Humans began to rapidly accumulate technological knowledge 600k years ago

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?

Quite a lot of humans don't think in language, or do only some of the time, see e.g. https://www.iflscience.com/people-with-no-internal-monologue..., https://www.livescience.com/does-everyone-have-inner-monolog..., https://www.bustle.com/wellness/does-everyone-have-an-intern....

There are also humans who can’t conjure up an image in their head. Mozilla cofounder wrote a fairly famous piece about his own experience.

https://www.theverge.com/2016/4/25/11501230/blake-ross-cant-...

If there are people who can’t picture and people who don’t have an inner dialogue, I think it lends more credence to the idea that we don’t have free will and are just a bunch of chemicals controlling our behavior. It also makes you think about consciousness and whether it’s even real.