I believe we are at present observing just such a mutation. In numbers that not even Science could have predicted, an entire generation of humans has been born with an inexplicable mutation in their breathing apparatus. For reasons that Nature will no doubt explain to us later, teenagers have evolved to breathe through their butt cracks. Unfortunately, the oppressive bounds of what the rest of haughtily refer to as good taste forced them into near suffocation for years. But today, though many continue to suffer, the majority, perhaps inspired by the mythical mutant pride of Charles Xavier's X-Men, have boldly lowered their pants and are breathing freely.
Now, before you make what seems to be the natural jump of using this undeniable and easily observed mutation as proof that there is no God, consider for a moment that no belief system that relies on proving another belief system wrong can possibly be right. A teenager walking around with his/her pants halfway down the butt-crack is merely a piece of a larger puzzle, a missing link, if you will, in the unfolding tapestry of human evolution.
What's next? Only several billion more years of careful observations will tell.