On the Status of the Human Embryo

The above considerations and statements about the concept of the person would seem to bring us to the conclusion that the human embryo should be considered a human being in all respects, and therefore a person, from the moment of fertiliza­tion.

Agazzi clearly presents the problem of the identification of the moment of indi­vidualization of the human embryo when he presents the works and the document of the Italian National Committee for Bioethics on the theme: “Identity and Status of the Human Embryo” (1996; Agazzi 2005).

He explains how they came to the unanimous conclusion that the human embryo is a person from the moment in which it is a human individual; but he also shows that there were many difficulties with regard to the status of individual in the first two weeks of development: the characteristic of totipotentiality of its cells, the possibility of twinning, the lack of the primitive streak.

In another text he elaborates on this position of “perplexity,” arriving at the conclusion that the human embryo is not a human individual during the first two weeks of its initial development (Agazzi 2007).

It is above all the possibility of the phenomenon of twinning and the formation of “chimeras” (the fusion of the cells of two embryos into a single one) that bring Agazzi to his position:

[...] It is difficult to understand how a human individual can develop, dividing his indi­viduality into two or more individuals or, symmetrically, how two different human indi­viduals can be compacted into a single individual. This difficulty would disappear if we admit that during the period under consideration, the individual entities gradually formed are only cell systems that can lead to different results [.] (ibid.).

The key point is that of the individual identity that we can better grasp through the criterion of re-identification: the recognition of the same individual despite being in different circumstances and conditions. Proposing the thought experiment of twins that return to the past progressively in their minds, each of them could say, “It was me,” but only up to the point at which they were established as two sepa­rate individuals: “[...] because the individual entity existing before that time gave rise to his embryo as well as that of his twin brother and, for this reason, s/he can say, ‘It was me’” (ibid.).

The Author proposes, therefore, the solution of accepting the term (and reality) of the so-called pre-embryo: a “biological structure” resulting from fertilization that will give rise to the embryo around the fifteenth day of development.

In this way, he concludes: “The human embryo is a full individual (or person), but this ontological state can not be attributed to human pre-embryo.”

I have summarized Agazzi’s explanation in a fairly detailed way, as, to me, this seems to be a key point in bioethics today. For the same reason I will now make some critical considerations.

First of all, it must be noted that the term “pre-embryo,” actually used in cer­tain bioethical and scientific documents, has been “disgraced” for several years now, especially in the scientific field. Among the various possible quotes or tes­timonials, I recall here only that of R.O’Rahilly. It’s especially interesting if you keep in mind that O’Rahilly is the embryologist who established the “Carnegie Stages of Human Embryological Development”, used for many decades now by the International Nomina Embryological (now the Terminologica Embryologica) Committee which determines the scientifically correct terms to be used in human embryology around the world.

In the third edition of his textbook Human Embryology & Teratology (O’Rahilly and Muller 2001), he gives five reasons why it is not appropriate to use the term “pre-embryo”; one of them is simply that “it may convey the erroneous idea that a new human organism is formed at only some considerable time after fertilization” (O’Rahilly and Muller 2001).

From the philosophical point of view, it seems to me that the concept of sys­tem can illuminate the issue of the individualization of the embryo. I am a person because I am a human individual; and I am an individual because my body is a bunch of cells which are structured into a whole, which is a living, organic system. Since when am I an organic system structured as a whole? Embryology shows me that it’s from the time of fertilization of that oocyte by that spermatozoon. In that moment, a “biological structure” is formed, which is a real living organism, a liv­ing organism of the human species.

Let us do another thought experiment. Imagine we pull out the four morula cells contained within the zona pellucida at a certain time. We replace those cells with four amoebae. Suppose that the amoebae could multiply as embryo cells can. We know, however, that those amoebae will never form, as the cells of the embryo do, the various biological structures of what we call a blastocyst (about five days after fertilization), with the embryoblast and the trophoblast, with the cells already differentiated into “polar” and “non-polar”, leaving a large empty space in the center, etc. The amoebae would not do what the embryonic cells do because they would be merely an unformed cluster of cells, while the embryo is indeed a cluster of cells, but it is organically structured in a organic living system.

In 2001, a team in Cambridge led by K. Piotrowska demonstrated experimen­tally that at the very moment of the penetration of the spermatozoon into the oocyte, a morphological axis is established, from which the cells of the embryo multiply and differentiate in a precise systematic order (Piotrowska et al. 2001; Piotrowska and Zernicka-Goetz 2001).

Certainly, we must take the phenomena that Agazzi and others suggest seri­ously, that is that we cannot speak of individual identity in the earliest stages of embryo development, especially regarding the phenomenon of monozygotic twin­ning (and the possible formation of a chimera).

In my opinion, though, none of the reasons given, nor all of them together, demonstrate that the embryo is not an individual from the moment of conception. I will speak here only on twinning.

It is true that we do not know well the causes and mechanisms of monozygotic twinning, but we can say that it is due to the separation of some cells, which, still being totipotent, can generate a second individual, genetically identical to the first. Certainly we know that this can be caused artificially, as is frequently done with animal embryos from the fifties, with the technique of splitting. It has being also done with human embryos, in the famous experiment by Hall et al., at the George Washington University School of Medicine in 1993 (cf. Gourdon and Byrne 2002).

Actually, reproduction by twinning or by gemmation is very frequent in many species. In the case of many plants and some animals, you can separate one part of the organism from which a second plant or animal derives. This happens with the rose plant, the willow, and with some annelids (in a natural way, by binary fis­sion, or even after forced cutting, for example in the case of some species of earth­worms). If a branch of a rose plant generates a second plant, should I conclude that the original plant was not a living individual? Is this earthworm, from which a part comes off generating a second earthworm, not a living individual?

Human twinning can be considered a type of reproduction by fission. Perhaps thinking that a human being can derive from the body of another has a slightly odd emotional effect on us, but I do not see why we cannot understand it rationally.

Let’s take the abovementioned thought experiment proposed by Agazzi again. I think that if I were a monozygotic twin, going back in time in my mind I would say, “It was me.” Since the beginning of my existence, I have been the same living organism that I am now, with this size and these characteristics; I do not know if it was originated by the fertilization of an oocyte by a spermatozoon or after the separation of a part of the body of my twin brother; but that human living organic system “was me”.

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