Abstract
It has been suggested that the deep voices of men have been selected through intrasexual competition to signal dominance, threat and masculinity to competitors, whereas the high voices of women have been selected through intersexual competition to signal fertility and femininity. Indeed, beyond the linguistic message, the human voice conveys valuable biological and social information about the quality and condition of the speakers such as sex, age, body configuration, personality and possibly social status. These cues are crucial when assessing competitors and potential sexual partners. In this thesis, we studied the functional role of the human voice through the lens of sexual selection. Firstly, our work suggests that vocal preferences are not universal and depend on the culture under study, since several of our results in a population of French speakers show that men are attracted by relatively low-pitched voices in women, as opposed to what has been observed in English speaking populations. Likewise, most studies have focused on pitch and timbre, but our results suggest that phenotypic quality may be expressed through other elements of voice quality such as roughness, breathiness, and various prosodic elements. Secondly, the evolutionary interpretations hitherto evoked in the literature to explain these preferences remain unsatisfactory. Indeed, our results show that, on one hand, men's voices are not correlated with testosterone levels, suggesting that they are not a “honest” signal of immunocompetence and, on the other hand, that vocal modulation, which corresponds to a dynamic modification of voice quality in an interactional context, emphasizes the importance of studying voice in ecologically valid situations. Finally, we have shown through the principle of sound symbolism that the sexual dimorphism of the human voice is also reflected in the sound composition of first names and their attribution according to sex. To conclude, the present work offers several new lines of research and establishes sexual selection as a key evolutionary paradigm to study the human voice.