The beginning of life: the statute of the embryo

The things I will talk about will probably help us in the later discussion of an issue which first came into scope a number of years ago and will continue to be discussed for many years to come because the Estatute of the embryo started with the Warnock Report and it still remains an unresolved issue. I will spend most of my Introduction time in describing human development. In fact, when I was preparing the paper I had originally intended to call it “The beginning of life: the estatute of the embryo” but, before going into the matter I would like to make some general considerations. In the first instance, let me say that the beginning of human life implies two fundamental questions: when that new life actually begins and when that human life, once it has started its existence, becomes individualised. These two questions can be approached from a biological perspective, from a genetic perspective, from the comparison and assessment of the embryo in evolution vs. the born baby. But also from a philosophical perspective which, in line with Zubiri, means that the “being” in development has reached “constitutional sufficiency”, that is to say when its personality, its uniqueness, is already characterised. Other authors claim that the human person “is” from the very moment of fertilization. Yet there are others who claim that a human being becomes a person much later in the development process....As you may see such vast range of opinions, beliefs or suggestions all make reference to how to apply Zubiri’s philosophical standpoint. I am not a philosopher myself and thus I will not defend that argumentation for fear of entering unknown grounds but, nevertheless, I do find this line of reasoning most suggesting.

Another preliminary remark I want to make is that in every biological process -be it at molecular or at evolution level- any biological phenomenon is continuous in nature. This means that it is impossible to determine the “before” and the “after” of an evolutional event in terms of a time scale. When people speak about the embryo and talk of the 14-day stage post fertilization one wonders why 14 days and not 13 or 15? I would like to stress on “continuity” as a fact in every biological process, even in fertilization. When does fertilization occur? When the spermatocyte approaches the zona pelucida to enter the oocyte? When the masculine pro-nucleous is released into the cytoplasm? When does cell cleavage start? Determining any one of those evolutional “whens” is just impossible. However, the very nature of continuity in the biological process is compatible with the spontaneous emergence of new properties and I can give you a number of examples to make my point clear. Say that we have 2 chemical molecules, two proteins. Each of them taken separately will exhibit its own properties and function. If we fuse those two proteins an entirely new function to their individual original ones will then emerge. However, the process itself was a continuous one. That then means that within the continuity of any development we should expect new things to spontaneously occur.

A third remark is that in a most general sense, when people discuss on scientific matters they tend to be quite reductionistic and do not distinguish between ordinary organisms and human beings. With regard to DNA, some people might be tempted to reduce the complexity of the concept “human being” to just a person’s DNA. The idea I want to launch here is that reductionism in Biology is quite a risky business because the biological “whole” does not equal the summation of its parts. That might have something to do with ordinary practice in laboratories: looking at life, or at the human being under the scope of a single lens. Too reductionistic.

Having made these general remarks, I will move into a few particularities with regard to human embryo development from the genetical and biological perspectives.

The process of development can obviously be subdivided into a series of stages: on the one hand, (conventionally ordinating them) we have the stage gamet-fertilization-zygote. Then comes the stage zygote-morula-blastocyst-hatching (of that blastocyst on the uterus walls). A third stage would follow from the end of the hatching period to the fetus stage to the moment of delivery itself. All these stages are distinct biological events whose ethical and juridical treatment is different in the same manner.

From the perspective of genetics, again in my opinion, the most crucial stage is the second one (in the order that I have listed them): zygote-morula-blastocyst-hatching because it has straight link with the issue of our concern, the Estatute of the Embryo, and as I will soon explain it is in that stage when we can still question the individualisation of the new being. Consequently, that is the reason why people either in favour on embryo manipulation or in favour of getting rid of cryopreserved embryos claim that the embryo has no Estatute because its characters of individuality have not yet appeared and thus ethical considerations are unnecessary. This argument is very much significant from the juridical perspective as well.

The terminology in use has been subject of much controversy (Dr. Palacios, who has sat in many different discussion forums has great experience).Whether we should speak in pre-embryo terms or refer to this entity in terms of “pre-implantational embryo”. The truth is that since 1988 -at the time when the Spanish Law on Assisted Human Reproduction was underway and the so called Palacios’ Report was presented- terminology has been the focus of attention.In my opinion and with regard to the likely ethical consequences that one given term might have upon people’s attitudes and ideas when discussing scientific progress is significant enough to consider the matter in depth. The simple fact of using the term “pre-embryo” changes the whole perspective in people’s minds because as it has not yet reached embryo status, it is not worhty of protection under the Estatute and can therefore be handled, manipulated or whatever. Other people prefer the term “pre-implantational embryo” or a 2-cell embryo, or a 4-cell embryo or a 16-cell embryo.

International literature, both scientific an juridical, compiles a great many contributions from different authors and expert Committees in which different terms have been used to describe the same biological reality. In my Introduction I intend to analyse both from the scientific as from the ethical perspectives whether a pre-embryo is nothing else but a conglomerate of human cells or if that cluster of cells actually carry the characters that make it a unique human being. Were this so, ethical considerations should be imperative.

I said before that from the genetics perspective the most important stage in the evolution of a human being is the second one, from zygote to hatching in what regards the questions of when a human life comes into being and when that human life becomes individualised, that is, when the new entity acquires the features of unity and uniqueness. From the biological and genetic perspectives there is no doubt whatsoever that “the new life” as a new human entity will come into being at the very “moment” of fertilization -bearing in mind the continuous nature of processes in Biology- because it is then that the newly formed zygote comprises genetic information resulting from the fusion of two distinct entities (the two gamets) to become a third entity (the “tercium”, a term sometimes used in juridical documents). This new entity carries genetic information which is strictly human, that is, the resulting product of its natural course of development will be a human beig not an apple-tree nor an elephant. Once having said this, the following consideration is what happens next. And what happens next is that two biological phenomena can occurs during the development of the embryo which has just come into being and these can actually alter the course of things with regard to the properties of unity and uniqueness I mentioned before. Unity as the quality of being one entity and uniqueness as the quality of being different from any other entity.

Unity has a lot to do with what Prof. Egozcue illustrated us on: chimaeric entities. Well, zygote-chimaeric or post-zygote chimaeric entities may result, the former being produced as results of double fecundation, that is, the oocyte and a polar body fuse and result in two distinct genetic information entities that fuse and produce an individual whose cells carry different genetic information. Or it may be that two embryos at a very early stage of development (say 4-8-16-cell embryos) fuse. I am trying to make you understand that embryo fusion is an event which can spontaneously occur at a very early stage of embryo development but fusion is unlikely once the embryo has started configuration of the future nervous system,when the primitive neural crest appears. After that particular moment in the evolution of an embryo fusion is no longer possible. But where and how to delimitthat “moment” in the time scale? It has been fixed at day 14 post-fertilization, just after hatching has actually taken place. The same could be said with regard to “unity”, and when monozygotic twinning spontaneously occur (zygote splitting) resulting into 2-3 monozygotic babies, the splitting seems to take place in the same time period. That would then mean, again from the perspective of genetics, that “unity” and “uniqueness” do not become defined until day 14 post-fecundation and this is a fact accepted worlwide.

GIJÓN (Spain), Scientific Committee Meetings on 7th and 8th May 1999