A professor travels to Africa to live with a primitive tribe and spends years with them, teaching them all about the wonders of science and mathematics.
He makes friends with the tribe's chief and his wife and they all live happily for some time.
One day the chief's wife gives birth to a white child.
The word spreads and the entire tribe is in shock.
The chief pulls the professor aside and says, "Look, you are the only white man we've ever seen around here, and my wife gave 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 we have here is a natural occurrence what we in the civilized world call an albino!
Look at that field over there.
All the sheep are white except for one black one.
Nature does this on occasion."
The chief was silent for a moment, then said, "Tell you what.
You don't say anything more about that sheep and I won't say anything more about the white kid."