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Dogs have been
selectively bred for thousands of years. Initially the selections would have
centred on
domestication and useful qualities such as
hunting
ability. Later, dogs were also selected to give attractive and distinctive forms
resulting in a vast variety of types. The point at which a new variety becomes a
breed can be
difficult to decide. National
kennel
clubs often differ in their recognition of breeds and rare breeds might not
be recognised outside their home country. Usually, only dogs recognized by a
kennel club are eligible to compete in the club's
dog shows
and dog
sports, although many dog sports allow any healthy dog to compete regardless
of the breed.
Many traditional dog breeds recognised by the main registries are said to be
"purebred".
Only individuals whose parentage consists only of other purebred examples of the
breed are regarded as part of that breed. This concept has caused controversy
both because of the difficulty of regulation and because of the possible genetic
consequences of a limited population. Recent work has been done to genetically
classify the various breeds, with some surprising results regarding the
estimated age and interrelations of the breeds.
Generally, before a type of dog is recognized as a breed, it must be shown
that mating a pair of that type always produces dogs that have the same
characteristics as the parents, usually both in appearance and in behavior. This
is known as breeding true. There are many issues concerning what is
considered breeding true. For example,
Flat-Coated Retrievers must always be black; however, yellow coats occur
occasionally in some litters. Kennel clubs do not recognize the yellow dogs as
legitimate members of the breed; some breeders will
euthanize the puppies rather than risk having the dog grow up, breed, and
produce more of the undesired yellow color; more often, today, such dogs are
neutered and placed in homes as
pets. As another
example, a breeding pair of
Belgian Shepherds of the
Groenendael variety can produce puppies of the
Tervueren (brown) variety; the
AKC considers the varieties to be different breeds and, therefore, the brown
puppies are invalid and undesirable dogs, whereas the
CKC considers them
simply to be different varieties.
See
selective breeding for a detailed discussion on open versus closed studbooks
and some of the issues concerning purebreds.