How Are New Dog Breeds Created?

The Westminster Dog Show just allowed seven new breeds to join the competition, but how are new breeds created?

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Humans May Have Domesticated Dogs Tens of Thousands of Years Earlier Than Thought (Smithsonian)
"Dogs are so in tune with humans now that they can tell if their owners are happy or angry. That close relationship that has existed since before they helped early humans take down mammoths. But the exactly how long canines have provided companionship just got a revision."

The Incredible Explosion of Dog Breeds (Live Science)
"From a teacup-size Chihuahua to a Great Dane, there is an incredible amount of variety among dog breeds. But all breeds belong to a single species, so scientists have studied the breeds to better understand the workings of evolution, and how such great variation could have arisen within one group."