Unity of Scientific Evidence and Teaching of the Catholic Church

Dr. (Ms.) M. A. Peelers and Dr. Jerome Lejeune

Human Life - Human personhood. Ed : G. S. de Souza et C. S Vas - Bombay 1990.




It is curious to note the discrepancies and confusion which seem to surround the definition of the human person. Never in man's history has there been so much scientific evidence, such understanding and discoveries which have firmly established that at conception a new human being is created.

The confusion stems from four errors:

The first comes from the arbitrary definitions and characterization of what constitutes a "homo sapiens". It is apparently extremely difficult to grasp the concept that human person, human individual, human being and human life constitute a unified entity. One cannot be a human person, a human individual without enjoying human life, nor can one have human life. be a human individual without being a human person. This is part of the human condition and holds true for any stage of one's life. The fragmentation and breakdown of what normally constitutes a whole has given rise to confusing definitions: the term human person which escapes any clear definition ... which has something to do with relationships, acceptance by others, being a rational being and which begins at some undefined point of one's life (perhaps only well after birth if one underlines the "rationalis natural" aspect or perhaps even never, if one needs to be accepted by others in order to be a person); the term human individual which begins at nidation and the term human life, sometimes abbreviated to life or life which begins at conception.

- The second error comes from the unscientific discussion of scientific data.

- The third error stems from the sudden rediscovery of the theological explanations of medieval biology.

- Last, but not least, is man's desire to be his own master ... deciding over life and death. The deliberate "blurring" of the evidence: "a man is a man/is a man" ... is perpetrated with the sole purpose of forsaking moral duty.

In this presentation we would like to review currently known scientific data and to demonstrate that they do not in themselves constitute the slightest objections to the teaching of the Church on these matters. We would then like to present a brief synthetic view conform to both scientific evidence and traditional Catholic teaching.


Scientific considerations

The chromosomal set-up. 23 chromosomes from father and 23 chromosomes from mother can be compared to the magnetic tape on which the "code" of an entire symphony is written.

The mitochondrial DNA (purely of maternal origin) and the enormous stock of pre-fabricated cytoplasmic RNA (also of maternal origin), together with all the structural information of the egg (protides, lipids and sugars) can be compared to the "tape recorder".

The nuclear DNA, inside the chromosonal set is the mini-cassette, the cytoplasmic DNA and RNA are the "walkman". The result is thus: - the sperm alone does not make a man - the egg alone does not make a being but sperm and egg mixed together inside one zona pellucida make one human being. The zona pellucida is the message which proclaims: "This is a single individual. It persists up to the moment when cleavage of the cellular mass is no longer comparable with twinning.


The Zygote

In humans, the one by one process is the norm but because monozygotic twins exist, there can be a message indicating: this is a twin set from the very moment of sperm entry. This is the rule amongst the armadillo (tattoo). Some species have 4 embryos out of one egg, others 6, others 8 and even 12. The number is genetically fixed and hence it must be built-in from the moment of conception.

The message in somatic cells is surely modified as compared to the message, at the moment of conception, methylation and demethylation of DNA is a biochemi-cal demonstration of this.


Biological problems encountered:


1. Twinning :

Two types of twins are known. Dizygotic twins arise from the fertilization of two separate ova by two separate spermatozoa. They are therefore sibs of the same age. The fact that they spend their early life together in the same uterus. does not change their personal make-up.

Monozygotic twin formation has been raised as evidence that. At conception, one may only speak of human life, not of human being, since two human beings arise from one conception. Let us however examine the facts.

Monozygotic twins are uncommon (around one in three hundred births). (1) (2)

Classical embryology teaches us that monozygotic twins may arise until the fourteenth day following conception. It must however be underlined that. in the human species, the reasons for the above statement are hypothetical deductions and to explain differences of placenta, amnions and chorions (common or separate). (3) There is however no biological proof indicating that, in humans, twinning may occur at different times following conception and up to day 13-14.

Monozygotic twinning is thought by many scientists(4) (5) as resulting or being influenced by the fertilization of an over- ripe ovum that is. a slightly defective ovum. Therefore. the ovum contains at the moment of conception, the genetic information which leads to the formation of monozygotic twins. It is well known that genetic information, even though present at conception may only manifest itself much later on in life. For example, the gene responsible for Huntington chorea is present at conception but the disease will only manifest itself some 40 years later (and at that stage one does not suddenly become another human being). The message for two human beings is therefore present at conception. Having shared so intimately the beginning of their life together, monozygotic twins share one nature. The human process resulting in monozygotic twin formation is therefore distinct from, for example, the formation of "twins" in amoeba. In this case, the splitting of one amoeba gives birth to two identical sister amoeba. If such were the case in human monozygotic twinning one could understand the theological objections raised : How can one soul be split into two? However since. in humans, identical twin formation seems to result from a message contained at the moment of conception this does not, conflict with classical teaching of the Church.

At the frontier between twinning and chimera formation is the issue of embryo splitting (at the blastomere stage) with secondary aggregation chimeras. This has been reported in animals especially in a mouse experimental model (6). It must be noted that this manipulation can only work if the "half" embryo is placed again within another zona pellucida.


2. Chimera formation:

The problem raised by chimeras is even less of a problem.

A chimera arises probably at foundation: An egg, split in two cells inside one zona pellucida (probably by non-expulsion of a too big polar body) is fertilized by two different sperms. Hence, the same individual (due to the plastic bag of the zona pellucida) is carrying two different genetic make-up. But they start the life together at the three cell stages : Hence the result can only be one person. There is no theological contradiction in the fact that "a person can have two natures". Blood chimeras, often brought forth as an insurmountable objection to human beings beginning at conception, is simply the friendly exchange of blood between twins through the placenta (7) (8). This occurs fairly late during the pregnancy. Hermaphrodite formation, on the contrary occurs at conception (9) (10). A female pronucleus is fertilized by one spermatozoa while the second polar body (of the same ovum) is fertilized by another giving rise to one human being contained in one zona pellucida. Other chromosomal anomalies secondary to anomalies at conception are known but since they occur at the moment of conception they cannot be raised as objections to conception being the beginning of a human being. The fertilization of one ovum and of its polaire body (part of that one ovum) by two spermatozoas and when the process occurs within one zona pellucida, can by the nature of the process only give rise to one human being. It is therefore completely distinct from the notion of fusion of two human beings with annihilation of one of them.

The case described by de la Chapelle et al (11) is totally conform to such a process (in this case fertilization of a female pronucleus and of its first polar body could explain the biological observations). No case of spontaneous fusion of two embryos into one individual has ever been demonstrated in man.


3. Totipotentiality of early embryos:

There seems to be some confusion regarding the notion of totipotentiality of cell lines as compared to early human development. Totipotent cell lines are highly artificially, viral-induced modifications of normal cells. When these cells divide they give rise to daughter cells, then grand-daughter cells, then great-grand-daughter cells, all of them being identical etc... until they start degenerating and dying. Their only potential is to divide, to give more of the same ... 100 pounds of HeLa cells will never reconstitute the human person of Helen Lane. As the nursery rhyme goes: ... "and all the King's horses and all the King's men could not put Humpty-Dumpty back together again!"

The totipotentiality of the early human being is quite different. Each successive division brings about more and more somatic organisation.


4. Epigenetic factors:

External influences, though important must be placed in their right perspective. Although they can alter, even quite significantly the development of a human person (for example German measles can cause mental retardation of a fetus conceived normal, a car accident can cause permanent brain damage ...) they can at no point make another human being or turn a human person into some other species. Being subject to external influences is part of our human condition.

The epigenetic factors which influence gene activation or inactivations can be compared to lights being turned on and off in a house as the need for them arises. A given genetic message can be used at different times of development but in the original message. (Hemoglobin switching is a good example of this.)


5. Early loss of pregnancy:

It is generally thought that the total rate of pregnancy loss after implantation is around 31 % (12). Of these a high proportion seem to be due to fetal chromosomal anomalies.

We would like to underline that the term fetal wastage is often used when talking about early loss in pregnancy. This brings us to an important consideration. If one accepts the Catholic teaching that man is created in the image of God and that our final and only predestination is that of seeing God, of being given the heritage of son's of God, then the term of fetal wastage becomes one that is offensive in terms of human dignity. Furthermore, we realize that our "logic" has become clouded over by our materialistic thinking. Value is seen only in terms of the finished product not in terms of God's tender love. Indeed it seems that greater value is given to a human person who has achieved something, has gained material wealth or fame and not in terms of our true heritage. Waste of human lives is also spoken about in regards to the earthquake victims in Armenia, of hunger victims in Africa, of neonatal deaths etc... No human person can even be regarded as "wastage". Although it remains a great mystery that some human beings die very young, it must be remembered that the time of our death remains a mystery for each one of us and that rather than looking at this reality from a negative prospective we must always remember to what heritage we have been called and from what tender divine love we have been begotten.

These two considerations have been the basis of theological discussions - long before genetics could refine the corresponding biological concepts.

If a person is defined as "capable of rational consciousness", a very generally agreed definition, then:

1) Only a human zygote can develop itself into a being able to enjoy eventually rational consciousness

2) No other zygote (non human) has the same capacity

3) Hence the zygote has the "capacity of rational consciousness".

The counter arguments are biologically interesting:

If the "thing" develops itself out of the sole maternal genetic make up, what is it? It is a dermoid cyst of young virgin girls or an ovarian teratome. It contains skin, teeth, hairs, hence it has achieved the whole differentiation process making specialized tissues. But it has no organization into organs, no organization into a "being". Hence the maternal chromosomal DNA + the maternal cytoplasm is enough to build all the spare pieces but not the being.

Conversely, if the "thing" develops itself out of the sole paternal genetic make-up, what is it? It is an hydatiform mole. It makes tiny cysts, again and again, but nothing else.

Judging from these two well known mishaps of fertilization it means that maternal contribution is the building block and paternal contribution is the individuation. But no individual can be build if there are no building blocks available, and no individual can be build either if only the building blocks are available.

These biological counter examples of the normal fecundation are pointing in the same sense than the physiologically normal process: If a fertilized egg contains the whole genetic and cytoplasmic information typical of the human nature then this being, being human, is a human being.


The importance of establishing a clear definition of the human being :

From a scientific point of view there is no doubt that at the moment of conception a new human being is brought into existence. There can be no doubt that "it" is human and that it is already much more than a form of human life.

If one introduces ambiguous terminology, if one attempts to dissociate human life from human being, from human person, one opens the door to ambiguous notions about the human person and about respect for the human person. One must therefore approach this matter with the seriousness that it deserves. Suggesting that perhaps one should consider only human individuals and that only the moment of nidation can be considered as the starting point of this process then one must accept the responsibility of allowing early abortions and experimentation prior to the 14th day as acceptable. Defining the human person only in terms of relationships and of rational being can, if one doesn't talk about the soul and about our relationship with God, introduce the notion that perhaps people with mental disorders are questionable people. From the above examples one can readily understand that any deviation from the Churches teaching is of dire consequences.

The theory introduced by Karl Rahner by which God gives human parents the capacity to so transcend themselves that they create not only a body but a full human being - a body-soul complex does not answer any of the objections raised regarding the question human life - human person but replaces God as creator by parents (or doctors if the human being is conceived in a test tube). How one can use this theory in association with St. Thomas' theory of delayed animation is totally incomprehensible. All these contradictions leave one with the unpleasant thought that perhaps the only issue at stake and the only discussion is that of the age-old rebellion against God. But, all these contradictions vanish into thin air if one follows the constant and invariable teaching of the Catholic Church : Each and every human soul is directly and individually created by God.



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