1.Introduction While examining the evolution oflanguage it is advantageous to study the evolution of speech independently.While speech is the default modality of language, language has more than one meansof transmission and therefore when examining language evolution it isworthwhile examining the evolution of the differing modalities and what makesthem special to humans. The evolution of speech can be broken down into anumber of parts: the evolution of speech production and articulation, whichinvolves exploring the changes in the vocal tract and neural control ofarticulators; the ability for vocal learning and imitation, which is overtlyseen in children learning language; and the evolution of speech perception,which involves examining changes to the auditory system. The aim of this essay is to explorethe human capacity for speech production and perception in regards to itsunique properties and the selection pressures which lead to their evolution.
Toachieve this aims the essay adopts the following structure: section two dealswith the evolution of the vocal tract in comparison to our common ancestors; sectionthree explains the changes in neurological control which aid speecharticulation; section four looks toward vocal imitation and how this plays arole in speech production and perception; finally section five examines thelinks between production and perception and how speech perception has evolved. 2.Vocal Tract Changes 2.1Formants Argued to be one of the mostimportant distinguishing features of human vocalization is the use of formants.When looking at both human and nonhuman primate vocalisations, one of thelargest differences seen is that humans rely heavily on formants for acousticproduction (Fitch 2000: 260).
Formants are best described by Gamba, Torti,Colombo and Giacoma (2012: 289) as the acoustic frequency peaks that areproduced by a spectrogram when recording speech. These peaks correspond withthe shape of the vocal tract during speech production. When the airflowvibrates through the vocal tract it is influenced by its shape and length. Thediffering formant frequencies produced equate to the different sounds producedby the different articulators in the vocal tract.