More than half a century has passed since the horrors of the Nazi racial extermination camps were revealed to a disbelieving world. Yet the battle of ethnic hate and violence remains one of the burning issues of our time. Billions of dollars are spent fighting it. Oprah devotes entire programs to it. Presidents consult civic and religious leaders; everyone seems to be wrestling with the problems of racial prejudice, yet solutions evade us. What does "race" really mean? Are there really multiple races of humans? Where did this concept originate?