Claim: Dog have been selectively bred over millennia.

The domestic dog -LRB- Canis lupus familiaris or Canis familiaris -RRB- is a member of genus Canis -LRB- canines -RRB- that forms part of the wolf-like canids , and is the most widely abundant carnivore . The dog and the extant gray wolf are sister taxa , with modern wolves not closely related to the wolves that were first domesticated . The dog was the first domesticated species and has been selectively bred over millennia for various behaviors , sensory capabilities , and physical attributes .   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 colours . Dogs perform many roles for people , such as hunting , herding , pulling loads , protection , assisting police and military , companionship and , more recently , aiding handicapped individuals . This influence on human society has given them the sobriquet `` man 's best friend '' .