A dog may be man's best friend. But man is not always a dog's. Over the centuries selective breeding has pulled at the canine body shape to produce what is often a grotesque distortion of the underlying wolf. Indeed, some of these distortions are, when found in people, regarded as pathologies. Dog breeding does, though, offer a chance to those who would like to understand how body shape is controlled. The ancestry of pedigree pooches is well recorded, their generation time is short and their litter size reasonably large, so there is plenty of material to work with. Moreover, breeds are, by definition, inbred, and this simplifies genetic analysis. Those such as Elaine Ostrander, of America's National Human Genome Research Institute, who wish to identify the genetic basis of the features of particular pedigrees thus have an ideal experimental animal.
According to the text, what are the reasons of human producing pooches?