ONE MILLION YEARS B.C.

Men of the dark-haired Rock Tribe, led by chief Akhoba, who is accompanied by his rivalrous sons, Tumak and Sakana, capture and kill a warthog and return to share it with the rest of the tribe. Tumak and Akhoba fight over the meat, and Akhoba banishes Tumak to the harsh desert. After surviving several encounters with various prehistoric creatures, Tumak collapses on a remote beach and is spotted by Loana and other women of the fair-haired Shell Tribe. Joined by some of the men from the tribe, Loana rescues Tumak from an Archelon which is driven into the sea. Tumak is taken to the Shell Tribe's village where he discovers they are more civilized and advanced than the Rock Tribe. Back at the Rock Tribe, Sakana tries to seize power by killing Akhoba. Akhoba survives, but is a broken man as Sakana becomes the new leader.

With the Shell tribe, Tumak rescues a small girl from an attack by an Allosaurus, endearing him to Loana. However, Tumak is banished from the village after he fights Shell Tribe member Ahot for possession of the spear Tumak used to fight the creature. Loana decides to accompany Tumak, and Ahot surrenders the spear to Tumak in a gesture of good will. Tumak, with Loana in tow, wanders back to the Rock Tribe camp, but again, there are altercations, including witnessing an epic fight between a Triceratops and a Ceratosaurus. The most dramatic fight is between Tumak's current love interest Loana and his former lover Nupondi. Loana wins the fight but refuses to strike the killing blow, despite the encouragement from the other members of the tribe. Sakana resents Tumak's and Loana's attempts at incorporating Shell Tribe ways into their culture. While the Rock Tribe is swimming, a female Pteranodon attacks and snatches Loana to feed her to her offspring. However, a Rhamphorhynchus intervenes and a fight ensues. Loana is dropped into the sea and makes it to shore. At first, Tumak mistakenly believes Loana is dead, but they are soon reunited.

Sakana leads a group of like-minded fellow hunters in an armed revolt against Akhoba. Tumak, Ahot and Loana, and other members of the Shell Tribe arrive and join the fight against Sakana. In the midst of the battle, a volcano suddenly erupts. Members of both tribes are killed by either the effects of the volcano, or by their attackers. Sakana is speared to death and Akhoba is crushed by falling rock. Tumak, Loana, and the surviving members of both tribes emerge from the desolation and jointly set off to find a new home, with Tumak as the new leader.