You have to think that there were breakthroughs in communication technology — not just language in general but possibly also one individual who happened to be good at explaining things, either before or after language, who both taught more people, but also taught them how to teach — that led to step changes in technology.
This was at least 200k years before the advent of speech if you go by the hyoid bone evidence.
I would consider this evidence that language predates human vocalizations. We already know deaf children will invent signs and gestures to communicate, and language not dependent on a hyoid bone. Do we have any way of dating the relevant neural structures through genetics?