Picture your heart. What would happen if there was something wrong with it? If it wasn't fatal, you'd certainly be at a disadvantage in a survival situation. The heart is vital to the survival of every creature in which it exists.
Now imagine a half-evolved heart. Would it give a survival advantage? Of course not! It would be fatal. The heart, therefore, could not evolve, because every possible stage between us and our mythical heartless ancestors would die as soon as they were born.
And that's just taking the heart as a lone example. Your lungs, your brain, your stomach, your intestines, all the things that connect these things to other things, none of these things could possibly come about over generations. Natural selection, therefore, kills Evolution before it gets started, simply because transitional forms would be naturally selected against.