Best line I ever heard: "When God made all the animals, he didn't need to make a Dog because he already had one." My wife, who is Cherokee, believes that every animal has an origin, but as far as the dog, it goes like this:

When the Creator decided to bring the earth into existence, He spread out a great tapestry and placed all living things upon it. As if to establish the hierarchy of living beings, He took His finger and drew a line down the middle of the canvas. A crack began to form, and all humans moved to one side of the crack and all animals moved to the other side. The crack grew wider and wider, on its way to become a chasm. At the moment right before the chasm became too wide to cross, Dog jumped over and stood by Man.

Hard to disagree with that :)