In this episode of Talk Nerdy, Cara is joined by author, broadcaster, and scientist Dr. Adam Rutherford to talk about his newest book, "How to Argue With a Racist: What Our Genes Do (and Don't) Say About Human Difference." They discuss the racist history of academic science and psychology, what ancestry DNA tests can and can't tell you about your past, and of course, how to argue with a racist. Follow Adam: @AdamRutherford.