Despite great variation, all domestic dogs, as well as their common ancestor, the gray wolf, have virtually identical genes. How can science explain their incredible diversity?

From the huskies of the frozen north to the basenjis of the Congo River basin and the golden retrievers in America's backyards, dogs have carved a niche for themselves in every human society. How did this unique relationship develop? What can the latest breakthroughs in genetics reveal about dog origins and breeding? And can dog sociologists and psychiatrists unravel the puzzling, lovable and often maddening quirks of dog behavior? Despite wide variation, all domestic dogs, as well as their common ancestor, the gray wolf, have virtually identical genes. How can science explain this incredible diversity? NOVA visits state-of-the-art dog labs where the latest developments in genetic mapping and even cloning are in the air. Along the way, breeders and dog experts, as well as scientists, help explore the bond people share with these remarkable animals, seeking insights into the future of mankind's oldest and closest relationship with another animal species.