Missionary in the jungle

A missionary lives with a tribe in the jungle, when one day the Chief of the tribe approaches him:

"You are the only white man around here, and now my daughter gave birth to a white child! Explain yourself, or prepare to die!"

The missionary hesitates for a moment, then replies:

"The nature is full of wonders. Look at those sheep over there. They are all white, except for one single lamb which is black."

The Chief: "... If you keep quiet, then I will too.”