On a small number of official lists.
-- On one official list.
Clue #1: The cast credits for this film feature many character names, but in the movie itself I doubt any character names are mentioned.
In this movie, there are a lot of characters, but if I asked you for their names right before the end credits, you'd say you had no idea (unless, perhaps, you're extremely observant).
-- Characters do speak some sort of languages, but it mostly just sounds like grunts and occasional gibberish. But at the end credits, the various tribes have names and almost all the individuals have names.
Clue #2: The missionary represents civilization, doggy-gone it!
-- The culturally more advanced Cro Magnon woman convinces the Neaderthal man to stop clumsily and forcibly taking her from behind, and instead teaches him the missionary position. Humankind moves forward, and, well, the doggy position is gone.
Clue #3: They say if you can't laugh at yourself now and then ... well, he couldn't, ever. He and his friends just never got any jokes at all. It took a head wound to change all that.
-- The Neanderthal men have no concept of laughter. But when a rock is dropped on one of their heads, drawing blood, the Cro Magnon woman laughs and laughs, and eventually the three Neanderthal men 'get it' and start to laugh, too.
Clue #4: A grown man watches a boy do something most Boy Scouts learn to do, and the man's life is changed forever. So are the lives of everyone he knows.
-- The Neanderthal protagonist watches a Cro Magnon boy make fire using sticks, kindling, and friction. Now he knows he can save his tribe and never lose the fire again.
Clue #5: The main romance in the film is not just inter-racial; it's inter-specific.
-- It is love, and procreation, between a Neanderthal and a Cro Magnon.