This suggests that the difference between human and nonhuman brains may be far more complex and multi-faceted than simply an increase in extra neurons over and above the average primate or mammal trend. It starts with a nice bit about Hoover, the talking seal at the Boston aquarium. Vocalization is a complex function of this part of the brain. There is a lot of hard-wired vocalization. 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.