Emancipation of the voice: Vocal complexity as a fitness indicator.
Although language is generally spoken, most evolutionary proposals say little about any changes that may have induced vocal control. Here I suggest that the interaction of two changes in our species-one in sociality, the other in life history-liberated the voice from its affective moorings, enabling it to serve as a fitness cue or signal. The modification of life history increased the helplessness of infants, thus their competition for care, pressuring them to emit, and parents (and others) to evaluate, new vocal cues in bids for attention. This change elaborated and formalized the care communication system that was used in infancy and, because of parental adoption of social criteria, extended it into childhood, supporting the extrafamilial relationships that intensify in those stages. The remodeling of life history, in conjunction with intensified sociality, also enhanced vocal signaling in adolescence-a second stage that is unique to humans-and adulthood. Building on the new vocal skills and fitness criteria that emerged earlier, I claim that males with ornamented speech enjoyed advantages in their pursuit of dominance and reproductive opportunities in evolutionary history, as they do today. There are implications of this scenario for the mechanistic level of vocal diversification. Today, intentionality plays a role both in the instrumental crying of infants and the modulated vocalizations of adults. In evolutionary history, I claim that in both cases, spontaneously emitted behavioral cues elicited perceptible responses, giving rise to strategic signals that were sent, and processed, under a new and fundamentally different neural regime.
