What's really amazing is that they still don't know the "why" other than some interesting speculation: religious purposes, places for psychadelic trips, "the creation of surpluses in some kind of hierarchy."

Coincidentally, last week the local public television station was replaying a very old program of Bill Moyers interviewing Joseph Campbell, who died in the late 80s and was known for studies of mythology. He had visited Lascaux, and believed that it was used for coming of age ceremonies:

JOSEPH CAMPBELL: The message of the cave is of a relationship of time to eternal powers that is somehow to be experienced in that place. Now, I tell you, when you’re down in those caves, it’s a strange transformation of consciousness you have. You feel this is the womb, this is the place from which life comes, and that world up there in the sun with all those … that’s a secondary world: this is primary. I mean, this just overcomes you. ...

Now, what were these caves used for? The speculations that are most common of scholars interested in this, is that they had to do with the initiation of boys into the hunt. You go in there, it’s dangerous, it’s very dangerous. It’s completely dark. It’s cold and dank. You’re banging your head on projections all the time, and it was a place of fear. And the boys were to overcome all that, and go into the womb of the earth. And the shaman, or whoever it was that would be helping you through, would not be making it easy.

BILL MOYERS: And then there was a release, once you got into that vast, torchlit chamber down there. What was the tribe, what was the tradition trying to say to the boy?

JOSEPH CAMPBELL: That is the womb land from which all the animals come.

BILL MOYERS: I see.

JOSEPH CAMPBELL: And the rituals down there have to do with the generation of a situation that will be propitious for the hunt. And the boys were to learn not only to hunt, but how to respect the animals and what rituals to perform, and how in their own lives no longer to be little boys but to be men. Because those hunts were very, very dangerous hunts, believe me, and these are the Original men’s rile sanctuaries, when: the boys became no longer their mothers’ sons, but their fathers’ sons.

https://billmoyers.com/content/ep-3-joseph-campbell-and-the-...

'They take you out of life, out of time': a journey into Spain's cave paintings