Renowned BBC wildlife filmmaker David Attenborough presents the most diverse group of animals to ever live on Earth: the mammals. From the little mouse to the gigantic blue whale, from the slow sloth to the lightning-fast cheetah and from the unattractive naked mole-rat to the adorable human baby, they're all covered. He tells the story of the more than 4,000 species that survived the dinosaurs, occupying the last corner of the earth and developing the most complex brains in the animal kingdom.