Drawing on insight gleaned from 35 years of raising, training, and researching the behaviors of dogs worldwide, the authors explore in detail how dog breeds have evolved into their unique shapes and behaviors. Concentrating on five types of dogs - modern household dogs, village dogs, livestock guarding dogs, sled dogs, and herding dogs - they examine our canine companions from a unique biological viewpoint. Clearly points the way for dog lovers, therapists, veterinarians, and all others who deal with dogs to understand their animals from a fresh perspective. How did the domestic dog become a distinct species from the wolf? Why do different breeds behave differently? How can we improve the relationship between humans and dogs? Shows how dogs' different abilities depend upon the confluence of their nature and nurture; both genetics and the environment play equally key roles.