Dogs belong to Chordata, Vertebrate, Mammalia, Orthoptera, Carnivora, Schipoda and Canidae. Chinese is also called "dog", and dogs are distributed all over the world. Dogs, horses, cows, sheep, pigs and chickens are also called the traditional "six animals". Some scientists believe that dogs were domesticated by early humans from the gray wolf, and the domestication time was from 40,000 years ago to 1.5 million years ago. Known as "the most loyal friend of mankind", it is the pet with the highest reproductive rate, and its life span is about 12~ 18? [ 1]。 In China culture, dogs belong to one of the 12 Zodiacs, ranking 1 1 among the 12 Zodiacs.