Novelist Lisa Alther suspects that her family concealed its Melungeon heritage back when multiracial ancestry was frowned upon. While researching her memoir, Kinfolks: Falling off the Family Tree, she was able to confirm some facts about the bogeymen of her youth.
While growing up, she heard from a baby-sitter that Melungeons sported six fingers on each hand, all the better to "grab mean little children and carry them off to their caves in the cliffs outside of town."
This mythology was not entirely outlandish. As an adult, Alther's search led to Brent Kennedy, a respected Melungeon scholar and newfound cousin, in that they share the same grandmother's grandmother. He showed her the scars where his extra thumb on each hand had been removed. [Link]