I'd say neither. How can we be considered mistakes? Think about the way our body works. It's amazing how everything cooperates so seamlessly. It's to great to be a coincidence. Something like the human body had to be intentional.
God can't be considered a mistake of man either. Whether there actually is a God or Great Beyond is irrelevant. If the foundation of an idea could hold people responsible for their actions to a "Judge" whose judgment and sight they can't escape then it creates a better world. Although radicals, such as terrorists, exist, the fundamental ideas that a God stands for could never be considered a mistake.