After reading your replies I can see that you believe that evolution should be able to explain why there are still monkeys if we evolved from them, when it needs to do nothing of the sort. Evolution doesn't say we evolved from monkeys, it says we have a common ancestor. Also, natural selection is not for getting rid of mutations. Natural Selection is the process by which something more adapted to its environment will survive to reproduce than something else, if a mutation allows them to survive better, it will be more likely to reproduce.