- Kenneth Branagh - Narrator: [about Earth's sustenance of life] But who would inherit this blue planet?
- Kenneth Branagh - Narrator: [about the monsters] Amongst them were our own earliest ancestors, whose survival would decide whether we humans would exist at all!
- Kenneth Branagh - Narrator: This is our planet, five hundred and thirty million years ago. Nothing yet lives on land, but in the ocean, it's a different story.
- Kenneth Branagh - Narrator: He may not look like you or I, but this odd fish is becoming the blue print for our own bodies.
- Kenneth Branagh - Narrator: Land at this time is like an alien planet. It's a barren expanse of roasting rock hotter than the Sahara. The air would be toxic to us: it has much less oxygen, and three hundred times more carbon dioxide than today.
- Kenneth Branagh - Narrator: It is the arthropods, and not our ancestors, who have taken the first momentous steps out of the sea onto dry land.
- Kenneth Branagh - Narrator: Brain has triumphed over brawn, and soon, they won't be such soft targets. Evolution starts to give them weapons to fight back.
- Kenneth Branagh - Narrator: They're the first ever true vertebrate landlubbers. The very first reptiles. But as they move inland, they'll face an ancient enemy, more deadly than ever before: the arthropods are back!