  In the first journal article focusing on the ethics of chimeras, Jason Scott Robert and Françoise Baylis (2003) puzzle over the negative reaction exhibited by the public to human/non-human chimeras. Some people think that the public’s reaction is explained by a widely held belief in fixed and well-defined boundaries between species, or at least between the human species and non-human species, but in fact “no extant species concept justifies the erection of the fixed boundaries between human beings and nonhumans that are required to make breaching those boundaries morally problematic” (ibid., 6). Others think that what people find objectionable is that crossing species boundaries constitutes playing God, but many people do not believe in God and others believe that God not only licenses, but enjoins the kind of creative research involved in chimeras. Others think that people react to the prospect of chimeras with repugnance, but such reactions are not themselves sufficient grounds for concluding that an activity is immoral. Nor do people’s beliefs in its being taboo to blur sharp and significant conceptual boundaries explain their negative reaction, because the conceptual boundary between humans and non-humans is not sharp.