The Shaman's Cape-Religion among the Neanderthals Glenn. I agree that fossil evidence can not prove intent. So by that standard we cannot prove ritual. But by that standard we can not prove intent of ritual by finding a phoenician idol.
People have statues of fish for lots of reasons.
We believe it to be evidence of ritual because they are us. When it comes to Neanderthals there is less certainty that they are us. There is lots of similarity between them and us in ritual activities. There is evidence in the form of the use of red-ochre by Neanderthals. Today red-ochre is used by primitive peoples as part of the body paint for their rituals.