Agency, Pregnancy and Persons

Essays in Defense of Human Life

Nicholas Colgrove, Bruce P. Blackshaw, Daniel Rodger, Nicholas Colgrove, Bruce P. Blackshaw, Daniel Rodger

• Publisher: Routledge
• Year: 2022
• ISBN:
  9781000622904
• Edition: 1
• Topic: Philosophie
• Subtopic: Ethik & Moralphilosophie

This book provides extensive and critical engagement with some of the most recent and compelling arguments favoring abortion choice. It features original essays from leading and emerging philosophers, bioethicists and medical professionals that present philosophically sophisticated and novel arguments against abortion choice.

The chapters in this book are divided into three thematic sections. The first set of essays focuses primarily on unborn human individuals—zygotes, embryos and fetuses. In these chapters, it is argued, for example, that human organisms begin to exist at conception and that zygotes, embryos and fetuses are persons. These chapters also explore questions about whether or not zygotes, embryos and fetuses are part of their mothers' bodies. The second set of essays focuses primarily on elective abortion and the debates surrounding it. These chapters consider whether or not opponents of abortion are commonly hypocritical, how opponents of abortion should think about adoption, how emerging technologies may affect the current debate and whether or not those participating in the debate should rely on analogies to support their case. Finally, the third set of essays shifts focus from the legal and moral status of elective abortion to its place in medical practice. In these chapters, it is argued that elective abortion embodies a kind of ableism, that elective abortion is medically unnecessary, harmful to women's mental health and that telemedicine abortion poses significant risks to women's health.

Agency, Pregnancy and Persons offers an up-to-date examination of unborn human beings, the debates surrounding elective abortion and the place of elective abortion within medical practice. It will be of interest to medical professionals and those who work in philosophy, bioethics and medical ethics alike.

Part I Zygotes, Embryos and Fetuses

1 Is the Human Embryo an Organism?

Maureen L. Condic

DOI: 10.4324/9781003181576-3

1 Introduction

Prior to the application of medical ultrasound to the field of obstetrics in the late 1950s (Donald et al. 1958), human prenatal development was largely inaccessible to direct observation. Consequently, while scientists, philosophers and bioethicists have considered the origins of human life for a long time (for example, Aristotle discusses embryonic development extensively in De Generatione Animalium), the conclusions they have drawn were based on very little factual evidence, and appealing to historical experts or to religious traditions yields a plethora of contradictory opinions.¹

Yet this apparent lack of historical consensus does not reflect the modern scientific evidence or the views of modern scientists. An informal review of commonly used medical textbooks and the peer-reviewed scientific literature (Condic 2021) reveals numerous assertions made by research scientists that life begins at the fusion of sperm and egg to form a one-cell embryo or zygote—e.g., “A new life begins with the unification of the maternal and paternal chromosomes upon fertilization” (Scheffler et al. 2021) and, “The formation of zygote is the beginning of mammalian life” (Meng et al. 2020).

These statements are significant, not necessarily because the papers in which they appear provide scientific evidence for the conclusion that life begins at sperm-egg fusion (although some do provide such evidence), but rather because the statements have been published in peer-reviewed scientific journals without citation or explanation, which indicates that they are seen as uncontroversial matters of accepted fact by the scientific community. Had any of the authors (often a large number; 23 authors contributed to the two aforementioned examples), the peer-reviewers (typically three for each paper) or the editors of the journals (often research scientists themselves) objected that such statements were unsupported or controversial, they would have been either qualified or removed prior to publication.

Recent sociological research also suggests that there is a strong consensus among scientists on the question of when human life begins. A survey exploring the views of over 5,000 biologists from more than 1,000 institutions around the world demonstrates remarkable agreement on this topic. In each of the four measures employed, there is strong consensus (75%–91%) that human life begins at fertilization. In an overall combined measure, 95% of academic biologists affirm this view, irrespective of their political party affiliation or their views on abortion (Jacobs 2018, 2019).

The fact that there is such a clear consensus within the scientific community on the question of when human life begins stands in contrast to the wide range of views held by citizens. A recent national poll indicates that 38% of registered voters in the United States think life begins at conception, 15% at viability, 16% at birth, with the remainder unsure or citing other events (MaristPoll 2019). Given the diversity of opinion on this question in the eyes of the public, what is the scientific basis of the strong consensus of biologists? To address this question, early human development is briefly outlined, followed by a presentation of the evidence supporting the conclusion that human life begins at sperm-egg fusion and ending with a brief discussion of common objections to this conclusion.

2 Early Human Development

Early human development is summarized in Figure 1.1. Briefly, upon sperm-egg fusion at fertilization, a single cell (the zygote) is formed (Figure 1.1A). The zygote divides rapidly, producing a number of smaller cells known as blastomeres (Figure 1.1B). By the second or third day following sperm-egg fusion, the blastomeres have formed a ball-like structure known as a morula-stage embryo (Figure 1.1C). Cell division continues, and by the fifth day, the embryo has grown to about one hundred cells and formed a fluid-filled structure known as a blastocyst (Figure 1.1E). At this stage, the first two committed cell types have arisen. The cells that make up the outer layer of the blastocyst are known as trophectoderm (TE). Inside the blastocyst is a cluster of cells, known as the inner cell mass (ICM).

Figure 1.1 Early human development. (A) The one-cell embryo or zygote forms at sperm-egg fusion. Early development occurs within an acellular protein coat known as the zona pellucida (gray circle). (B) The zygote divides to form the two-cell embryo at 24–30 hours. Individual cells are known as blastomeres. Substantial evidence indicates the first two cells are distinct on a molecular level (i.e., “specified” to assume different developmental paths). (C) The morula, or eight-cell embryo, forms on days 2–3. (D) On days 3–4, cells begin to adhere more tightly to each other, forming the early blastocyst, which fills with fluid and gives rise to the first two committed cell types at the 32-cell stage. After this stage, cells are unable to change their developmental fate in response to new signals. The outer cells (dark gray) are trophectoderm (TE). The inner cells (light gray) are inner cell mass (ICM). (E) Cell division continues, and implantation occurs at the expanded blastocyst stage (days 5–6) when the inner cell mass (ICM) has divided into epiblast (light gray) and hypoblast (white). (F) The postnatal body of the fetus (not shown to scale) is formed largely from ICM, while the placenta and membranes are largely derived from TE. This figure has been adapted from an earlier version published in Condic, M. L. (2020). Untangling Twinning; Identity; Totipotency and the Value of Human Embryos. University of Notre Dame Press. Notre Dame, IN.

3 How Do Scientists Determine When a New Cell Type Has Formed?

As a sexually reproducing species, individual humans arise from the fusion of two distinct gamete cells (e.g., a sperm cell from a male and an egg cell from a female). Logically, no new human cell or human individual can exist so long as the gametes persist. Yet the product of sperm-egg fusion is sometimes referred to as a modified gamete (for example, a “fertilized egg” or “penetrated oocyte”),² terms that suggest the female gamete persists following sperm-egg fusion. Yet is this a scientifically accurate description of the product of sperm-egg fusion? In considering the scientific evidence relevant to the question of when human life begins, we must first address the more fundamental question of when the gametes cease to exist and when a new cell, distinct from sperm and egg cells, comes into existence.

The scientific basis for distinguishing when a new cell arises, either in the laboratory or as a consequence of a natural biologic process, rests on two relatively simple criteria: differences in molecular composition and differences in behavior (For example, see Wagner and Klein 2020; Xia and Yanai 2019). Quite often, these two changes will occur together; when the molecules present in a cell change, the behavior the cell exhibits will also change because new molecules will mediate new kinds of cellular activities.

Yet cells of a single type can naturally exist in more than one state, with molecular/behavioral changes occurring either in response to an external signal (such as a hormone) or as a consequence of a natural physiologic process (such as cell division). How do scientists distinguish between such “house-keeping” alterations in cell state and changes that signal the onset of a new cell type?

Molecular changes occurring within a single cell of a specific type are cyclical, with the cell returning to its initial state over time. In contrast, when a new cell type is formed, the cell enters into a novel trajectory that proceeds only in a single direction—i.e., the cell will initiate a new pattern of behavior that is not observed in the cell type (or types) that gave rise to it and will not return to the prior molecular state of the precursor cell(s).

A second situation in which a change in molecular composition and/or behavior does not signal the formation of a new cell type is the process of cell-type-specific maturation (Marioni and Arendt 2017). Both during development and ongoing replacement of tissues within the body, cells frequently arise in an immature state and must undergo “differentiation” to assume their mature function. Such immature cells are distinct from the precursors that gave rise to them, as evidenced by the initiation of a new pattern of behavior and gene expression that routinely culminates in a specific mature cellular phenotype. Yet the changes that occur within a single cell during this trajectory of maturation do not signal a continuous alteration in cell type, any more so than the changes that occur during maturation of an individual human being from childhood to adulthood represent a continuous progression of distinct “persons”. Rather, they constitute a cell-type-specific maturational sequence—i.e., a series of predictable molecular, structural and functional changes that proceed in only a single direction.

Distinguishing between cyclic changes, cell-type-specific maturational changes and changes that signal the initiation of a new cell type requires observation over time, yet these three classes of alterations can be reliably segregated from each other, based on objective evidence. Using the previously noted criteria, an international consortium is currently collecting single-cell transcriptomic, epigenomic and imaging data both to determine how many human cell types exist and to distinguish between changes in cell type and cyclic changes in cell state (Regev et al. 2017).

4 When Does a New Cell Type Arise during the Interaction of Sperm and Egg?

Based on these criteria, the fusion of sperm and egg clearly produces a new cell. Cell fusion is a rapid event (Bianchi and Wright 2016; Whitlock and Chernomordik 2021) that establishes a well-defined “moment” at which sperm and egg cells give rise to a single hybrid cell, most commonly referred to as the zygote or one-cell embryo.³ Following the binding of sperm and egg (Jiménez-Movilla et al. 2021), the membranes of these two cells fuse, creating a unified cell surface and a unified intracellular compartment (Satouh et al. 2012). All of the lipid and protein components that were previously associated with the sperm cell are incorporated into the newly formed zygotic membrane, and the intracellular contents of the sperm are incorporated into the intracellular cytoplasmic milieu, changing the composition of both cellular compartments.

In addition to these molecular changes the DNA of the zygote is also unique. During gamete formation, DNA recombination (Sanchez et al. 2021) and parent-specific DNA modifications known as genomic imprinting (Hanna and Kelsey 2021) cause the genome/epigenome of the zygote to be distinct from either of the parental genomes.

Because the zygote contains all the components of both sperm and egg, it has a unique molecular composition that is distinct from either gamete and thus satisfies one of the two scientific criteria for establishing that a new cell type has been formed.

Subsequent to sperm-egg fusion, a large number of events are rapidly initiated within the zygote (some within minutes) that do not normally occur in either sperm or egg,⁴ demonstrating that the newly formed cell immediately assumes a novel pattern of molecular behavior that is distinct from the behavior of gametes. These changes are not cyclic (i.e., over time, the zygote does not return to a molecular and behavioral state characteristic of either a sperm cell or an egg cell). Rather, the human zygote initiates a novel molecular trajectory and novel pattern of behavior, thus satisfying the second criteria for the formation of a new cell type.

Based on this factual description of the events following sperm-egg fusion, we can unambiguously conclude that a new cell (the zygote) with a new pattern of behavior, a novel molecular composition, a unique genome and a unique epigenetic state comes into existence at the scientifically well-defined “moment” of sperm-egg fusion.

5 How Do Scientists Distinguish between a Human Cell and a Human Being?

The scientific evidence clearly establishes that sperm-egg fusion does not generate a modified gamete (e.g., an erroneously termed “fertilized egg”), but rather produces a new cell that is distinct from either sperm o...