The domestic dog (Canis lupus familiaris or Canis familiaris) is a domesticated canid which has been selectively bred over millennia for various behaviours, sensory capabilities, and physical attributes.
Although initially thought to have originated as an artificial variant of an extant canid species (variously supposed as being the dhole, golden jackal, or gray wolf), extensive genetic studies undertaken during the 2010s indicate that dogs diverged from an extinct wolf-like canid in Eurasia 40,000 years ago. Being the oldest domesticated animal, their long association with people has allowed dogs to be uniquely attuned to human behavior, as well as thrive on a starch-rich diet which would be inadequate for other canid species.
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 impact on human society has given them the sobriquet, "man's best friend".
In China and South Vietnam dogs are a source of meat for humans.