Both Ron Perlman and Everett McGill suffered frostbite; luckily they were able to heal completely. Despite the working conditions, they both enjoyed making the film.
The woolly mammoths were played by circus elephants.
Everything in the film was shot live; there were no optical effects done in post production.
The language used by the cavemen, which comprises all of the spoken dialogue, was created by Anthony Burgess. Burgess is best known as the author of the novel and film Uhrwerk Orange (1971), and creator of the language, Nadsat, used in it.
The opening shot was intended to be just a test shot and wound up in the opening scene because it turned out better than expected.