A nice fairytale. And like all fairytales it doesn't need to be falsifiable to be worth telling.
>> If early Greek, Roman, Norse, and Chinese mythologies are anything to go by, the legends spun by early humans centre around an heroic human (almost always a man) who is pitted against an ugly, evil cruel monster with superhuman strength…
As a PoGO (Person of Greek Origin) my impression of our ancients' myths and legends is somewhat different. Yes, there was the Titanomachy and the Gigantomachy, but neither Titans nor Giants could be mistaken for "orcs" or "ogres"; the former were nightmare beasts with tentacles and the latter simply had a hundred hands. But most of our mythology is about the sexual lives of the gods, particularly Zeus' transformations to various animals that allowed him to sneak into maidens' beds (no accounting for taste) or the deeds of great heroes like Hercules, who however typically fight chimeric monsters (like the chimera itself, or the sphinx, or the harpies etc) or actual beasts (like the Erymanthian Boar or the Stymphalian Birds) rather than big burly monster men.
Where ancient Greek heroes fight beast-men, those are literally beast-men. The Minotaur is the child of a woman and a bull. The centaurs, who are not evil monsters, are a cross between man and horse. The sirens are depicted as birds with human heads. The Sphinx has a lion's body and a woman's head (there was clearly something going on with bestiality in ancient times). The cyclops Polyphemus and the giant Antaeus, slain by Heracles, are porbably the only examples of "orcs" that could be plausibly identified in Greek mythology. And even those are not very orc-like. Why would memories of Neanderthals be recorded in myths and legends as one-eyed giants?
Now the tale of Antaeus is an interesting one: Heracles wrestles him and keeps winning but everytime Antaeus bounces back. At length Heracles realises that Antaeus is drawing power from the Earth. He grabs him by the waist and crushes him preventing him from touching the ground, and so he wins. There is a clear symbolism there, of victory over an enemy that draws his strength from the land. But what does it mean? Who was this enemy? It doesn't have to be another species: a more ancient tribe that pre-dated the tale will do fine. It's an interesting question but we will never know the answer. As with the Neanderthals, that should not be license to imagine whatver we fancy, though.