Lest anyone else be put off - the doodles are just one example of something not (or barely) visible without the new imaging techniques described. It's about finding new artefacts in an existing collection, not 'oh wow so weird an ancient human doodled something'.
I find it curious that archaeologists or historians (?) seem to take a lot of things like this so seriously and assume everything has some sort of symbolic meaning, rather than just some teenager scribbling on a page or painting his hand on the wall of a cave just 'because'.
If you have a gnome garden ornament on your shelf, no-one would seriously think you worship it, just that it looks nice. But this entire profession will call it a 'mysterious religious figure' etc.
Same with tattoos, ask any girl why they have a tramp stamp they'll say it looks 'cute' or something, these guys will call it 'symbolic'.
It's embarrassing.
Yes, it's definitely funny how they completely fail or refuse to consider this possibility. Humans weren't any different in 10 000 BC. Evolution doesn't work that fast.