" If the tillers of the soil from the north were Caucasians," I said, "then the mark of Cain is this." I pointed to my own fair or maggot-colored face.
..."The mark was given to Cain as a warning to others: 'Leave this man alone. This is a dangerous man, one who enacts a sevenfold vengeance.' Certainly a lot of people all over the world have learned that it doesn't pay to mess with people with white faces. "

― Daniel Quinn , Ishmael (Ishmael, #1)