A white scientist is studying an African tribe.

One day, the tribe leaders wife has a white son.

The tribe leader approaches the scientist soon after.
“Well, we both know what happened here. No one else could have done it. You slept with my wife, I have to kill you.” The tribe leader says.

The scientist’s brow furrows as he is deep in thought.
“No no no sir there’s been a terrible misunderstanding!” The scientist exclaims. “Look out at the pasture.” He points his index finger to the fields, where a flock of sheep are grazing.
“Yes, what is the matter? It’s just sheep.” The tribe leader asks.
“Do you see that sheep? It’s black, while the rest of the sheep are white. The same can be said about your son, It simply happens sometimes in nature.”

The tribe leader grasps the scientists shoulders and stares him down intensely.
“I won’t say anything about my son if you don’t say anything about that sheep”