We went from wolves to chihuahua in just 40k years. Yeah selective breeding and all that, but it emphasizes that you can have very extreme changes in very brief periods of time. Imagine chihuahuas didn't exist today, and somebody said that within 40k years you could turn a wolf into one. It'd sound absurd!
Biology is quite arbitrary. For instance the dingo is basically just a wild dog, looks like a dog, can breed and create fertile offspring with dogs, yet is considered its own species.
So I prefer things that are more visceral in nature. There are lots of dogs that look a lot like wolves, but going from a wolf to a chihuahua is just kind of mind boggling in terms of the degree of change over such a small window of time. There's one extremely disappointed great great great ... grandfather wolf somewhere. 'Kids these days.'
