Etymology and related terminology

The English word dog can be traced back to the Old English docga, a "powerful breed of canine".[5] The term may derive from Proto-Germanic *dukkôn, represented in Old English finger-docce ("finger-muscle").[6] Due to the linguistically archaic structure of the word, the term dog may ultimately derive from the earliest layer of Proto-Indo-European vocabulary, reflecting the role of the dog as the earliest domesticated animal.

 The English word hound is cognate to other Germanic terms, including German Hund, Dutch hond, common Scandinavian hund, Icelandic hundur which, though referring to a specific breed group in English, means "dog" in general in the other Germanic languages. Hound itself is derived from the Proto-Indo-European *kwon-, which is also the direct root of the Greek κυων (kuôn) and the indirect root of the Latin canis through the variant form *kani- In breeding circles, a male canine is referred to as a dog, while a female canine is called a bitch. The father of a litter is called the sire, and the mother of a litter is called the dam. Offspring are generally called pups or puppies until they are about a year old. A group of offspring is a litter. The process of birth is whelping. Many terms are used for dogs that are not purebred.[9]

Taxonomy

The English word dog, in common usage, refers to the domestic pet dog, Canis lupus familiaris. The species was originally classified as Canis familiaris and Canis familiarus domesticus by Linnaeus in 1758.  In 1993, dogs were reclassified as a subspecies of the gray wolf, Canis lupus, by the Smithsonian Institution and the American Society of Mammalogists. "Dog" is sometimes used to refer collectively to any mammal belonging to the family Canidae (as in "the dog family"), such as wolves, foxes, and coyotes. Some members of the family have "dog" in their common names, such as the Raccoon Dog and the African Wild Dog. A few animals have "dog" in their common names but are not canids, such as the prairie dog and the dog fish.

 Origin and evolution

 Main article: Origin of the domestic dog

Based on DNA evidence, the wolf ancestors of modern dogs diverged from other wolves about 100,000 years ago, and dogs were domesticated from those wolf ancestors about 15,000 years ago. This date would make dogs the first species to be domesticated by humans. Evidence suggests that dogs were first domesticated in East Asia, and some of the peoples who entered North America took dogs with them from Asia. As humans migrated around the planet, a variety of dog forms migrated with them. The agricultural revolution and subsequent urban revolution led to an increase in the dog population and a demand for specialization. These circumstances would provide the opportunity for selective breeding to create specialized working dogs and pets.

 Ancestry and history of domestication

Main article: Origin of the domestic dog

 This ancient mosaic, likely Roman, shows a large dog with a collar hunting a lion. In Jan van Eyck's famous Arnolfini Portrait (1434). Care was taken to include the couple's little pet dog.Molecular systematics indicate that the domestic dog (Canis lupus familiaris) descends from one or more populations of wild wolves (Canis lupus). As reflected in the nomenclature, dogs are descended from the wolf and are able to interbreed with wolves. The relationship between human and canine has deep roots. Converging archaeological and genetic evidence indicate a time of domestication in the late Upper Paleolithic close to the Pleistocene/Holocene boundary, between 17,000 and 14,000 years ago. Fossil bone morphologies and genetic analysis of current and ancient dog and wolf populations have not yet been able to conclusively determine whether all dogs descend from a single domestication event, or whether dogs were domesticated independently in more than one location. Domesticated dogs may have interbred with local populations of wild wolves on several occasions (a process known in genetics as introgression).

The earliest dog fossils, two crania from Russia and a mandible from Germany, date from 13,000 to 17,000 years ago. Their likely ancestor is the large northern Holarctic wolf, Canis lupus lupus. Remains of smaller dogs from Mesolithic (Natufian) cave deposits in the Middle East, dated to around 12,000 years ago, have been interpreted as descendants of a lighter Southwest Asian wolf, Canis lupus Arabs. Rock art and skeletal remains indicate that by 14,000 years ago, dogs were present from North Africa across Eurasia to North America. Dog burials at the Mesolithic cemetery of Svaerdborg in Denmark suggest that in ancient Europe dogs were valued companions.

Dogs on the Coat of Arms of the Canary Islands, which in ancient times had a dense population of an endemic breed of large and fierce dogs. Genetic analyses have so far yielded divergent results. Vilà, Savolainen, and colleagues (1997) concluded that the ancestors of dogs split off from other wolves between 75,000 and 135,000 years ago, while a subsequent analysis by Savolainen et al. (2002) indicated a "common origin from a single gene pool for all dog populations" between 40,000 and 15,000 years ago in East Asia. Verginelli et al. (2005),[16] however, suggest both sets of dates must be reevaluated in light of recent findings showing that poorly calibrated molecular clocks have systematically overestimated the age of geologically recent events. On balance, and in agreement with the archaeological evidence, 15,000 years ago is the most likely time for the wolf-dog divergence.

The Soviets have attempted to domesticate the fox, mentioned in the article Tame Silver Fox, and were able to do so in just nine generations, or less than a human lifetime. This also resulted in other changes, including color, which became black, white, or black and white. They also developed year-round breeding ability, curled-up tails, and droopy ears. The rapidity of this change has suggested to researchers a scenario of the origin of the domestic dog. Primitive people lived on the edge of survival which involved occasional food shortages, and would not have taken wolf pups and made pets of them. However, wolves would raid garbage dumps near human habitations. Wolves have a flight distance which they keep between themselves and a threatening creature. When a dump was approached by humans, some wolves would run a greater distance from the dump than others. Those that ran the shortest distance would return first, and obtain the greatest amount of food.

This set up a selective breeding situation that resulted in a strain of wolves having shorter and shorter flight distances, until they were eventually comfortable near humans, having domesticated themselves, so to speak. At that point, they were tolerated by humans, so long as they were also useful, in such ways as catching rats or driving away other predators. In time, other uses, such as hunting, were found for them. The Farm Fox

Experiment Evolution of Dogs. Development of dog breeds.

Main article: Dog breeds

Dogs have been bred into a variety of shapes, colors and sizes. Variation can be wide even within a breed, as with these Cavalier King Charles Spaniels.There are numerous dog breeds, with over 800 being recognized by various kennel clubs worldwide. Many dogs, especially outside the United States of America and Western Europe, belong to no recognized breed. A few basic breed types have evolved gradually during the domesticated dog's relationship with humans over the last 10,000 or more years, but all modern breeds are of relatively recent derivation. Many of these are the product of a deliberate process of artificial selection. Because of this, some breeds are highly specialized, and there is extraordinary morphological diversity across different breeds. Despite these differences, dogs are able to distinguish dogs from other kinds of animal.

The definition of a dog breed is a matter of some controversy. Depending on the size of the original founding population, closed gene pool breeds can have problems with inbreeding, specifically due to the founder effect. Dog breeders are increasingly aware of the importance of population genetics and of maintaining diverse gene pools. Health testing and new DNA tests can help avoid problems, by providing a replacement for natural selection. Without selection, inbreeding and closed gene pools can increase the risk of severe health or behavioral problems. Someorganizations define a breed more loosely, such that an individual may be considered of one breed as long as 75% of its parentage is of that breed. These considerations affect both pets and the show dogs entered in dog shows. Even prize-winning purebred dogs sometimes possess crippling genetic defects due to founder effect or inbreeding.[18] These problems are not limited to purebred dogs and can affect cross-breed populations.[19] The behavior and appearance of a dog of a particular breed can be predicted to a degree, while mixed-breed dogs show a broader range of innovative appearance and behavior.

This puppy is a mix of many breeds.Mixed-breed dogs or Mongrels (also called "mutts") are dogs that do not belong to specific breeds, being mixtures more than two in variant percentages. Mixed breed dogs and purebred dogs are both suitable as companions, pets, working dogs, or competitors in dog sports. Sometimes different breed dogs are deliberately bred, to create cross-breeds such as the Cockapoo, a mixture of Cocker Spaniel and Miniature Poodle. Such deliberate crosses may display some degree of hybrid vigor and other desirable traits, but may or may not inherit any of the desired traits of their parents, such as temperament or a particular color or coat. Without genetic testing of the parents, the crosses can end up inheriting genetic defects that occur in both parental breeds.

A breed is a group of animals that possesses a set of inherited characteristics that distinguishes it from other animals within the same species. Deliberately crossing two or more breeds is also a manner of establishing new breeds, but it is only a breed when offspring will reliably demonstrate that particular set of characteristics and qualities. The Bulldog is well known for its short muzzle and saggy skin on its face

Breed popularity

Breed popularity varies widely over time[20] and in different parts of the world and different segments of the population. Counting by American Kennel Club (AKC) registration (not by licensing registration or by United Kennel Club (UKC) registration, which could present different statistics), the Labrador Retriever has been the United States's most commonly registered breed of dog since 1991.[21] However, even within parts of the United States, popularity varies; for example, in 2005 the most-registered breed in New York City was the Poodle while the Yorkshire Terrier was the second-most-registered breed in Houston.[22] However, animal shelters in many parts of the United States report that the most-commonly available dog for adoption is the American Pit Bull Terrier or pit bull-type mixes, making up as much as 20% of dogs available for adoption, none of which would be registered with the AKC.[23] Two decades ago, in 1983, the AKC's top two registered breeds were the American Cocker Spaniel and the Poodle.[24]

In the United Kingdom, The Kennel Club reports that the most-registered breed from at least 1999 to 2005 was the Labrador Retriever. It rounds out the top three for 1999 to 2005 with the German Shepherd Dog, also popular in the US, and the English Cocker Spaniel[25], which is no longer in the top ten in the US. In the UK, a national dog adoption and rescue service indicates that the most common breed appearing in shelters is the Greyhound followed by the Staffordshire Bull Terrier.

Differences from wolves Physical characteristics

Compared to equally sized wolves, dogs tend to have 20% smaller skulls and 10% smaller brains, as well as proportionately smaller teeth than other canid species.[3] Dogs require fewer calories to function than wolves. Their diet of human refuse in antiquity made the large brains and jaw muscles needed for hunting unnecessary. It is thought by certain experts that the dog's limp ears are a result of atrophy of the jaw muscles. The skin of domestic dogs tends to be thicker than that of wolves, with some Inuit tribes favouring the former for use as clothing due to its greater resistance to wear and tear in harsh weather. Unlike wolves, but like coyotes, domestic dogs have sweat glands on their paw pads. The paws of a dog are half the size of those of a wolf, and their tails tend to curl upwards, another trait not found in wolves.

 

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