Good question. My train of thought has always been that there has to be two snow flakes exactly alike because God makes people and they say everybody has a twin somewhere in the world, especially people born identical twins. I wonder if they ever realize one of them was a mistake. But I degress. Now there are currently a little over 6 billion people alive on this planet and there are duplicates. There are gazillions of snow flakes every year. Some of them even walk around being offended all the time. So if God can't make 6 billion widgits without duplicates, how can Mother Nature make gazillions without duplicates. @Xelda and @GrammaJan will tell us it's because women never take a day of rest. Hmmm, maybe they're on to something there.