An emerging consensus is that somatic cell nuclear transfer (SCNT) for the purpose of creating a child (also called “reproductive cloning”) is not acceptable for both moral and scientific reasons. In contrast, SCNT with the goal of generating an embryonic stem (ES) cell line (so-called “therapeutic cloning”) remains a controversial issue. Although therapeutic cloning holds the promise of yielding new ways of treating a number of degenerative diseases, it is not acceptable to many because the derivation of an ES cell line from the cloned embryo (an essential step in this process) necessarily involves the loss of an embryo and hence the destruction of potential human life.

In this chapter, I develop two main arguments that are based on the available scientific evidence. First, in contrast to an embryo derived by in vitro fertilization (IVF), a cloned embryo has little, if any, potential to ever develop into a normal human being. By circumventing the normal processes of gametogenesis and fertilization, nuclear cloning prevents the proper reprogramming of the clone's genome, which is a prerequisite for development of an embryo to a normal individual. It is unlikely that these biologic barriers to normal development can be solved in the foreseeable future. Therefore, from a biologist's point of view, the cloned human embryo which is to be used for the derivation of an ES cell and the subsequent transfer into a patient in need has little if any potential to create a normal human life.