Mbarka Mint Essatim was 23 when she discovered she was a slave. Her master's driver saw her doing heavy lifting one day and asked if she was paid. When Mbarka said 'no,' he told her the truth about the family she had always considered her own. I knew no one else and thought they were my family, she said of her masters, members of the light-skinned elite known as white Moors in the west African country of Mauritania. She neither looked like them nor lived like them. I did not sleep with them in the same house. I was afraid of them, they struck me ... raped me. I wanted to be like children my age, going to school and studying. I was alone. She tells the story coolly, sitting in a makeshift...