Almost every radical evolutionary conviction circulating today has as its source some thinker in the years after Darwin but before acceptance of his theory as dogma. No one was more sensitive to the weaknesses of Darwinian theory than Darwin himself. As an example of trouble, Darwin volunteered the astounding multifaceted sophistication of the human eye. The eye to this day gives me a cold shudder. The difficulty Gray had was imagining how any portion of an unfinished eye, a retina without lens or vice versa, would be useful to its possessor.
Breakthroughs have to work the first time.
Even clever humans can't design in such a consistently demanding manner. Therefore nature appears superhuman in its ability to create. This is what makes coral reefs and armadillos out of bacteria, Darwin said-accumulated microchange. Darwin asks that we extend the logic of microchange to cover the grand scale of Earth and Time. The argument that natural selection can be extended to explain everything in life is a logical argument.