This is a very simple argument, so don't tear me a new one if I miss something. The rules of Cause and Effect demand that EVERYTHING that happens was caused by something acting before it. No scientist I've heard of can explain what caused the Big Bang. They believe the Big Bang happened, but they don't know what happened before it to cause it. My answer is that God caused the Big Bang, then sat back and tweaked the Universe as he saw fit, until it was time for us. (Remember, time is irrelevant to God) Like I said, it's a very simple argument, but this way a Christian can believe in both Creation and Evolution.