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.
Theory: there are no humans without language. Consider: what language do you think in?
Indeed, there are two types of people in that regard, whose mind is blown (usually) that there is another type. One thinks in words, one has no words but a smooth stream of thought going.
That's wild - I am clearly the first sort, because I cannot imagine what "a smooth stream of thought" would even be if it were not expressed in words.
For what it's worth, I used to be certain that I thought in words too. Then I moved to a different country and used a second language often enough that I sometimes think in it. I then realized that there are periods where I think in neither my native language nor in my second language, even when I'm thinking. YMMV of course.