In an idealised world the thousand white swans and 10 black swans will be mixed randomly, and you would be right. In the real world bird move in flocks, the pre

In an idealised world the thousand white swans and 10 black swans will be mixed randomly, and you would be right. In the real world bird move in flocks, the presence of one group of birds frightens off different birds. You may live in the hemisphere with only white swans and never as long as you live see a black one, but just over the hill there is a big population, it just lives in a place you haven't looked. In natural systems observations are biased. You reasoning is based on ideal assumptions.