It is the greatest story on earth - the development of life on this planet over three and a half billion years. The series which tells it took three years to make, involved one and a half million miles of travel, and includes some of the most beautiful, breathtaking and ambitious photography ever seen on television - including the unforgettable sequence in which its narrator, David Attenborough, meets a family of wild mountain gorillas. Thanks to the great richness of the natural world, it is still possible to illustrate all the crucial episodes in this story with living creatures. The fan-like marine organisms that were among the earliest multi-celled creatures; fish that developed the ability to breathe air and wriggled up on to land; birds that still retain claws in their wings like those of their reptile ancestors; and the platypus, a furry mammal that feeds its young with milk but lays eggs. In between these dramatic episodes, the series surveys the astonishing richness of surviving species belonging to each group in a pageant of breath-taking beauty that makes this series one of the great landmarks of British television.