A professor is sent to live with a primitive African tribe. He spends years with them, teaching them reading, writing, math and science.
One day the wife of the tribe's chief gives birth to a white child. The tribe is shocked, and the chief pulls the professor aside and says, "Look here! You're the only white man we've ever seen and this woman gives birth to a white child. It doesn't take a genius to figure out what happened!"
The professor replied, "No, Chief. You're mistaken. What you have here is a natural occurrence, what we call an albino! Look at that field over there....