Bioethical Assessment of Research with Humanoid or Humanized Biological Entities with Uncertain Moral Status

A number of studies have been conducted in recent years with humanoid or humanized biological entities such as hybrids or mixtures of species that involve a human contribution to the resulting individual. These include embryos whose genetic makeup is exclusively human but which do not come from the fertilization of gametes, and embryoid models obtained from stem cells, all of them with an uncertain moral status. Both conceptual and empirical limitations make it difficult to classify such entities within the pre-established biological categories, resulting in uncertainty as to the moral licitness of generating such entities and using them in experimentation. In the question of chimera research, the state of science currently permits a very low human contribution to the animal individual, so there are no doubts about the biological nature and moral status of the chimeras that can now be generated. However, the possibility of further refinement of the technique requires us to consider what limits to set in this regard. Given the inability to establish clear boundaries to systematize the degree of differences that should distinguish zygotes and embryos obtained by fertilization from those obtained by cloning, parthenogenesis or induced cellular dedifferentiation, the principle of bioethical prudence should be applied to current research with a view to preventing them from threatening human lives which, even in a very genetically imperfect state, should continue to be regarded as such.