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Embryonic Development

Tactile-kinesthetic experience is virtually impossible in the early stages of gestation, but there is a rough time-frame in which the rudimentary human brain grows and forms greater capacities for experiencing tactile-kinesthetically, an experience which is the foundation for a sense of self. At 3 weeks old the central nervous system of an embryo begins to develop and the heart begins to beat. By the 5th week the central nervous system is more sophisticated, and at 7 weeks old, simple neural activity is detectable in the embryo. At 18 weeks the cerebral cortex has developed for synaptic connection. (During this development, a fetus seems to be morally equivalent to a comatose human, brain activity in both being equally simple, were it not for the fact that the fetus has more potential than many comatose patients do.) It is not until the 24th week that nerve transmission takes place within the fetus (Singer, 1993), allowing for greater tactile capacities, including a sense of pain. Anaesthetization could eliminate the problem of pain in aborting a 24 week old human life, but it is the ability to feel pain that is morally significant because it emphasizes the fact that the fetus has more human faculties and is closer to birth, lending moral weight to its life - though it should be noted that at this time the fetus is in a brain-state much like sleep, so it can hardly have a developed sense of self. However, this biological fact does not mean that the capacity for some sort of experience does not exist; thus this simpler form of experience is of moral concern, especially when the fetus is on the threshold of sophisticated tactile-kinesthetic experience and consequently a sense of self.

But regardless of the ambiguities present in gestation, we do know that a zygote is a simple cellular structure of a very small number of cells where not even the embryo and placenta have differentiated. Here, human life is at the beginning of gestation - the germinal stage. A zygote is obviously not equivalent to a fully-formed fetus or an adult human being because we are dealing with something very simple and very small. As the germinal stage develops into the embryonic stage, human life becomes increasingly complex and as the embryo grows into the fetal stage it becomes a smaller version of an infant, having growing tactile-kinesthetic powers and sense of self.

Taking into account the problems of the "potential argument", the morality of embryonic destruction should be partially defined by the facts of biological differences in stages of development. Therapeutic cloning or using cryopreserved zygotes are the most morally permissible methods of embryonic destruction because only a simple cellular structure is destroyed and the cells taken from it will be very useful, if not life-saving, to the patient. Aborting pregnancies at this stage is equally morally permissible for the same reason - only something very simple is destroyed. But the uses or abortions of embryos in the fetal stages of development are less permissible because the embryo is arguably a human being, having all of the basic faculties of the body, in comparison with the germinal stage embryo. The morality of the surgery in this case is mostly a matter of whether the circumstances surrounding the woman carrying the fetus can justify an abortion.

It has recently been reported that Colin McGuckin of Kingston University in Surrey, UK, announced the discovery of stem-cell like cells derived from umbilical cord blood (known as CBEs). These are not the same as embryonic stem-cells, but they appear to be much more versatile than adult stem-cells. Though the discovery has not yet been published and peer reviewed, the announcement shows that science often finds ways of circumventing ethical dilemmas. If CBEs are just as useful as totipotent stem-cells, then there will be no need to use embryonic sources of stem-cell. However, the moral debate cannot be entirely put aside because understanding the moral status of the embryo is still necessary for informing acts like abortion and possible future acts like transplantation into artificial wombs, or the continued use of embryos for scientific research.

Forwards to The Ethics of Late Ontogeny - Aging

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