The question of the “frontiers of humanity” is at the heart of the social sciences project. It is possible to distinguish two ways of addressing the issue. The first is normative: the aim is to draw a line between what is “peculiar to humans” and what is not. The second way of considering the “frontiers of humanity” is descriptive: it is a form of reflection on the way in which any being can be humanized or dehumanized. From this point of view, humanity appears to be the result of processes that make it either appear or disappear. For twenty years now, the fields of biomedicine and of disability are both characterized by a particularly complex work concerning the “frontiers of humanity” understood in the second meaning: this issue tries to give a comprehensive overview of it. Beyond these two fields, sociology of the “frontiers of humanity” is an invitation to investigate various settings, maybe more ordinary, in which membership in a common humanity is at stake.