Atouk (Ringo Starr) is a scrawny little caveman, who gets pushed around by the others. He is expelled from the tribe by the chief, Tonda (John Matuszak), for going after the chief's curvaceous cave woman, Lana (Barbara Bach). Atouk becomes leader of a band of outcasts that include Lar (Dennis Quaid) and Tala (Shelley Long). Along the way, Atouk discovers fire, invents the spear and torch, invents cooking meat, invents music and learns to walk upright.
Lana falls in a river and floats downstream, to where Atouk rescues her. Tala becomes jealous, and leads Tonda's tribe back to take Lana. However, Tonda's tribe take all the women.
Atouk and his band, make weapons and armor. They return and defeat Tonda and his crew. As Atouk is proclaimed chief, Lana comes stand by him, thinking she will be his queen. He dumps her in a pile of dinosaur dung, and takes Tala's hand.
Thanks Joseph C!