The sentiment that it is impossible to think without writing is patently wrong. While it's an excellent tool, it takes an overly textual perspective and completely ignores the value of orality an memory in prehistory.

Modern culture has lost so many of our valuable cultural resources that we have completely forgotten that they even existed.

Oral cultures certainly had networked thought, Luhmann and others simply can't imagine how it may have worked. We're also blinded by the imagined size of societies in pre-agricultural contexts. The size and scope of cities and city networks makes the history of writing have an outsized appearance.

Further, we don't have solid records of these older netowrks, a major drawback of oral cultures which aren't properly maintained, but this doesn't mean that they didn not exist.