Embryos, stem cells and moral status: a response to George and Lee.

In an earlier essay, we argued that those who grant a special moral status to human embryos cannot consistently refuse to grant a similar moral status to other entities, such as stem cells, that also have the potential to develop into adult humans (Sagan & Singer, 2007). To do so, however, would have absurd implications. In a recent issue of EMBO reports, Robert George and Patrick Lee defended their attribution of special moral status to the human embryo against our argument (George & Lee, 2009). But their defence fails. In making the case that a stem cell is an entity with the potential to become an adult human, we suggested that when a cell is transferred to an enucleated egg, we should regard the cytoplasm of the egg as the environ ment in which the cell develops. In rejecting our contention that the stem cell is such an entity, George and Lee deny that the cytoplasm is merely the environment in which the cell develops. They wrote: “something that qualifies as ‘merely environmental’ does not enter into an organism and modify its internal parts resulting in an entity with a new developmental trajectory.” This statement appears to overlook the fact that, at least from implantation onwards, there is a constant acquisition of substances from the outside that modify the embryo’s internal parts, including its gene expression (Waterland & Jirtle, 2003). In our article, we speculated that further advances in science might help to resolve what is crucial for development into an adult organism. Indeed, researchers recently created mice from reprogrammed cells (Zhao et al, 2009; Kang et al, 2009). No egg cytoplasm was used. This clearly demonstrates that even somatic cells alone have the potential to become an adult human being. George and Lee might reply that when reprogramming cells, the new being comes into existence only after the reprogramming is complete. But such a response would miss the point that the potential was there before the cells were reprogrammed. If we are concerned about moral status, then it is hard to see why the embryo should have a moral status that is markedly superior to that of the reprogrammable cell, just because it is one step further along the path towards becoming, if everything goes well, a mature human being.