I wish there was any way to know when language was developed in (proto?) humans. Our complex grammar is pretty unique in the animal kingdom, and it's clearly linked to our cognition. You can get pretty far with mere vocabulary (just look at the great apes), but once you get into the world of words modifying words and recombining into sentences, you have an absolute explosion of expressible ideas.

When did that happen? IMO, it's pretty clear the Chompsky school is at least partially correct in that we have biological hardware for grammatical language. So we've probably had language as long as we've been homo sapiens. Neanderthals probably spoke, too. But what about Homo Erectus? Australopithecus?