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Embryo mens vanaf conceptie : 3. Intrinsic criteria
Geplaatst door mgr.dr. W.J. Eijk op 28-02-2006 (2744 gelezen)
Embryo mens vanaf conceptie

Intrinsic criteria

From what has been said above it may be understood that one can employ intrinsic criteria alone to establish a definition of an embryo as a human individual and that these criteria must take into consideration the biological data as well.

The independence of the body from the mother: the embryo becomes a human individual when it is no longer a part of the organism of the mother

At the end of the 1960s and during the 1970s feminist groups upheld the right to procured abortion with the motivation that the unborn child forms a part of a woman’s body and thus a woman should be able do with it as she so pleases – ‘we are the governors of our tummies’.

This is not a new argument. Roman law laid down that an unborn child, given that he or she was still a part of his or her mother or her organs prior to the act of birth, was not yet a citizen with all connected rights (Ulpian, a Roman jurist, d. 228 AD).[18] This idea was also to be found in other peoples of that age, for example the Jews, and thus Roman jurists held it to be an element of the jus gentium.[19] The Stoics (Hempedocles) compared the relationship between the embryo and the womb to the relationship between a fruit and its plant: the fruit, until it falls or is picked, is a part of the plant. In the same way, before birth the embryo could not have its own existence separately from the existence of the mother. The embryo was said to acquire a soul when it began to breathe, that is to say a little time after birth, but not before birth.[20]

The discussion about the status of an embryo during the first seven days concerns, first and foremost, the ethical problems of in vitro experimentation on an embryo that has been created by artificial fertilisation and thus is not a part of its mother. The biological data provided by modern science, however, have made clear that the embryo, beginning with conception, has its own existence. It relies on its mother for food, liquids and the expulsion of organic matter. However, its development and its growth as an individual are guided from conception onwards by its own genome, which is different from the genome of its mother. For this reason, on the basis of contemporary genetic knowledge, one can in no way argue that an unborn child is a part of the body of the mother. On the basis of this argument it is not admissible for the mother to claim the right to dispose of the life of the embryo.

Human biological nature: the embryo is a human individual because of the simple fact that it is biologically a human being

The Wilkes based their rejection of procured abortion on the fact that human life, from a biological point of view, begins with conception. For them, theology and philosophy were of no use in solving the question of the status of the embryo given that in both disciplines there exist many divergent opinions on the subject.[21] The biological definition of the beginning of life, that is to say conception, which cannot be called into doubt by anyone, was, in the view of the Wilkes, thus the most solid criterion by which to attribute a moral status to the human embryo starting with conception.

This conclusion, however much it may be held to be interesting by the ‘pro-life’ movements, meets certain objections that are insuperable. It does not take into account the fact, for example, that, as will be seen below, many modern ethicists make a distinction between human beings in a strictly biological sense and human persons. The embryological and biological facts, in themselves, interpreted in various ways in the various visions of man, cannot provide a definitive answer about the status of the embryo. According to certain visions of man it is to be excluded that the embryo is a human being from conception. In addition, a purely biological definition would lead to a biologistic and materialistic conception of man which holds that man cannot have an intrinsic dignity but at the very most an instrumental value. An appeal to the mere biological presence of a human being, leaving aside other aspects such as the spiritual dimension and its intrinsic finality, is insufficient, as we will see below.

Individuality: the embryo becomes a human individual only from the moment at which it cannot divide itself and thus give life to a twin or unite itself to another embryo

In England in 1990, on the recommendation of the Warnock commission, a law was passed that allowed experiments on in vitro embryos on certain conditions until the fourteenth day after conception. In its report, which was published in 1984, this commission concluded that the early embryo, because it still had the possibility of dividing, could not be considered as being an individual being and thus could not be considered as being a human individual either.[22] Even some Catholic ethicists have adopted this approach.[23] The moralist Häring has stated that: ‘the greatest objection to the theory of animation at the moment of fertilisation is raised by the phenomenon of identical twins’.[24]

The Warnock commission held that the beginning of the individuality of the embryo was the moment of the formation of the primitive streak, after which the embryo is no longer able to divide into two individuals that are genetically identical. The primitive streak is the oblong concentration of cells at each end of the embryonic disk which emerges on the fourteenth or fifteenth day after conception. It is the first manifestation of the anteroposterior axis of the embryo and appears in the place where the nerve tube will develop after a short period of time, and from which the brain and the spine will form. In this place a number of strata of differentiated cells form after their migration. At the most two primitive streaks can form in the embryonic disc but because of the differentiation that has just begun this will not lead to the division of the embryo.

This period of two weeks coincides roughly with the period before the implantation of the embryo in the mucous of the embryo, which is completed between the eleventh and thirteenth day after conception. Nowadays, reference is often made to a ‘pre-embryo’, a term that suggests that the embryo is not yet a human individual and thus does not deserve to be respected as such.[25] This line of reasoning has its origin in the presumption that the embryo is not an individual as long as the possibility of scission exists and thus cannot even be considered a person because a person is the most complete individual being.

The question is: does the possibility of the separation of the embryo really exclude its individual being and thus its being a person? There is another interpretation that is possible, that is to say that man is able to procreate in an asexual way until the formation of the primitive streak. When I, when digging in the garden, cut a worm in two, both the parts of the worm carry on in their own way in an apparently undisturbed fashion. It appears a rather unattractive thought that something of the same kind can happen in man, but who can prove that the contrary is the case?

That asexual procreation is possible in man as well would appear to be demonstrated, or so assert Ashley and O’Rourke in the third edition of their textbook Health Care Ethics, by scientists who are able to clone human adults, who are without doubt seen as persons, through nuclear transplant.[26] We now know that is a concrete possibility given the success in the application of this technique to human beings. In the month of February 2004 a team of researchers at the National University of Seoul (South Korea) managed to produce thirty embryos from two-hundred and forty-two oocytes by using the method of nuclear transplant.[27]

A further argument that is said to exclude that the embryo during the first stages of its development is an individual focuses on the possibility of the recombination of embryos. In experiments with animals it has been demonstrated that it is possible to combine two or at the most three embryos into a single embryo that contains genetically different cells which come from the original embryos.[28] The discovery at the end of the 1960s of the existence of men with cells with a twofold chromosome X and cells with one chromosome X and one chromosome Y was an indication that recombination also takes place in human embryos.[29] But not even this phenomenon constitutes proof that the embryo during the first stages of its existence is not an individual. One could also well object that in the case of the recombination of the two embryos the body of one has been absorbed by the other, which managed to conserve its individuality, and thus the first embryo ceased to exist as an individual and died from a metaphysical point of view.

Many people see proof of the individuality of the early embryo in the fact that the composition of the genetic material of the chromosomes is established at the moment of fertilisation. Others object that the development programme that the chromosomes contain is not immediately active after conception. At the outset the energy in the embryo is provided by the Altmann’s granules, which come from the mother. Thus the development of the very first stages of the embryo is not guided by the DNA of the zygote but by the DNA of the Altmann’s granules which come from the mother, from the messenger RNA and from the proteins that were present in the spermatozoon and the ovule.[30] This, too, is not in itself a valid reason for doubting the individuality of the embryo. The development programme in the chromosomes, although it becomes active immediately or after only a few days, is established from conception onwards and will guide or regulate the successive development of the embryo if factors of disturbance do not intervene. The results of the most recent research indicate, however, that the DNA of the embryo begins to guide its development practically at the zygote stage, when a first gene that is responsible for gonadic differentiation is already active.[31]

The criterion for the individuality of the embryo is often likened to the criterion which observes that the embryo will become a person. This point will be discussed later in this paper. This implies that the embryo cannot be considered a person until it is an individual, an assumption that in itself is obviously right. Thus it is that Ford identifies the formation of the primitive streak with the moment of animation.[32]


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