Aping Ethics: Behavioral Homologies and Nonhuman Rights Fiery Cushman Introduction “He who understands the baboon,” penned Charles Darwin, “will do more towards metaphysics than Locke ” (Darwin and Barrett 1987). Darwin’s wry assessment appears in a private journal from 1838, and it reveals much more than the young biologist’s distaste for philosophical speculation. His success as a theoretician derived from decades of painstaking observation and empirical study, and it was these methods in which he invested full faith. Among Darwin’s greatest insights was that scientific study applies as much to human affairs as to the natural world—in short, that philosophers might benefit from a little biology. Today, the behavioral sciences provide perspective to philosophers that is just as important and infinitely more nuanced. At one of the more salient junctions of their disciplines, philosophers and biologists are taking more seriously the question of our obligations to non-human beings. It is rapidly becoming an unavoidable conclusion that animals share with humans not only common ancestors, but a common suite of behaviors and mental experiences. This is especially true of humans’ closest relatives, primates such as the chimpanzee and bonobo. Indeed, behavioral research has unmasked beneath simian faces perhaps the most human quality of all: a moral faculty. It goes without saying that there is no clear consensus on whether animals meet the criteria for moral worth—quite to the contrary, there is substantial disagreement over what the criteria ought to be. This conflict has deep historical roots. Jeremy Bentham, the father of utilitarian philosophy, argues that the key issue concerning animal welfare is not “Can the reason, nor Can they talk, but Can they suffer?” (Bentham, Burns et al. 1996) Bentham’s mantel is worn today by Peter Singer, who advocates for the rights of animals on precisely these grounds, but his approach is by no means universally accepted. Immanuel Kant, a representative of the deontological tradition in philosophy, disposes of the matter by declaring that “Animals are not self-conscious and are there merely as a means to an end” (Kant 1999). Kant’s position is apparently that a being