One Million B.C. (1940)

Starring Victor Mature, Carole Landis, Lon Chaney, Jr., Conrad Nagel, John Hubbard
Directed by Hal Roach & Hal Roach, Jr.
(actor & director credits courtesy IMDB.com)

A caveman from a hostile tribe journeys to another tribe's territory, where he meets a beautiful woman who teaches him the gentler ways of her people.

I was surprised to find how entertaining this film is, as for me, caveman movies often get bogged down by their lack of dialogue, and as a consequence are sometimes difficult to follow.  That's not the case here, with the filmmakers embracing a simple story and not calling on anything too complex for their actors to portray besides basic emotions.  The movie has almost a light-hearted tone, accompanied by a whimsical music score, despite some violent scenes.  The special effects combine men in dinosaur suits along with giant rear projections of lizards and elephants in wooly mammoth coverings to provide the prehistoric creatures of the film.  Although scientifically inaccurate, these are well-done effects that according to IMDB earned the film an Academy Award nomination, and were borrowed by numerous films well into the 1960s.