Not a guessing game but selection, selection is what nature does naturally and we have to learn to do by eye. Its what lies behind all good live stock breeding..
Very true. One thing to always keep in mind though is that species evolve naturally at a very slow pace. We as breeders of dogs can make it or break in one breeding. The good thing though is that we can also "fix" it in a rather short period of time if we at least try to.