Abstract:

Lip-smacking is a rhythmic facial gesture found across many primate species. It has been suggested that it derives from mouth movements associated with removing ectoparasites during grooming. It also has been implicated as an evolutionary precursor to the rhythmic consonant-vowel alterations that are universal features of human speech (MacNeilage 1998). Two recent lines of evidence support the latter proposal. First, Ghazanfar and colleagues (2012) have shown that the coordinated movements of lip-smacking in a macaque are more speech-like than the movements of chewing. Second, we have shown that geladas (Theropithecus gelada) produce a vocalized lip-smack (the ‘wobble’) that exhibits speech-like periodicity (Bergman 2013). Thus, vocalized lip-smacking may have been a critical step in the evolution of human speech. An evolutionary pathway from grooming, to lip-smacking, to rhythmic vocalizations, to speech provides a mechanistic twist on Dunbar’s vocal grooming hypothesis (1998). Language may, indeed, be long-distance grooming if the rhythm of speech derives from the mouth movements used in removing fleas from your friends.