Historians estimate that between 650 AD and the 1960s, 10 to 18 million people were enslaved by Arab slave traders. They were taken from Europe, Asia and Africa across the Red Sea, Indian Ocean, and Sahara desert. Male slaves were often employed as servants, soldiers, or workers by their owners. Many male slaves were castrated. It is estimated that as many as 6 out of every 10 boys bled to death during the process. But the high price of Eunuchs made it worthwhile. According to Ronald Segal, author of "Islam’s Black Slaves: The Other Black Diaspora" (2002), "The calipha in Baghdad at the beginning of the 10th Century had 7,000 black eunuchs and 4,000 white eunuchs in his palace”. Women and children taken as slaves were mainly used as servants and concubines. While the later Atlantic slave trade concentrated on men for labor, the Arab slave trade started with men and boys, but shifted over time to concentrate more on woman and young girls for sexual purposes. By the 1900s, Arab slave traders had taken between 10 and 20 million slaves out of Africa.