I heard a story on Discovery Channel or something like that where they claimed dogs came to be man's best friend because a lot of dog species found it easier to just follow humans around and eat their scraps than it was to hunt on their own. Over time they began to work well together.
yeah there are alot of canine species...wolves were just one so no most dogs did not evolve from wolves.
The smaller variations were bred to be that way so you can say they artificially evolved much like the plants we grow to be bigger.
My theory is that many dogs were domesticated b/c they were prone to domestication. Likely they were in areas that humans migrated to much like horses and cows were. Without those millions of years of co-evolution and adaptation to humanity's crude attempts at domestication these animals had no genetic fear of humans and were prone to domestication. Compare a horse and a zebra if you will to see the difference. There is no way in hell a zebra would allow you to ride it. This may apply to many dogs as well.
The Domesticated Dog is the same species as the wolf. It's just a different breed. Thousands of years of selective breeding has given us the Dog species we have today. (Actually, you might want to double check my facts, but I believe I'm right)