Most black cats have a white spot because of their middle-ages persecution!
Most black cat owners discover that they have one or more white spots on their body. The reason for this has a lot to do with the Middle Age persecution that cats suffered. When they became associated with dark magic and sorcery, the Church burned black cats alive because they were considered to come from the devils.
As a result of the persecution, the number of black cats diminished, but their relatives that had white spots increased all the time. The church had mimicked natural selection!