> These are entopics
Without a time machine, that opinion is no more valid than people keeping a consistent mapping and storytelling language by drawing in the dirt. There is evidence on both sides.
For example, the picture of the entrance stone on this page uses spirals:
Not so. As these are isolated occurring form constants popping up outside of any possible diffusion, their universality prior to symbolic or pictographic coherences indicate an interim state between expression and symbol.
The rush to claim these are a language is unsupported and is quite suspicious of a retrofitting that's prone to pseudoscience.
I would read Paleoperformance and Paleopoetics for discussions about pre-literate, pre-symbolic cultures from the archeological evidence.
Imposing intent or causality onto these is a bit bizarre.
The spirals from Newgrange. Those are indeed claimed to "resemble phosphenes" in Does the Nervous System Have an Intrinsic Archaic Language? which this person posted in another comment. They are neolithic, which is a very long way from paleolithic, not just in time but in development of ideas. The paper has another montage of images with the Gundestrup cauldron in it! That was made in the small hundreds AD. It's just a grab-bag of anything that looks shamanic to support the thesis "maybe they were tripping", about everybody everywhere throughout time, and yes, fair point, maybe they were tripping, it's worth bearing in mind. Also, maybe they were stupid. So what? Is this a solution to any problem?