Beginning of Life: Fertilization and Ethical Issues


The process of beginning of a new life is still a mystery both for religious doctrines and for the modern scientific community. At the same time, advances in biology and genetics have shed light on the phenomena of conception, fertilization, and the development of the zygote and embryo, which later becomes a human being. Researchers have consistently described male and female functions in reproduction (Yanagimachi, 2017). However, these discoveries do not clearly address the question of the specific moment from which human life begins. This paper examines fertilization from a scientific point of view and, based on this data, analyzes the beginning of human life.

Relevant Concepts

It should be emphasized that sexual reproduction in the evolutionary sense was preceded by asexual reproduction, which is still widespread in unicellular organisms. It requires less energy and time and does not involve searching for a sexual partner, but it is not effective in avoiding harmful mutational changes or acquiring positive ones. Most cells in the human body reproduce in this way, for example, through mitosis or meiosis. Mitosis is an indirect cell division that implies the equal distribution of chromosomes between daughter nuclei, which ensures the formation of genetically identical daughter cells. Diploid cells are formed in this way, and they contain a complete set of chromosomes – one pair of each type. Meiosis, in turn, is the division of the nucleus of the eukaryotic cell with a decrease in the number of chromosomes in half (Yanagimachi, 2017). This leads to a transition from the diploid phase to the haploid one. Haploid cells, by contrast, contain only a single set of chromosomes.

Gametes are reproductive cells with a haploid set of chromosomes that participate in sexual reproduction. Human gametes are egg cells in women and sperms in men. Fertilization or syngamy is the process of fusion of different gametes, resulting in the formation of a diploid cell of the zygote (Miller & Pruss, 2017). The essence of this procedure is the recombination of genetic information between opposite-sex individuals of the same species. It should be noted that the zygote is the first stage of an embryo’s lifecycle. Over time, the zygote develops through mitosis and, when it enters the uterus, forms a blastocyst. The blastocyst consists of two cell populations: the embryoblast (inner cell mass) and the trophoblast, the outer layer of the cell. The trophoblast is involved in blastocyst’s attachment to the uterine wall, which is called implantation. Then, in the course of the gastrulation, complex transfers of the cellular material occur, and a part of it enters the previously single-layer embryo (Blastula) and lays out its wall, which thus becomes a double-layer (Gastrula). As the embryo becomes structurally more complex and more substantial during pregnancy, it turns into a fetus.

Fertilization Process

Thus, fertilization consistently results in the transformation of two opposite sex gametes into a single human fetus. After natural intercourse, the sperm reaches the egg cell and penetrates it through the membrane. According to Zielinska and Schuh (2018), “once the egg and the sperm have fused, the parental chromosomes need to be united” (p. 128). The zygote that moves towards the uterus develops through mitotic division. This process is more appropriate to refer to as cleavage, since the total size of the embryo does not increase, and with each subsequent division, the daughter cells become smaller.

After some time, these cells form the previously mentioned cell groups: embryoblast and trophoblast, and the zygote itself turns into a blastocyst. The next stage of embryo development is implantation, through which it receives the necessary oxygen and nutrition. These resources provide the embryo with the opportunity to become even more complex during the gastrulation, when different germ layers are separated: the ectoderm, the entoderm, and the mesoderm. These germ layers become the source of all human tissues and organs. They give rise to the necessary differentiation of various elements of the human organism, which eventually leads to the transformation of the embryo into the fetus.

Human Life Beginning

The resolution of many ethical issues, such as abortion, depends on determining when human life begins. In accordance with conventional perceptions, “human organisms begin to exist at fertilization” (Miller & Pruss, 2017). This position is accepted by many researchers and ordinary people, as it implies that a new human life begins at the moment of combining the genes of both parents into one cell. At the same time, this point does not give high accuracy and is subject to particular criticism.

Researchers are arguing about which particular stage of fertilization can be considered the beginning of life. Zielinska and Schuh (2018) have revealed that the parental genomes remain isolated, staying inside the zygote for some time, even during the first embryo division. Accordingly, it is difficult to state unambiguously whether the zygote, which has not yet merged parental chromosomes, is a new individual organism. Moreover, this concept has been criticized for its contradiction with the scientific ideological paradigm. Paulson (2017) states that the idea of “‘human life’ implies individuality, which is not consistent with scientific observations” (p. 566). According to the author, the egg and sperm are the same living organisms as the zygote (Paulson, 2017). Therefore, there is no reason to speculate about the emergence of a new individual biological life at the moment of fertilization. Thus, there are several views on the beginning of a new life, and discussions among their proponents are continuing.

ERD Part Four Introduction Summary

The Catholic Church regards human divinity as the basis for ideological protection of the sanctity of human life. According to the Ethical and religious directives for Catholic health care services (ERD, 2009), “the Church’s defense of life encompasses the unborn and the care of women and their children during and after pregnancy” (p. 23). It proclaims the significance of the act of marriage and love that unites husband and wife and gives birth to a new life. Moreover, this life is considered sacred “from the moment of conception until death” (ERD, 2009, p. 23). Thus, the Church also defines fertilization as the moment of the beginning of a new life.

The Church believes that the birth and education of children is the greatest gift of marriage that contributes to the welfare of parents. According to ERD (2009), the Church cannot accept contraceptive measures that prevent or terminate pregnancies. Furthermore, it considers artificial insemination methods and other reproductive technologies as unnatural and contrary to “the holy laws of God” (ERD, 2009, p. 24). Thus, the Church has a conservative position regarding the beginning of human life and the intervention of science in this sphere.


The fertilization process is still being studied by biologists and geneticists, despite the fact that scientists have already identified the main stages and regularities of embryo development. Although there is detailed research data in this regard, the issue of the beginning of a new life is still controversial and unresolved. There are many advocates for the position that fertilization is the moment when human life starts, and it is supported by the Church, although many scholars are criticizing this thesis.


  1. Miller, C., & Pruss, A. (2017). Human organisms begin to exist at fertilization. Bioethics, 31(7), 534-542.
  2. Paulson, R. J. (2017). The unscientific nature of the concept that “human life begins at fertilization,” and why it matters. Fertility and Sterility, 107(3), 566-567.
  3. Yanagimachi, R. (2017). The sperm cell: production, maturation, fertilization, regeneration. Cambridge University Press.
  4. Zielinska, A. P., & Schuh, M. (2018). Double trouble at the beginning of life. Science, 361(6398), 128-129.
  5. United States Conference of Catholic Bishops. (2009). Ethical and religious directives for Catholic health care services. Web.

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NursingBird. 2022. "Beginning of Life: Fertilization and Ethical Issues." January 23, 2022.

1. NursingBird. "Beginning of Life: Fertilization and Ethical Issues." January 23, 2022.


NursingBird. "Beginning of Life: Fertilization and Ethical Issues." January 23, 2022.