Facial width-to-height ratio
(fWHR) has been proposed as a sexually dimorphic signal in humans that develops
under the influence of pubertal testosterone (T); however, no studies have
examined the association between fWHR and T during the phase in which facial
growth is canalized-adolescence.
In a sample of adolescent Tsimane males, we
evaluate the relationship between T, known T-derived traits (i.e. strength and
voice pitch), and craniofacial measurements. If fWHR variation derives from T's
effect on craniofacial growth during adolescence, several predictions should be
supported: 1) fWHR should increase with age as T increases, 2) fWHR should
reflect adolescent T (rather than adult T per se), 3) fWHR should exhibit
velocity changes during adolescence in parallel with the pubertal spurt in T,
4) fWHR should correlate with T after controlling for age and other potential
confounds, and 5) fWHR should show strong associations with other T-derived
traits. Only prediction 4 was observed.
Additionally, we examined three
alternative facial masculinity ratios: facial width/lower face height,
cheekbone prominence, and facial width/full face height. In contrast to fWHR,
all three alternative measures show a strong age-related trend and are
associated with both T and T-dependent traits.
Overall, our results question
the status of fWHR as a sexually-selected signal of pubertal T and T-linked
traits.
Below: Facial landmarks used to derive facial masculinity ratios
Below: Facial masculinity ratios (a/b) by age, testosterone, and strength
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By:
- 1Department of Anthropology, Boston University, Boston, Massachusetts, United States of America.
- 2Department of Anthropology, University of California Santa Barbara, Santa Barbara, California, United States of America.
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