It's 3.5 million years ago and in East Africa a remarkable species of ape roams the land. Australopithecus afarensis has taken the first tentative steps towards humanity by standing and walking on two legs.

This film follows a close-knit troop of afarensis, and in particular, Lucy and her young infant. Led by a strong alpha male, there is harmony in their lives. They sleep high in the trees and spend most of the day foraging for food. But then tragedy strikes. While drinking from a nearby river, a lone crocodile sneaks in unnoticed and catches the alpha male unawares.