Near the end of the Tertiary Age, the narrative follows an emergent human tribe called the Ammi as they separate from apes and forge early social institutions. Through episodic adventures—kidnapping and rescues, expeditions from Cocoanut Hill, and battles in Alligator Swamp—the story dramatizes the crude origins of tools, fire, clothing, weapons, building, government, religion, commerce and the arts. Characters such as Sosee, Koree and elders like Gimbo negotiate conflicts with neighboring apes and the natural world, while scenes depict survival, technological improvisation, social organization, and moral reflection, blending scientific speculation about prehistoric life with humor and illustrative set pieces.