It didn't stop. How and why didn't it stop? It never started. Check out "The Mathematical Impossibility of Evolution" at http://www.icr.org/article/mathematical-impossibility-evolution/. From the site: "All this means that the chance that any kind of a 200-component integrated functioning organism could be developed by mutation and natural selection just once, anywhere in the world, in all the assumed expanse of geologic time, is less than one chance out of a billion trillion. What possible conclusion, therefore, can we derive from such considerations as this except that evolution by mutation and natural selection is mathematically and logically indefensible!"