Birds are better than mammals at speech because of flight related modications to the breathing apparatus. Mammals manipulate the larynx, birds the syrinx. Visceral control in mamals is replaced by skilled motor control in birds. Cetaceans use blowholes, still another mechanism, to produce controlled vocalization. Most mammals run facial control on auto-pilot.
Primates have much more voluntary motor control of face.
Lots of stuff about humans uniquely vocalizing on exhalation. Infants babble a lot because it is easy for them to do. Chapter ends with claim language started with Homo habilis. Unsubstatiated at this point except for brain size arguments. Lots of stuff on prefrontal function mapping and various effects of prefrontal damage.