A 27-word "caveman language" was created for this film, supposedly drawing on Phoenician, Latin and Sanskrit sources. Some of the key words in this language are "Neecha", meaning "Stop" or "Come back"; "zak", meaning "gone" or "left"; "Akita", meaning "Look" or "See"; "neecro", meaning "bad" or "evil"; "m'kan", meaning "kill" or "killed"; "mata", meaning "dead"; "Yo Kita", meaning "Go".
Victoria Vetri revealed in a 1984 interview that the original UK version of the film contained nudity. The nude scenes included Tara and Sanna making love in a cave, Tara and Sanna skinny-dipping in a lake and Tara taking off Sanna's clothes on the beach. This uncut UK version has since been officially released on home video (i.e., DVD and Blu-ray) in the U.S. by Warner Archive.
Hammer's publicity department worked with Playboy magazine to produce a nude photo spread of Victoria Vetri showing more flesh than she was allowed to show in the U.S. version of the film.
Although the film was finished in 1968, Jim Danforth's stop-motion animation special effects were not yet ready. When the film premiered in 1970, the wait turned out to be worth it after all, since it was nominated for an Academy Award for Best Special Visual Effects.
Originally the film was to include a Tyrannosaurus, but Sir James Carreras, the very conservative studio head of Hammer, ordered Val Guest and Jim Danforth to remove this dinosaur from it because he thought its posture imitated the stereotypical posture of gay men.