I'm talking about the loincloth-wearing, wooden club-wielding, yabba-dabba-dooing cavemen we see in fiction all the time. Is there any historical evidence that these sorts of people were real?
Additional question: is the "caveman language" ("chaka chaka gunka lunka dunk") based on any real languages like PIE?
Your use of the word 'prehistoric' in your question would suggest that you are asking in the wrong subreddit. I suggest you crosspost to /r/askanthropology instead.
Evidence exists to suggest that Neanderthals and archaic humans did wear animal skins and used clubs and other weapons like the atlatl or flint napped arrows. Plenty of archaeological evidence shows that ancient people did live in caves. How they behaved is mostly speculation but overall the basic idea of the caveman is probably roughly accurate.