From the dawn of Man's Age to the present time,
we have forged a relationship with the dog
Being an intelligent species Man began to selectively breed the wolf to exhibit characteristics that man wanted. They bred for more "tame" animals that would transfer their wild pack instincts to including the family of man as his pack and relinquishing his leadership to man.
Wolves were bred for specific purposes such as guarding hearth and home, herding livestock, retrieving kills from the hunt, and more. Somewhere along the line man realized that the wolf was, in many ways, far more cunning than he was. In order to maintain the leadership role, he would have to breed for less intelligence and basically "lock his dogs in puppy hood".
As evidence to this, Adult Dogs play, Adult Wolves hunt but do not play. In a wolf pack it is only the puppies that play.
Over the generations, man has continued the selective breeding of dogs for various types, as a result we have the wide variety of sizes and breeds of dogs known today.
Here the world's tallest dog meets the world's smallest dog