The human hands, face, and vocal machinery have evolved as finely differentiated parts as compared to other primates due to the two phenomena that includes child development and computational modeling. Infants imitate face and hand action as well as speech. All three modalities may share a common evolutionary path to organ differentiation through imitation. Facial imitation is unique among the three because infants can neither see the face they feel nor feel the face they see, so that imitation must be mediated by an intermodal representation. Language, spoken or signed, evidently requires an integral anatomical system of discrete, independently activated parts that can be coordinated to effect rapid sequences of expressive global action. Consonants are specified by acoustic trajectories, formed by gestural combinations of varying degrees of complexity. Lindblom's proposed a modified dispersal algorithm to predict consonant-vowel (CV) syllable trajectories by means of a cost/benefit ratio (articulatory cost/perceptual discriminability) summed and minimized over a system of syllable trajectories such as might appear in a small lexicon. Lindblom's work offers the most comprehensive computational model so far available of how systems of discrete gestures, phonemes, and syllables may have emerged by self-organization under perceptuomotor constraints from an evolved vocal tract.
Peter F. MacNeilage
This article focuses on the evolution of phonology over the years. The most comprehensive investigation of the innateness hypothesis in phonology is that undertaken by Mielke regarding the common claim that there is a small finite set of universal innate distinctive features that can describe the sound patterns participating in what are called phonological processes of all languages. He points out that the multiple sounds often participate in the same sound pattern. When a group of these sounds exhibits the same behavior it is often the case that these sounds are phonetically similar to each other. This type of grouping of sounds is termed a natural class. Syllabic “sonority” is considered to be an innate mental principle revealed by the fact that the loudest sound in a syllable is the vowel, and sonority then tends to decrease as the distance from the vowel of a preceding or a following consonant in the same syllable increases. The pattern can be attributable to peripheral biomechanics rather than mental structure. The concept of “markedness” is considered to involve another innate mental principle. The discipline of phonology has contributed an enormous amount of valuable information about the sound patterns of language.
This article raises an important question that asks whether the vocal capacities of great apes have been underestimated or not. Considerable research effort has been dedicated to vocal communication in primates, and has revealed communicative and cognitive traits in non-human primates that have relevance for language evolution. The vast majority of vocal communication studies to date have, however, focused on monkey species. In contrast to both research into monkey vocal communication and research on other aspects of great ape behavior and great ape vocalizations has been surprisingly limited. This relative paucity of information on great ape vocal behavior has serious consequences for the understanding of language evolution. First, given that apes outperform monkeys on many cognitive tasks, further research on great apes may reveal that they use their vocalizations in a more sophisticated way than monkeys, possibly demonstrating more commonalities with humans. This article refers to mammals such as chimpanzees and orangutan. Chimpanzee barks are also produced in a context-specific manner, indicating they have the potential to function referentially. Crockford and Boesch found that wild adult male chimpanzees produced bark variants in response to snakes, and whilst hunting. These barks were sometimes combined with other calls or drumming and when produced in conjunction with other signals, they were highly context specific. Playback experiments are now required to assess whether recipients extract meaningful information from these context-specific calls. Many issues need resolving, and numerous areas require more systematic investigation. In particular, the issue of the degree of volition and intentionality that drives call production in great apes must be addressed, as this currently represents a chasm between human and non-human primate vocal communication.