Argument #3: Mutations

[Tonus]

It's quite true that mutations that seem to confer no immediate benefit (or might even be deleterious) can be passed down from generation to generation if they do not prevent the population from breeding. In time a 'bad' mutation may prove useful if there is a change in the organism's surroundings. A fish that develops the ability to breath air may be at a disadvantage at first (having to surface to breathe and at risk of drowning), but it may be the only survivor when the lake dries up or when larger, lake-bound predators appear and the land becomes the safer option.

The fact that so many mutations are either useless or harmful would not speak to an intelligent designer, but fits within the framework of evolutionary theory and the evidence that has been found so far. A great many of the creatures which have existed have long since gone extinct, while some have continued to breed and survive for millions of years, sometimes with seemingly few changes (sharks, for example). This apparent randomness speaks more towards a natural process and not an "intelligent" one.