I suspect the reason is that most people [...] have a residue of feeling that Darwinian evolution isn't quite big enough to explain everything about life. All I can say as a biologist is that the feeling disappears progressively the more you read about and study what is known about life and evolution. I want to add one thing more. The more you understand the significance of evolution, the more you are pushed away from the agnostic position and towards atheism. Complex, statistically improbable things are by their nature more difficult to explain than simple, statistically probable things.
Richard DawkinsThere is economics in biology, nothing is free, everything has to be paid for, there are costs as well as benefits to everything in life, for example, there was never sufficient natural selection pressure to develop better eyes, individuals could earn other things like smiley smiles rather than waste energy & time on better eyes.
Richard Dawkins