The moral significance of pain for synthetic human entities derived from embryo-like cells

Recent developments in stem cell biotechnology are challenging afresh the longcontested question of the moral status of nascent human life. Rather than clarify the moral question, more detailed information about and ability to manipulate the subcellular realm have further complicated the ethical analysis. One of the greatest ethical challenges is how to evaluate novel entities that do not fit within the biological frameworks that guided the development of current consensus about ethical boundaries for the creation and destruction of embryonic human life, whether for purposes of reproductive embryo selection, embryologic research, or the development of cellular therapies in medicine. Amid claims that the 14-day rule, defined by the appearance of the primitive streak, has become obsolete, some scientists have proposed that the capacity to experience pain should be the new moral threshold beyond which novel organisms should not be allowed to develop. This leads to further questions about the moral significance of pain, the minimum biologic substrate needed for pain to exist, what kinds of experiences count as painful, and how to detect and measure pain in creatures that cannot speak.