One of my favorite examples of the step-by-step evolution of molecules has been the work coming out of Joe Thornton's lab on glucocorticoid receptors. It's marvelous stuff that nails down the changes, nucleotide by nucleotide.
It's also work that Michael Behe called "piddling", despite the fact that it directly addresses the claims of irreducible complexity. Have you ever noticed how the creationists will make grand demands (show me how a duck evolved from a crocodile!) and then reject every piece of fossil evidence you might show them because there are still "gaps"? This is the converse of that argument: when you've got a system where you can show each tiny molecular/genetic change, they dismiss that as trivial. You really can't win.
Well, Thornton has been working hard and coming up with more and more details, while Behe is still sitting there, eyes clamped shut and ears stoppered, insisting that IT CAN'T HAPPEN LALALALAALALALALAAAA. Behe threw together some dreck claiming that not only didn't Thornton's work demonstrate evolution, but it actually supported Intelligent Design creationism!
Boy, did he make a mistake.
Remember how when the creationists started playing games with his work, it roused Richard Lenski to slap down Conservapædia hard? We've got a similar situation here.
Read it. Really. It's a whole lesson in important principles in evolutionary theory all by itself. It exposes the ignorance of Behe through and through, and demolishes the premises of Behe's latest foolish book. And it made me feel soooo gooooood.