Comment by OskarS

The classic example which I think you’re referring to is Nicaraguan Sign Language, which developed organically in Nicaraguan schools for deaf children where neither the children nor the teachers knew any other form of sign language. It’s a fascinating story, a complex fully developed language created by children. Seems to indicate that this is indeed a very inate capability among humans in larger groups: https://en.wikipedia.org/wiki/Nicaraguan_Sign_Language