Chapter 2: The First Frontier

For billions of years, land on Earth was uninhabitable. But in the seas, predation allowed species to thrive before — and after — two mass extinctions.

Chapter 3: Invaders of the Land

Sprawling moss, towering trees, flying insects, limbed amphibians: Early species vied for domination as the land went from hostile to hospitable.

Chapter 4: In Cold Blood

After Earth's third mass extinction, mammals' surviving ancestors ruled the supercontinent Pangea. But lizards soon ushered in the age of reptiles.

Chapter 5: In the Shadow of Giants

The formation of continents with varied environments allowed for an explosion of biodiversity — and turbo-charged the evolution of mighty dinosaurs.

Chapter 6: Out of the Ashes

The dinosaurs met their end with a cataclysmic asteroid impact. Rising from the ashes, birds reinvented themselves into a dynasty 10,000 species strong.

Chapter 7: Inheriting the Earth

Emerging from the dinosaurs' shadows, mammals went from underdogs to global power, with game-changing adaptations that would conquer land, air and sea.

Chapter 8: Age of Ice and Fire

As the Ice Age thawed, humans rose above the rest. But the possibility of a sixth mass extinction now looms: Has our ingenuity caused our downfall?