A European missionary goes to an African tribe...

... and asks the tribeleader if he may stay with them. The leader agrees on one condition: No white child can be born.

However, 9 months later, a woman is discovered with a white child. The leader summons the missonary to explain himself. The missionary looks out the window and shows the leader a herd of sheep and says: " As you can see, all the sheep are white, yet one of them is black... "

In complete distress, the tribeleader exclaims: " Allright, I won't say anything about your child, as long as you don't say anything about the sheep!"