So here's a really interesting article about what happens to bird songs when a bird is domesticated. Basically the song changes from something very constructed to something very unconstructed when a bird has been domesticated for a few generations. It's interesting, and they are applying what happened to these birds to what may have happened to our primate ancestors.
The hypothesis is that we are self-domesticated apes, and what this ends up meaning is perhaps why we have such a sophisticated language, and other primates do not, is because we took a few evolutionary steps backwards before going forwards. I don't really like using those terms, because in this sense backwards has a negative connotation, but I can't say I don't agree. It makes sense, and I can believe this really happened. I'd like to see more studies on this to confirm the hypothesis.