Anecdote: Monkey Boy On Communication and Evolution

Driving home from Sam's Club, myself, MiL, and the boys in the car, all's quiet but for the oldies playing quietly on the radio and from the way back seat Monkey Boy ponders aloud: "Hmmm, the only reason humans evolved lips is because of our communication pattern." He went on to postulate on the subject, including a brief dissertation on the wide variety of animals who do NOT have lips, and still regularly survive in the wild, the only thing they lack being the more complex method of communication by which the human animal is distinguished.
His brother disagreed - although not as much in a passionate, science and observation based way, as in a 'here's an opportunity for an interesting debate' kind of a way - and the conversation became rather lively between them.
There was a rather heated tangent regarding whether the proof of Monkey Boy's theory was borne out by that fact that Disney has to add lips to animals that do not already possess them in its animated films, in order to make human speech visually plausible for them, but in the end a reluctant agreement was reached: mammals clearly require lips in order to nurse, however the rest of the animal kingdom appears to be getting along perfectly well without them, and the communication patterns of humans more likely evolved due the already extant lips, than the other way around.