I saw a most interesting show on National Geographic channel the other day. They said that dogs have 'slippery' genes, hence the variety of sizes etc. Apparently they're the only animal with it. Also, they showed a group of people somewhere in Eastern Europe who are doing research on domestic dogs and wolves. They raised a group of domestics and a group of wolves from puppyhood. Then they tested them. For example, 2 pots were placed at a distance with a human standing between them. A dog (or wolf) was then placed ~ 8' from the pots + person. The person pointed to the pot with actual meat in it. The dog watched the person and went to the pot with the meat. The wolf did not. In a second test they tied a piece of meat to a rag in such a way that the dog (or wolf) could not get to it. The wolf continued to try, becoming very frustrated. The dog tried, then stopped and looked at the human for assistance. It was really fascinating. BTW, my dog thinks she's a wolf. Big time squirrel hunter!