Very interesting question. You know when God created this earth, he never told anyone what or how he is going to do anything, because he is a mysterious God. Just like when he created the animals, he created some to fly, others to crawl, others to swim and paddle, do we know why he did that? No i don't think there is anyone who can answer that question but God himself. As the bible tells us, his thoughts are not our tgoughs he alone knows why and how. We can never challenge in God in anyway. Maybe if we can think just as human beings, we would say that he created some black and others white so that we would see how powerful he is and that he can do anything so that we know he is God. Even Adam and Eve were different it all started from there