The year is 196303 BC. A group of cavemen rises from the mud, and the first thing on their minds is finding something to eat. After two unsuccessful attempts, the group decides to eat one of their own. Suddenly, the men meet women, but don't know how to Sexual intercourse to them. The elder of the men sees a pair of stegosaurus performing Doggy style, which inspires the elder to do the same thing with one of the women. Nine months later, that same woman is pregnant with two boys, Ah and O. The cavemen like Ah, but are frightened by O and abandon him. Meanwhile, a brontosaurus abandons one of her eggs. Both O and the baby brontosaurus Igua meet, and instantly become friends.