<P> What was significant in this study was the observation that the changes in skull architecture that correlate with reduced aggression are the same changes necessary for the evolution of early hominin vocal ability . In integrating data on anatomical correlates of primate mating and social systems with studies of skull and vocal tract architecture that facilitate speech production, the authors argue that paleoanthropologists to date have failed to grasp the important relationship between early hominin social evolution and language capacity . As they write: </P> <P> In the paleoanthropological literature, these changes in early hominin skull morphology (reduced facial prognathism and lack of canine armoury) have to date been analysed in terms of a shift in mating and social behaviour, with little consideration given to vocally mediated sociality . Similarly, in the literature on language evolution there is a distinct lacuna regarding links between craniofacial correlates of social and mating systems and vocal ability . These are surprising oversights given that pro-sociality and vocal capability require identical alterations to the common ancestral skull and skeletal configuration . We therefore propose a model which integrates data on whole organism morphogenesis with evidence for a potential early emergence of hominin socio - vocal adaptations . Consequently, we suggest vocal capability may have evolved much earlier than has been traditionally proposed . Instead of emerging in the Homo genus, we suggest the palaeoecological context of late Miocene and early Pliocene forests and woodlands facilitated the evolution of hominin socio - vocal capability . We also propose that paedomorphic morphogenesis of the skull via the process of self - domestication enabled increased levels of pro-social behaviour, as well as increased capacity for socially synchronous vocalisation to evolve at the base of the hominin clade . </P> <P> While the skull of A. ramidus, according to the authors, lacks the anatomical impediments to speech evident in chimpanzees, it is unclear what the vocal capabilities of this early hominin were . While they suggest A. ramidus - based on similar vocal tract ratios - may have had vocal capabilities equivalent to a modern human infant or very young child, they concede this is obviously a debatable and speculative hypothesis . However, they do claim that changes in skull architecture through processes of social selection were a necessary prerequisite for language evolution . As they write: </P> <P> We propose that as a result of paedomorphic morphogenesis of the cranial base and craniofacial morphology Ar . ramidus would have not been limited in terms of the mechanical components of speech production as chimpanzees and bonobos are . It is possible that Ar . ramidus had vocal capability approximating that of chimpanzees and bonobos, with its idiosyncratic skull morphology not resulting in any significant advances in speech capability . In this sense the anatomical features analysed in this essay would have been exapted in later more voluble species of hominin . However, given the selective advantages of pro-social vocal synchrony, we suggest the species would have developed significantly more complex vocal abilities than chimpanzees and bonobos . </P>

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