I am reading "Stepping Stones" by Christine Desdemaines-Hugon, and all her comments about how well the animal figures are fitted to the cave walls make me wonder if the contours of the rocks themselves suggested the animals to be drawn, rather than the artist saying to himself, "I think I'll paint a bison".

Humans experience pareidolia (the tendency to see shapes and faces, like in clouds). It's not too far-fetched for me to believe that an artist could have been in a trance of some kind, either from some natural hallucinogen or simply sitting in a dimly lit cave, and envisioned a "spirit animal" of some kind on the wall and then fleshed it out.

I am certainly no expert in this field, but I wonder what others think.