How did vocal behavior "take over" the gestural communication system?

In this commentary, I argue (i) that there are some peripheral homologies between the monkey and the human vocalization systems; (ii) that complex vocal learning can be achieved without need of a voluntary hand grasping circuit; and (iii) that in the monkey there are rudimentary circuits that can convey auditory information into Broca's region, via the "ventral pathway" but also via the arcuate or the superior longitudinal fasciculi.