Billions of years ago, when life began, the surface of Earth was a very dangerous place to be. Searing temperatures scorched the land, noxious fumes belched from volcanoes and with no protective ozone shield, the sun's rays cooked anything that moved. Nothing could live here. But deep under the oceans, the seeds of life had already been sown. In the frozen depths of the deepest trenches, the first animals were born. Before long the oceans were alive with vast reefs of strange creatures, each trying out newly evolved solutions to the problems of living. They had the first shells, the first back bones, the first legs and the first teeth. They were the first swimmers, the first parasites and the first predators, some of which grew to immense sizes, even bigger than a man. Many died out, but the successful ones became the blueprints of all modern life on Earth, from the tiniest ant to the largest mammal — they were even the first ancestors of you and me. David Attenborough is synonymous with the Natural World. From bacterium to blue whale, he has seen it all for himself. But now he embarks on the journey he always wanted to make but never thought possible — a voyage back in time to see how the first animals evolved and how they lived. Recent discoveries at fossil sites around the world over the last twenty years have propelled our understanding of the first life forms to new heights and with the emergence of ground breaking ways of visualizing them, including state of the art CGI, Attenborough will finally realize his dream and see for himself the animals that laid the foundations for all life on Earth.