Recent Science and the Personhood of the Human Embryo
Dylan James FAITH Magazine January-February 2010
Fr Dylan James Parish Priest of Shaftesbury, Dorset, and Moral Theology Lecturer at Wonersh Seminary Surrey argues that the 2008 Human Fertilisation and Embryology Act radically failed to reflect the implications of recent science. This is a focussed update of his longer March 2007 article.
It's now over two decades since the Warnock Report of 1984 led the way in approving experiments on human embryos in Great Britain. Back in 1984 many scientific claims were made to justify the 14-day time period that was given to experiment on embryos. More recently, the UK government's Human Fertilisation and Embryology Act of 2008 has extended embryo experimentation while working on the assumption that the 14-day time frame can be accepted as a starting point. However, recent science undermines the claims that were initially made for Warnock and this article will outline some points which indicate why the government should have re-thought the Warnock position and not used it as a foundation.
Before looking at the science, it must be noted that the notion of a "person" is a philosophical concept and not a scientific one. Similarly, which "rights" we should accord to persons is an ethical matter and not a scientific one. However, science is very relevant because it shows us whether or not the embryo meets the criteria which define a person. Catholic bioethicists typically use the definition of the person proposed by Boethius in the sixth century: "a person is an individual substance of a rational nature". Turning this into a set of scientific criteria, this means that a human person must be an "individual" and thus a basic question that needs to be asked about the early embryo is whether it is just a loosely-related collection of cells or whether it is properly an "individual". Scientific data now implies that the transition from egg and sperm to a new individual takes place within minutes of fertilisation beginning. Of course, none of this is likely to convince the hardened utilitarian who merely cares about the greatest good for the greatest number and does not care about whether it is a person he is experimenting on. But most people don't appeal just to utilitarian calculus and neither should our legislation.
1. First, let us recall what the Warnock Report took as being scientifically established. In the 1980s it was claimed that the cells of the early embryo were "undifferentiated" and that the embryo was thus no more than a "loose collection of cells". The supposed evidence to back this claim was that (it was then thought) it is not yet established which cells will become which types of future tissues, e.g. which will become the placenta and which will become heart cells. The early cells were referred to as "totipotent" meaning that any one of them could become a whole new individual if separated from the cluster. It was thought that the cells only become differentiated at 14 days when the primitive streak (the early backbone) forms. As evidence of the undifferentiated status of the cells, it was pointed out that up until the formation of the primitive streak at implantation the embryo can divide and form identical monozygotic twins. It thus seemed to Warnock fair to claim that prior to 14 days there was no "individual", there thus could not be a "person", and so it was ethical to experiment on the early embryo. Standard literature thus came to call the pre-implantation embryo the "pre-embryo" to indicate that it was judged to have a significantly different status to the later embryo.
Since the turn of the millennium, however, embryology has been aware of the "positional information" possessed by the cells of the early embryo. This means that the cells are not as "totipotent" as once thought and that the cells are in fact already differentiated at the two-cell stage with it being largely determined which cell's progeny will form the "embryo proper" and which cell's progeny will form extra-embryonic material like the placenta. This positional information is established by the position of the initial sperm entry point, at fertilisation, long before the formation of the primitive streak at 14 days. It is the position of the sperm entry point that establishes an axis that determines where the initial cell will divide into two cells, where the position of the primitive streak will be, and thus where the backbone will form. There is thus a direct line of continuity from the position of the sperm entry point to the future adult body. Further, we also now know the speed and manner in which the ovum's outer membrane changes to repel further sperm penetration, a process that establishes the zygote as a closed system. This process takes 1-3 minutes from initial sperm penetration of the outer membrane.
2. This said, what of the claim that the capacity of the pre-implantation embryo to divide into twins means that it cannot be an individual? As the philosopher Prof. Kevin Flannery SJ has noted, a divisible individual is still an individual, and a "divisible individual" is not a contradiction in terms. As Aristotle observed, many living individuals are divisible into two or more other living individuals, like plants or flatworms. Being divisible does not stop you being a living individual. Of course, what happens to the identity of the pre-existing individual is unclear. If the initial zygote possesses a spiritual soul, what happens when the embryo splits? Does the original embryo die and its soul get replaced by two new souls in the two new twins? Or does it continue and a new person split off from it, with its newly created soul? Or is twinning the result of an internal materially determined factor that would indicate that there were two souls present from fertilisation onwards, each relating, in their own specific manner, to the one physical, organic unity of cells?
Though such questions cannot be easily answered, Nicanor Austriaco OP has argued that the first explanation corresponds better to some of the scientific data. What scientific data might indicate whether or not the embryo starts out as an individual person that is then destroyed in the division that produces two new individuals or whether it starts out as two closely related persons destined-to-twin? If the first scenario holds, then twinning would seem to be some form of defect in the program of development and if this is the case then we would expect to see some other signs of defect. This is, in fact, what we do find, with identical twins suffering from a statistically significant greater number of birth defects, defects ranging from indeterminate sex to anomalies of the tongue to Down syndrome. The fact of these defects does not easily accord with the second two scenarios and suggests that the first scenario could be the philosophically correct way to interpret the situation. This said, recent studies from the Mio Fertility Clinic in Yonago, Japan have suggested that it may be possible to predict which embryos will divide into twins. The research on this point is presently inconclusive, but, if this is true, then it would seem to follow that the third scenario outlined above is the correct interpretation. In short, we don't yet have enough scientific information to be confident in determining which of the three philosophical interpretations is correct.
Nonetheless, whether twinning is the result of an individual that becomes two individuals or is the result of a cell cluster that was already two individuals but looked like one, the potential of the pre-implantation embryo to divide does not imply there is not already an individual present (or two individuals present), an individual who is a person with rights. Despite the fact that we don't presently fully understand the factors that lead to the phenomenon of twinning, its existence as a relatively rare phenomenon does not give us grounds to deny the early embryo its personal rights.
3. Having said that the cells of the early embryo are already differentiated, it must be noted that before the 14-day stage the cells do still have a certain "plasticity" in that they can be re-programmed to another differentiation: the positional information they once possessed seems to be destroyed by their being separated from their cluster. None of this suggests, however, that the cell cluster was not an individual prior to such a change, nor does it suggest that more individuals appearing in twinning is a philosophical problem.
Another aspect of the "plasticity" of the cells of the early embryo can be seen in the formation of chimeras. A chimera is a creature that has cells of a different DNA in different parts of it. In Greek mythology the chimera had a lion's head, a goat's body and a serpent's tail. In modern science chimeras have been created with mice by merging together two different embryos when they are at the cell-cluster stage. Amazingly, the cells seem to re-differentiate themselves to form one new embryo that will mature into an adult mouse that has some parts of it with one set of DNA and other parts with another set of DNA-black and white mice embryos have been combined to produce this in a visual way. This phenomenon seems also to occur naturally and some humans have been found to be such chimeras with different DNA in different parts of their body. One thing this indicates is that DNA is not as central to individuality as was once thought: some writers used to claim that the early embryo was an individual because it had established DNA, however, the existence of chimeras suggests that DNA is not a precondition of individuality. In fact, the previous paragraphs have argued that individuality is established within 1-3 minutes: well-before DNA is established.
4. One final scientific issue: some sceptics of the personhood of the early embryo point out that the embryo suffers from a very high mortality rate. Some estimates claim that as many as 50% of embryos do not survive to birth. If all of these embryos are persons and thus have immortal souls, is heaven really full of people who never even achieved birth? This may seem like a startling concept.
In considering this it is worth noting that many "lost" embryos are not real embryos at all but are rather "pseudo-embryos" and that this is why they are expelled from the womb. While science's ability to analyse this is still developing, Austriaco illustrates the issue by arguing that "complete hydatidiform moles" are such non-embryos while "partial hydatidiform moles" are embryos (but disabled ones). But in the final analysis it should be noted that for much of human history infant mortality has approached or exceeded 50% and thus this also suggests that heaven is full of people who never achieved adulthood. No Catholic would conclude from this that the baby at the breast is not a person worthy of full respect and protection. Similarly, the high mortality rate that embryos suffer from is no reason not to consider them to be persons.
5. Finally, when all is said and done, it must be conceded that a debate remains. Though science today gives us stronger reasons to argue for the personhood of the early embryo than there were two decades ago, some people still doubt the pre-implantation embryo's personhood. How then should we proceed in the face of doubt? When dealing with the rights of others, the Congregation for the Doctrine of the Faith in 1974 identified an important moral principle when it reiterated that, "It is objectively a grave sin to dare to risk murder". If a deer hunter sees a bush moving he cannot shoot until he is morally certain that it is a deer and not a person who is moving it. The basic point with respect to the embryo is that recent science has shifted the burden of proof strongly in favour of the notion that an individual is established at fertilisation and thus strengthens the philosophical position that a person is instantiated this stage. It follows that the risk of murder is even clearer now that it was when the Warnock Report was produced in 1984. The fact that the 2008 Human Fertilisation and Embryology Act failed to recognise this is much to be regretted.