David Attenborough has undertaken nothing less than a history of nature, from the emergence of tiny one-celled organisms in the primeval slime more than 3,000 million years ago to apelike but upright man, equally well adapted to life in the rain forest of New Guinea and the glass canyons of a modern metropolis. Told through an examination of animal and plant life today - with occasional juxtapositions of extinct fossil forms to reveal the origin of living creatures - "Life on Earth" is an astonishing pageant of life, with a cast of characters drawn from the whole range of living animals the world over.