In my head canon, some Neanderthal managed to find acceptance in Homo sapiens societies through prodigious feats of strength or bravery.

IIRC, Neanderthal were far stronger than us.

Mind you, could be that they're where folk memory of dwarves arises, short, strong, like living underground.

Maybe elves were Homo floriensis?

I love speculating like this because it's entirely unprovable, much like evolutionary psychology.