His research interests cover a broad range of international security issues, including information warfare, the causes and consequences of nuclear proliferation, the origins of wars and ethnic conflict, terrorism, and United States national security policy. He received his Ph.D. from the University of Chicago, and has been a Fellow at the Belfer Center for Science and International Affairs at the Kennedy School of Government at Harvard University and a consultant to the Rand Corporation. He is the author numerous books including Darwin and International Relations: On the Evolutionary Origins of War and Ethnic Conflict (Lexington: University Press of Kentucky, 2004) and American Empire: A Debate (New York: Routledge, 2007) with Christopher Layne.