> We taught Koko the gorilla how to talk

I think you're overstating your case. "although the gorilla learned a large number of signs she never understood grammar or symbolic speech" - https://en.wikipedia.org/wiki/Great_ape_language#Koko

> humans that don't have language

Which humans are those? Language arises pretty spontaneously among humans even if they're deaf or blind - https://en.wikipedia.org/wiki/Nicaraguan_Sign_Language

Yet no amount of exposure will make a dog or ape understand language.

> There is, literally, a part of the brain that if you shut it off, you lose language.

You mean the entire left hemisphere?