I think that if you were trying to decode one of those languages you would take the same approach and observe coordination behavior, “there is a deer to our left” -> tribe goes left.
You need to start somewhere. Maybe you would never be able to decode the non-functional communication without a Rosetta Stone or common language root.
The point is that at least some of language needs to cash out into a description of the physical world. I’d argue almost all of it, even in modern societies.
It's easy to start learning another language without an interpreter or dictionary, you just start with concrete objects and actions. The hard part is representing the sounds (phonemes), which are often quite different from the language the learner knows. It helps that there is a way of writing all the known sounds of all the studied languages (the IPA, which Wikipedia uses), and it's pretty rare these days that a "new" sound is found.
You need to start somewhere. Maybe you would never be able to decode the non-functional communication without a Rosetta Stone or common language root.
The point is that at least some of language needs to cash out into a description of the physical world. I’d argue almost all of it, even in modern societies.