> I in particular am not a huge fan of the infographic[0] that uses the same image asset to refer to a spiral, box, sun, dots, etc... for entire continents, for all recorded history.
That infographic has bigger problems.
>> The similarities suggest the marks are more than just random scribbles
Except here are some of "the marks":
x # |||| * 一 (hand)
...
...that the people who drew a hand had hands.
Every single one of the other marks -- and the hand mark, too -- are things you could expect to find if you gave a small child some paper and crayons.
Worth noting that the hand “mark” is actually just a handprint—put hand on wall, spit pigment, done. To continue your comparison, it is essentially finger painting.