what you don't seem to understand is that evolution does not simply occur in a vacuum. evolution occurs due to natural selection overcoming a problem. in order to breed something you have to give it the best environment. with no problems to overcome, there is nothing for a new species to prove its better at, thus being selected over a proven variety.
lets take homosapiens. we were better hunters than are predecessors, thus they died out while we populated the globe. why? because food became more scarce as the climate changed. our predecessors were geared to a wetter, warmer environment, where we were more adjustable.
if a fruit fly shows up that is faster than the others, but is not close enough to get to the food when there are thousands of others closer, it will not have an advantage in a closed environment. in an open environment it would. therefore, breeding them does not encourage evolution, but rather discourages it.
evolution only occurs when a species is no long comfortable in its environment.
