btw, how is human speech not imitation? --PG

Vocabulary is imitation, but forming sentences isn't. "I saw three apples riding a truck to Texas yesterday." That sentence possibly has never been spoken before in the history of the world. We use patterns to create and to understand sentences. Animals imitate the sounds, or associate the sounds with a single concept in a one-to-one sort of way at the very most. Our language rules are much more complex, and they allow us to create and understand an infinite number of combinations.