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The domestic dog (Canis lupus familiaris or Canis familiaris) is a member of genus Canis (canines) 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".
The term "domestic dog" is generally used for both domesticated and feral varieties. The English word dog comes from Middle English dogge, from Old English docga, a "powerful dog breed". The term may possibly derive from Proto-Germanic *dukkōn, represented in Old English finger-docce ("finger-muscle"). The word also shows the familiar petname diminutive -ga also seen in frogga "frog", picga "pig", stagga "stag", wicga "beetle, worm", among others. The term dog may ultimately derive from the earliest layer of Proto-Indo-European vocabulary.
In 14th-century England, hound (from Old English: hund) was the general word for all domestic canines, and dog referred to a subtype of hound, a group including the mastiff. It is believed this "dog" type was so common, it eventually became the prototype of the category "hound". By the 16th century, dog had become the general word, and hound had begun to refer only to types used for hunting. The word "hound" is ultimately derived from the Proto-Indo-European word *kwon-, "dog". This semantic shift may be compared to in German, where the corresponding words Dogge and Hund kept their original meanings.
A male canine is referred to as a dog, while a female is called a bitch. The father of a litter is called the sire, and the mother is called the dam. (Middle English bicche, from Old English bicce, ultimately from Old Norse bikkja) The process of birth is whelping, from the Old English word hwelp; the modern English word "whelp" is an alternate term for puppy. A litter refers to the multiple offspring at one birth which are called puppies or pups from the French poupée, "doll", which has mostly replaced the older term "whelp".
In 1758, the taxonomist Linnaeus published in Systema Naturae a categorization of species which included the Canis species. Canis is a Latin word meaning dog, and the list included the dog-like carnivores: the domestic dog, wolves, foxes and jackals. The dog was classified as Canis familiaris, which means "Dog-family" or the family dog. On the next page he recorded the wolf as Canis lupus, which means "Dog-wolf". In 1978, a review aimed at reducing the number of recognized Canis species proposed that "Canis dingo is now generally regarded as a distinctive feral domestic dog. Canis familiaris is used for domestic dogs, although taxonomically it should probably be synonymous with Canis lupus." In 1982, the first edition of Mammal Species of the World listed Canis familiaris under Canis lupus with the comment: "Probably ancestor of and conspecific with the domestic dog, familiaris. Canis familiaris has page priority over Canis lupus, but both were published simultaneously in Linnaeus (1758), and Canis lupus has been universally used for this species", which avoided classifying the wolf as the family dog. The dog is now listed among the many other Latin-named subspecies of Canis lupus as Canis lupus familiaris.
In 2003, the ICZN ruled in its Opinion 2027 that if wild animals and their domesticated derivatives are regarded as one species, then the scientific name of that species is the scientific name of the wild animal. In 2005, the third edition of Mammal Species of the World upheld Opinion 2027 with the name Lupus and the note: "Includes the domestic dog as a subspecies, with the dingo provisionally separate - artificial variants created by domestication and selective breeding". However, Canis familiaris is sometimes used due to an ongoing nomenclature debate because wild and domestic animals are separately recognizable entities and that the ICZN allowed users a choice as to which name they could use, and a number of internationally recognized researchers prefer to use Canis familiaris.
The origin of the domestic dog is not clear. The domestic dog is a member of genus Canis (canines) that forms part of the wolf-like canids, and is the most widely abundant carnivore. 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. The archaeological record shows the first undisputed dog remains buried beside humans 14,700 years ago, with disputed remains occurring 36,000 years ago. These dates imply that the earliest dogs arose in the time of human hunter-gatherers and not agriculturists. The dog was the first domesticated species.
Where the genetic divergence of dog and wolf took place remains controversial, with the most plausible proposals spanning Western Europe, Central Asia, and East Asia. This has been made more complicated by the most recent proposal that fits the available evidence, which is that an initial wolf population split into East and West Eurasian wolves, these were then domesticated independently before going extinct into two distinct dog populations between 14,000-6,400 years ago, and then the Western Eurasian dog population was partially and gradually replaced by East Asian dogs that were brought by humans at least 6,400 years ago.
- The term dog typically is applied both to the species (or subspecies) as a whole, and any adult male member of the same.
- An adult female is a bitch. In some countries, especially in North America, dog is used instead due to the vulgar connotation of bitch.
- An adult male capable of reproduction is a stud.
- An adult female capable of reproduction is a brood bitch, or brood mother.
- Immature males or females (that is, animals that are incapable of reproduction) are pups or puppies.
- A group of pups from the same gestation period is a litter.
- The father of a litter is a sire. It is possible for one litter to have multiple sires.
- The mother of a litter is a dam.
- A group of any three or more adults is a pack.
Domestic dogs have been selectively bred for millennia for various behaviors, sensory capabilities, and physical attributes. Modern dog breeds show more variation in size, appearance, and behavior than any other domestic animal. Dogs are predators and scavengers, and like many other predatory mammals, the dog has powerful muscles, fused wrist bones, a cardiovascular system that supports both sprinting and endurance, and teeth for catching and tearing.
Size and weight
Dogs are highly variable in height and weight. The smallest known adult dog was a Yorkshire Terrier, that stood only 6.3 cm (2.5 in) at the shoulder, 9.5 cm (3.7 in) in length along the head-and-body, and weighed only 113 grams (4.0 oz). The largest known dog was an English Mastiff which weighed 155.6 kg (343 lb) and was 250 cm (98 in) from the snout to the tail. The tallest dog is a Great Dane that stands 106.7 cm (42.0 in) at the shoulder.
The dog's senses include vision, hearing, sense of smell, sense of taste, touch and sensitivity to the earth's magnetic field. Another study suggested that dogs can see the earth's magnetic field.
- See further: Dog anatomy-senses
The coats of domestic dogs are of two varieties: "double" being common with dogs (as well as wolves) originating from colder climates, made up of a coarse guard hair and a soft down hair, or "single", with the topcoat only.
Domestic dogs often display the remnants of countershading, a common natural camouflage pattern. A countershaded animal will have dark coloring on its upper surfaces and light coloring below, which reduces its general visibility. Thus, many breeds will have an occasional "blaze", stripe, or "star" of white fur on their chest or underside.
There are many different shapes for dog tails: straight, straight up, sickle, curled, or cork-screw. As with many canids, one of the primary functions of a dog's tail is to communicate their emotional state, which can be important in getting along with others. In some hunting dogs, however, the tail is traditionally docked to avoid injuries. In some breeds, such as the Braque du Bourbonnais, puppies can be born with a short tail or no tail at all.