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

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

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?