Dogs share human households more intimately than any other animal, and this NOVA episode asks what centuries of living alongside us actually did to them. It traces the story back to wolves and the earliest domestication event, then follows how selective breeding over generations split one species into the huge range of shapes and temperaments seen in modern breeds. Researchers run dogs through behavioral tests that compare them with wolves and chimpanzees, checking whether dogs read human pointing and gaze in ways other animals cannot, and the film reports on brain and hormone studies looking for the biological changes domestication left behind in both species. Scientists appear on camera walking through their experiments and explaining what the results suggest about communication between dogs and people. The film treats the human-dog bond as a testable question rather than a given, using the science of domestication to explain why this particular partnership took hold so completely.