The forgotten role of consonant-like calls in theories of speech evolution.

Ackermann et al. provide an informative neurological road-map to primate call communication. However, the proposed model for speech evolution inadequately integrates comparative primate evidence. Critically, great ape voiceless calls are explicitly rendered unimportant, leaving the proposed model deprived of behavioral feedstock and proximate selective drivers capable of triggering the neurological transformations described by the authors in the primate brain.