What stops the mirco changes from building up till they are macro?
Just trillions and trillions of iterations, which there isn't enough time in stable earth history to roll the dice that many times. That line of reasoning doesn't do it for me. It's similar to the infinte number of monkeys argument. Yes, theoretically they could write the works of Shakespeare if you give them enough time, but there isn't enough time to prove that experiment. I'm neither a mathemetician nor a biologist, just a non-believer in evolution. To me, it's a religion, and all religions require some degree of faith. Evolution (as an explanation for the entirety of sentient life) requires way more faith than I have. But I do not disparage it if it happens to be your belief.