The role of biology in human conflict has been a perennial concern for those who reflect on the causes and nature of war. Now, revolutionary advances in the bio-medical sciences are reorienting how we think about these issues, as well as providing new tools to deal with them. The implications for security studies will undoubtedly be widespread. However, the sheer quantity and scope of novel biological research confronts us with the challenge of understanding where its true promises lie. From a theoretical perspective we need to ask whether new research fundamentally changes important paradigms in the field. From a practical perspective, finite resources force us to make bets on which research is likely to be most useful to pursue. Thus it is worth taking a bird’s eye view to survey and appraise the promises and limits of biological research as it relates to security issues across the board.