Bailey characterizes our argument in the exchange with Neaves and Magill as “convoluted.” At one point he even calls it “desperate.” But one would be hard put to decipher from Bailey’s account of that exchange what the basic issue was. In various places we have made explicit what is generally assumed in biology: If an organism has all the internal resources, along with an active tendency or disposition, to develop itself to the stage where it performs the functions specific to an organism of a certain kind, requiring only a suitable environment and nutrition for that development, then it is an organism of that kind, at an immature stage of its life cycle. Only thus can one recognize a chrysalis as an immature member of Lepidoptera, or a tadpole as an immature member of a frog species. Human embryos, whether they are formed by fertilization (natural or in vitro) or by successful somatic-cell nuclear transfer (SCNT — i.e., cloning), do have the internal resources and active disposition to develop themselves to the mature stage of a human organism, requiring only a suitable environment and nutrition. In fact, scientists distinguish embryos from other cells or clusters of cells precisely by their self-directed, integral functioning — their organismal behavior. Thus, human embryos are what the embryology textbooks say they are, namely, human organisms — living individuals of the human species — at the earliest developmental stage.
Neaves and Magill attempted to refute this argument by pointing to “tetraploid complementation.” But in this process, the iPS cells function as part of a distinct, developing organism, consisting of structures derived from both the iPS cells and the tetraploid cells. It is plain that the iPS cells do not survive the tetraploid complementation procedure, any more than sperm and egg cells survive the process of fertilization. Like the sperm or the ovum, the iPS cells function only as part of a larger whole.
Near the end of his comments, Bailey discusses “induced totipotent cells,” but in the course of his remarks, he reveals a failure to grasp the central question about them. We do not have to wait for scientists to produce such “induced totipotent cells” and speculate about whether they would be considered embryos; such cells already exist. By Bailey’s definition of totipotency (i.e., the ability to produce all cell types, including those of the placenta), many human tumors and all human embryonic stem cells and human iPS cells are “totipotent.” But although human iPS cells are able to produce all cell types, they are not able to organize
these cells into a coherent body, and therefore they are not the biological, moral, or ontological equivalent of embryos.
The truth is that iPSCs are not “totipotent” in the same sense that embryos are totipotent. Embryos not only make all cell types; they also orchestrate all the complex events of development needed to generate a coherent, integrated living body. And therein lies the characteristic that distinguishes embryos from non-organismal cells, including iPSCs. The artificial production of a totipotent cell capable of such an integrated developmental sequence has, of course, already occurred in cloning. Our point was that, so far, biology indicates that the production of a totipotent cell (a new embryo) requires factors derived from the oocyte (an egg cell). If those factors could be derived in some other fashion, their combination would generate a new entity, rather than allowing an already existing entity (such as a stem cell) to actualize an innate capacity. Yet even if that could be done, it would not negate our view of what constitutes an embryonic human organism; it would merely confirm, as cloning already proves, that there is more than one way to produce an embryo. So the Grail searchers would even then have to remain on their never-ending quest.
– Maureen Condic is an associate professor of neurobiology and anatomy at the University of Utah School of Medicine; Patrick Lee is the John N. and Jamie D. McAleer Professor of Bioethics and director of the Institute of Bioethics at the Franciscan University of Steubenville; Robert P. George is McCormick Professor of Jurisprudence at Princeton University.