I think answer is near. Just listen animals. Birds, mammals, reptiles, insects all speak different which we can't understand it's grammar, even we think they don't speak. We assume they just make simple anger, threat, alarm, invitation sounds without intelligence.

Also a word can be pronounce in infinitely different. It means a whole language can be consist of only one word's different pronounce.

Furtermore, there are no need to sounds to form a language. Colors, light, pressure, scent can also be ways to communicate.