Only by misconstruing the term performative are the authors able to argue that males surpass females in performative applications of language. Linguistic performatives are not costly displays of quality, and syntax cannot be explained as an outcome of behavioural competition between pubertal males. However, there is room for a model in which language co-evolves with the unique human life-history stage of adolescence.

Locke & Bogin's (L&B's) main thesis can be extended to the acquisition of the phrasal vocabulary in that the acquisition of much phrasal vocabulary combines the acquisition of linguistic knowledge with pragmatics and performance and in that the apprenticeship system for such learning begins to flower in adolescence.

In the first year of life, infants' utterances change from high-intensity crying to low-intensity acoustic sound strings, acoustically labelling the first word. This transition implies: (1) decoding of phonetic sounds, (2) encoding of phonetic sounds, and (3) a unique linking of an articulated sound to a specific object. Comparative, ontogenetic, and phylogenetic aspects are considered for multilevel selective pressures.

In this commentary, I ask three specific questions: (1) Why would a juvenile stage be maintained in humans? (2) What could be a satisfactory evolutionary scenario explaining the features of feminine speech? And (3), what could be the contribution of sexual selection in the elicitation of higher informational contents in communicative signals?

Critical factors that appear to encourage vocal development in humans are altriciality and long immaturity. Hominid infants appear to have evolved a specific tendency to use elaborate vocalization as a means of soliciting long-term investment from caregivers. The development of such vocal capacity provides necessary infrastructure for language development across human life history.

Of three types of evidence available to evolution theoristscomparative, continuity, and computationalthe first is largely productive rather than predictive. Although comparison between extant species or languages is possible and can be suggestive of evolutionary processes, leading to theory development, comparison with extinct species and languages seems necessary for validation. Continuity and computational evidence provide the best opportunities for supporting predictions.

The uniqueness of human cognition and language has long been linked to systematic changes in developmental timing. Selection for postnatal skeletal ossification resulted in progressive prolongation of universal patterns of primate growth, lengthening infancy, childhood, and adolescence. Language emerged as communication increased in complexity within and between communities rather than from selection for some unique features of childhood or adolescence, or both.

The social function of language, as exemplified by tonic communication, is certainly not restricted to our own species. An individual's cognitive mastering of its environment, moreover, is equally essential for understanding the nature of any language. In the absence of comparative data, it is premature to claim that language skills at a particular developmental stage are uniquely human.

The target article by Locke & Bogin (L&B) focuses on the evolution of language as a communicative tool. They neglect, however, that from infancy onwards humans have the ability to go beyond successful behaviour and to reflect upon language (and other domains of knowledge) as a problem space in its own right. This ability is not found in other species and may well be what makes humans unique.

Locke & Bogin (L&B) propose that humans are unique in possessing stages of childhood and adolescence. Arguments to the contrary include evidence for a similar and adaptive juvenile period in simians of slow growth, intense play and learning, and provisioning with solid food by adults. Likewise, simians as well as humans undergo a compensatory growth spurt during puberty.

The stormy development of vocal production during the first postnatal weeks is generally underestimated. Our longitudinal studies revealed an amazingly fast unfolding and combinatorial complexification of pre-speech melodies. We argue that relying on melody could provide for the immature brain a kind of filter to extract life-relevant information from the complex speech stream.

The finding of the same language deficit in half the members of the KE family is taken as suggesting that a specific allele (FOXP2) is normally involved in the development of language. Recent studies, however, question the exclusivity of FOXP2, and it is argued that the finding of a gene that disrupts language should not be taken as strong evidence for the existence of genes that underlie it.

Language, like other human traits, could only have evolved during one or more stages of development. We enlist the theoretical framework of human life history to account for certain aspects of linguistic evolution, with special reference to initial phases in the process. It is hypothesized that selection operated at several developmental stages, the earlier ones producing new behaviors that were reinforced by additional, and possibly more powerful, forms of selection during later stages, especially adolescence and early adulthood. Peer commentaries have provided opportunities to explain human life history more comprehensively, and to add details to our account of spoken language. We made no attempt to explain syntax in the target article, but we propose here that selection for vocal plumage may have increased our species capacity for utterance complexity, a development that would have benefited all levels of language.