Maasai faces was low, sex explained 1.8% of the total shape variance. However, male faces were relatively narrower and vertically prolonged, with slightly wider noses, narrower-set and lower eyebrows, wider mouths, and higher forehead hairline. The most sexually dimorphic regions of the face were the lower jaw and the nose. Facial width-to-height ratio (fWHR), measured in six known variants, revealed no significant sexual dimorphism. The allometric effects on facial traits were mostly related to the face growth, rather than the growth of the whole body (body height). Significant body dimorphism was demonstrated, men being significantly higher, with larger wrist diameter and hand grip strength, and women having higher BMI, hips circumferences, upper arm circumferences, triceps skinfolds. Facial and body sexual dimorphisms were not associated.ConclusionsFacial sex differences in Maasai are very low, while on the contrary, the body sexual dimorphism is high. There were practically no associations between facial and body measures. These findings are interpreted in the light of trade-offs between environmental, cultural, and sexual selection pressures.
Highlights
In this paper, we investigate facial sexual dimorphism and its’ association with body dimorphism in Maasai, the traditional seminomadic population of Tanzania
Sexual dimorphism of Maasai facial shape The degree of sex differences in facial shapes of Maasai were first tested on the general sample including subjects of all ages
Results of the analysis revealed that increase in sexual dimorphism in facial shape within the mid-adult cohort was at least partially caused by the body mass index (BMI) differences between men and women, since after controlling for BMI, sexual dimorphism in Maasai facial shape within the mid-adult cohort decreased (Fig. 3c)
Summary
We investigate facial sexual dimorphism and its’ association with body dimorphism in Maasai, the traditional seminomadic population of Tanzania. We discuss findings on other human populations and possible factors affecting the developmental processes in Maasai. [27, 28] in the emergency of population variations in facial and body sexual dimorphism in humans has been an object of intensive discussions [3, 8, 29]. Cranial (facial) form and robusticity demonstrate substantial variation related to climate and ecology (geography) [30], and sexual dimorphism varies between races and ethnics [31,32,33,34,35,36,37,38]
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