It's not well established at all. Obviously Neanderthals were intelligent, but to what degree is a lot less clear. It's a hotly debated topic with lots of disa

It's not well established at all. Obviously Neanderthals were intelligent, but to what degree is a lot less clear. It's a hotly debated topic with lots of disagreement. Almost everything about Neanderthals is controversial. Take almost everything you read about Neanderthals that talks in absolutes with a grain of salt, because chances are a significant body of reasonable well-respected experts will disagree. The typical story is something along the lines of "well, there is some evidence, but it's not very strong, and it could mean a number of different things, and oh, it also could have been humans". With pre-historic humans we can reasonably safely operate on the assumption they were at least roughly like us, and take lessons from more recent hunter-gatherer groups, and things like that. But for Neanderthals you can't really do that because their behaviour and "sensibilities" could have been very different. It was bloody rude of them to go extinct before we had a chance to ask some questions.