For anybody into prehistoric abstract symbols who hasn't encountered this, "The Signs of All Times 1988" [1] is a super interesting study. Also very readable for the majority of us who are not in the field. Pairs nicely with Herzog's Cave of Forgotten Dreams [2] and any mid-tier Cabernet.
[1] https://www.jstor.org/stable/2743395
[2] https://en.m.wikipedia.org/wiki/Cave_of_Forgotten_Dreams
And just my two cents as an under-qualified former art history teacher...
It's fascinating and totally valid to try to analyze these symbols as proto-linguistic, but it can be even more interesting to imagine the cognitive roll these kinda of abstract symbols might have played outside the scope of language as we understand it.
Trying to imaging the structure of the mind and experiencing reality with a complete absence of language can be immensely mind-expanding, even just as a thought experiment. At least it was for me.
As we were taught in entoptic studies, these are not elements of a proto language, they are externalizations of the occipital/retinal that both reference the brain and reference space - together.
They are the basis for a spatial language of topological parts that have yet to be realized but does integrate with the plastic arts. ie are these the source of pictograms as language? Probably not. Is there are continuity with Kurgan or Chinese ideograms? We can't find them. Is there a continuity between counting tokens and alphabets? Yes, there's a stronger case for that.
https://pubmed.ncbi.nlm.nih.gov/23890291/