[custom_adv] The dog and the extant gray wolf are sister taxa as modern wolves are not closely related to the wolves that were first domesticated, which implies that the direct ancestor of the dog is extinct. [custom_adv] The dog was the first species to be domesticated and has been selectively bred over millennia for various behaviors, sensory capabilities, and physical attributes. [custom_adv] Their long association with humans has led dogs to be uniquely attuned to human behavior and they are able to thrive on a starch-rich diet that would be inadequate for other canid species. Dogs vary widely in shape, size and colors. [custom_adv] The origin of the domestic dog is not clear. It is known that the dog was the first domesticated species. The domestic dog is a member of the genus Canis (canines), which forms part of the wolf-like canids, and is the most widely abundant terrestrial carnivore. [custom_adv] The closest living relative of the dog is the gray wolf and there is no evidence of any other canine contributing to its genetic lineage. The dog and the extant gray wolf form two sister clades, with modern wolves not closely related to the wolves that were first domesticated. [custom_adv] The dog and the extant gray wolf are sister taxa as modern wolves are not closely related to the wolves that were first domesticated, which implies that the direct ancestor of the dog is extinct.