Karl Jacoby is a professor of history at Brown University. He received his BA from Brown University and his PhD in American history from Yale University. His research centers on the roles human and nonhuman actors have played in shaping the past. Jacoby is particularly interested in understanding how relations of power within human society are reinforced, complicated, and, at times, effaced through interactions with the natural world. He has found the history of U.S. expansion an especially fertile area to explore such issues. Jacoby is the author of Crimes against Nature: Squatters, Poachers, Thieves, and the Hidden History of American Conservation (University of California Press, 2003) and Shadows at Dawn: An Apache Massacre and the Violence of History (Penguin, 2009). Jacoby shared his research from Shadows at Dawn with the Choices Program, which was influential in the creation of Westward Expansion: A New History.