NATURE’s two-part special Dogs That Changed the World tells the epic story of the wolf’s evolution, how “man’s best friend” changed human society and how we in turn have radically transformed dogs. From the tiniest Chihuahua to the powerful and massive English Mastiff, modern domesticated dogs come in a bewildering array of shapes and sizes, with an equally diverse range of temperaments and behaviors. And yet, according to genetics, all dogs evolved from the savage and wild wolf — in a transformation that occurred just 15,000 years ago.

Part One: The Rise of the Dog Part Two: Dogs by Design.