Language out of Music: The Four Dimensions of Vocal Learning

A growing consensus drawing on research in a wide variety of disciplines has, over the last fifteen years or so, argued the need to revisit Darwin's conjecture of 1871 that language may be descended from an existing, musical medium of communication that developed from animal calls. This paper seeks to examine, in an extension of Hockett's analysis of the design features required for linguistic communication, the nature of the acoustic information produced and perceived in human vocalisation, and to consider the anatomical and neural mechanisms on which these depend. An attempt is made to sketch an evolutionary chronology for key prerequisites of human orality. Cross‐species comparisons are employed to illuminate the role of four acoustic variables (pitch, duration, amplitude and timbre), viewing the potential for human vocal productivity from the perspective of animal communication. Although humans are the only species to combine entrainment to pulse with attunement to precisely‐tracked pitches, we also depend both for musical interaction and the production and perception of vowel sounds on precise and conscious control of the property of timbre. Drawing on, amongst others, Scherer's analyses of emotionally triggered sounds in a variety of species, and Fernald's presentation of the similarities of infant cries and adult production of infant‐directed speech in a variety of cultures and languages, a case is made for the instinctive components of human communication being more music‐like than language‐like. In conclusion, historical and comparative data are employed to outline the adaptive and exaptive sequence by which human vocal communication evolved. The roles of selective pressures that conform to different adaptive models are compared—natural selection, sexual selection, group selection—leading to the proposal that all of these must have played their part at different stages in the process in a ‘mosaic’ model consistent with the development of other human traits.