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