Based on results of molecular phylogenetic analyses and archaeological evidences, most researchers believe that the dog is descended from the wolf and that east Asia was the central place for the early events of domestication around 15,000-20,000BP. Many different theories of domestication have been proposed in respect of the evolutionary mechanism, and each theory can explain a particular aspect of the process which has different evolutionary backgrounds by its stage and phase. The dog is established in modern society as a companion animal. It has physiological and psychological benefits to human, which include facilitating therapy, reducing stress, and socialization. In addition to that, the dog has positive effects on child development and elderly people.