There's plenty of ways to communicate complex ideas without using complex language, as long as you have sufficient time to interact. Skills can be taught using demonstration, imitation, and correction; ideas can be drawn or acted out.
What language enables, in my view, is accurate communication through intermediaries. It makes a lot of difference whether you need to supervise someone through all the ways that cooking on leather can go wrong versus richly explaining those same failure modes and how to avoid them. The former pretty much prescribes that most complex knowledge will stay within a tribe or a close community, whereas a rich vocabulary allows knowledge to spread readily among trade routes.
Right, it’s not like people born deaf are just completely useless as humans. Just like we have sign language and there is a whole concept of body language alone is enough to show it would be possible for them. We have people like Helen Keller who existed.
In Jean M Auel’s Earths Children books the Neanderthals communicated via hand gestures and vocalizations.
What language enables, in my view, is accurate communication through intermediaries. It makes a lot of difference whether you need to supervise someone through all the ways that cooking on leather can go wrong versus richly explaining those same failure modes and how to avoid them. The former pretty much prescribes that most complex knowledge will stay within a tribe or a close community, whereas a rich vocabulary allows knowledge to spread readily among trade routes.