What are your thoughts about extending the history of pictograms back to cave paintings? I understand that the word “pictogram” as you are using it here has a very definite meaning and I am being more lose with that meaning, but cave paintings, as best archaeologists can tell, share a lot in common with icons and pictograms. They were not meant to be realistic depictions of animals but more symbolic/spiritual representations to either communicate between tribe members or to exert some supernatural control over animals (to have a good hunt).
I know, this is purely speculative since experts don’t know for sure what the creators of cave paintings intended. I’m curious what your thoughts are because I have always considered cave paintings to be the first icon-like art of humans. It seems that some attempts at early written language have been around as long as humans cooperating and using tools.