First off, thank you so much for putting together a forum such as this. I've never been to college or even taken a biology class, but am absolutely fascinated by science and devour science media in my spare time (I'm a self-taught physics geek). Recently I've found myself trying to explain the process of evolution to my evangelical girlfriend and her father, but in the process have realized there are quite a few things I'm not entirely sure of myself. Understand that I am firmly in support of the Scientific Method vs any religious dogma, as one is based on required falsifiabilty and the other infalability. And I've already burned through the common misconceptions creationists have about evolution that are most often based on ignorance to begin with. But one area that I stumbled upon that I feel I may need to explain someday is something that I'm not entirely sure about myself and that's the Cambrian Explosion.
Where do Biologists (or maybe Paleontologists) stand on this issue? There seem to be a wide variety of theories. From what I gather the fossil record shows an abrupt spike in the rise of very diverse life roughly 500 million years ago and logic would lead me to believe that this can be explained by the a severe change in the Earth's environment that created a rich habitat for life to propogate. From what I've been reading, Creationists use this as some kind of evidence of instantaneous divine creation, regardless of the "age" issue.