@ Draug - the reasons you don't find mistakes in the fossil record is because evolution isn't about making big mistakes, big mistakes are incredibly rare, and don't survive, and don't proliferate through the gene pool (and fossilization is an incredibly rare phenomenon as well. The odds of these two unlikely events overlapping and a non-functional freak of nature fossilizing is very slim indeed, something like 1 in 100000 multiplied by 1 in a million). Furthermore, evolution is not really about trial and error, it's about gradual improvement. And there are plenty of things in the fossil record that look like birds but can't quite fly, (but do in fact glide, or flap or jump, or something). They don't look like mistakes though, because they were still functional, just in a way that couldn't fly as well as a bird, but it could still make a life, fill a niche in the ecosystem.