Some argue that firm lines should be drawn in public policy and professional practice, against particular degrees of enhancement, like “species-altering interventions” (Annas, Andrews and Isasi, 2002) or “radical enhancements” (Agar 2013). The assumption here is that the moral problems raised by enhancement intensify as the enhanced move away from the human norm, and that a threshold can be identified beyond which prohibition would be merited. Since drawing the line at all enhancement uses of medical technologies would founder against too many contentious borderline and benign cases, this threshold is usually set at the boundary of our species identity, between the human and the post-human. As we have seen, this leaves many problematic enhancements in particular settings—like “gene doping” in sports—unaddressed, and it is still not clear what moral salience sheer taxonomy can have, apart from other ethical considerations—especially when one recalls the pernicious policies other human taxonomies have supported in the past. In practice, such an approach would face all the classic line-drawing problems, and the classic challenges of policing and enforcing prohibitions in a pluralistic and globalized society. Most importantly, however, if it is only those alterations that literally produce new biological species that are of concern the vast bulk of potentially problematic enhancement modifications would not fall within the jurisdiction of this approach. 