For nearly 4 billion years, the continents of Earth were a lifeless wasteland. But beneath the sea, our planet was teeming with life. Many strange creatures evolved, from eel-like conodonts to voracious cephalopods, until nearly all life was wiped out in our planet’s first mass extinction.
In the first episode, the team uncover the hidden lives of three iconic animals. In the Kalahari Desert the team put cameras on wild meerkats for the first time, allowing scientists to finally understand what these miniature mammals get up to underground. Heading to Cameroon, Gordon works with scientist Mimi Swift, who is desperate to understand whether Kimbang, a four-year-old orphan chimp, has the skills she needs to be able to join a chimp family living wild in the forest. Leaving Africa for Argentina, the team have penguins carry tiny cameras far out to sea on an epic journey of up to 300 kilometres (200 miles). For the first time, scientists are able to see the tactics these charismatic characters use to catch their prey.
Coral reefs are home to a quarter of all marine species. Survival in these undersea mega-cities is a challenge with many different solutions. A turtle heads to the reef's equivalent of a health spa - but she must use trickery to avoid the queue. A remarkable Grouper uses the fish equivalent of sign language to collaborate with an octopus, flushing their prey out of hiding holes. A metre-long, ferocious-jawed Bobbit Worm hides in its tunnel. Monocle Bream retaliate by squirting water to expose its sandy lair.
This programme looks at the evolution of fish. They have developed a multitude of shapes, sizes and methods of propulsion and navigation. The sea squirt, the lancelet and the lamprey are given as examples of the earliest, simplest types. Then, about 400 million years ago, the first back-boned fish appeared. The Kimberley Ranges of Western Australia are, in fact, the remnants of a coral reef and the ancient seabed. There, Attenborough discovers fossils of the earliest fish to have developed jaws. These evolved into two shapes of creature with cartilaginous skeletons: wide ones (like rays and skates) and long ones (like sharks).
In this final episode we complete our journey, travelling back from the March equinox to the end of June. Kate Humble is in the Arctic at a place where spring arrives with a bang, whilst Helen Czerski chases a tornado to show how the earth's angle of tilt creates the most extreme weather on earth.