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If a Fetus Isn’t a Human Being, What Is It?

Michael Egnor
Photo credit: Kelly Sikkema via Unsplash. 

At the heart of the abortion debate are two sets of questions: scientific questions and moral questions. They are both important, and much of the rancor and division in the abortion debate stems, I think, from conflation of scientific and moral issues. They are not the same. Properly formed moral views depend on correct scientific understanding. If we don’t know what a fetus is, scientifically, we are hampered in making sound moral judgments about its protection. 

A recent post by biologist Jerry Coyne exemplifies this confusion. Coyne asks:

Where, I ask, is the evidence (beyond that asserted by religious authorities) that abortion is identical to murder, even in its very early stages? There is clearly a developmental continuum in a fetus, with an abrupt break when the baby is born, and so drawing a line for when a fetus becomes equivalent to a person with rights, including freedom from “murder”, is purely arbitrary. Many Catholics, though, draw the line at a rationally insupportable stage: fertilization.  A “person” is not created at fertilization: we have a zygote that now will go on to continue development. That zygote is an undifferentiated ball of cells without mentation or the ability to feel pain. And there’s no evidence it has a soul or anything differentiating it from the embryos of any number of vertebrate species.

Coyne profoundly misunderstands the biology of human development, and in doing so he reaches moral conclusions that even he — if he were to have a clear view of the science — would be hard-pressed to defend. How is it that a leading professor of biology could fundamentally misunderstand the biology of human development? 

Let Me Explain

Let us restrict our question about the nature of the fetus to the science of human development in the womb, which has been understood reasonably well since the mid 19th century. The question at issue is this: When does human life begin? Note that we are not asking moral questions or even metaphysical questions per se. We’re asking about biology: when, from a biological perspective, does an individual human being first exist?

We all agree that life begins at or after union of the sperm and egg. Fertilization marks the earliest moment in human development that human life might begin. Many other times after fertilization have been proposed — the first appearance of nervous tissue, or heartbeat, or brain waves, or quickening, or the ability to feel pain, or viability outside of the womb, or birth, or rationality, etc. At first, it seems a hopeless conundrum: there seem to be so many possible moments at which life begins that science is stymied. Perhaps science can’t tell us when life begins. But science most certainly can tell us, and does tell us. 

Every living cell or group of cells is either an individual member of a species or a part of an individual member of a species. There are no unclassified living things. And we all agree (tautologically) that whenever human life begins, each human life after that point is a member of the species Homo sapiens. But of course that entails a corresponding and critical question: What is the tissue (zygote, embryo, fetus, or neonate) before it is an individual human being?

The Critical Scientific Issue

So the critical scientific issue at the heart of the question “when does human life begin” is: What scientific description of the tissue (let’s call it the “fetus” for brevity) before human life begins makes sense biologically? Consider the options:

  1. The fetus is a part of the mother’s body.
  2. The fetus is not part of the mother’s body, but is an individual of another species.
  3. The fetus is not any kind of living thing — it’s just a clump of biological molecules undergoing chemical reactions. 

Consider the scientific implications of each option:

1) The fetus is a part of the mother’s body. if the fetus is a part of the mother’s body, then all pregnant women are chromosomal mosaics. That is, they are organisms that have two sets of genomes. Chromosome mosaicism is a rare disorder and is not synonymous with pregnancy. There is no such thing as “transient chromosomal mosaicism.” Furthermore, if the fetus is a part of the mother’s body, then half of pregnant women are hermaphrodites — i.e., they contain both male and female tissues. Needless to say, “transient gestational hermaphroditism” is not a recognized medical disorder. 

Furthermore, if a new human life begins by a piece of the mother’s body becoming a new organism, then human beings reproduce by buddingBudding is a form of asexual reproduction used by some species of worms, sponges, corals, and microorganisms, but it is not a means of human reproduction. 

There is no biological sense to be made of the claim that “the fetus is part of the mother’s body.” The claim leads to scientific implications that are nonsense. 

2) The fetus is not part of the mother’s body but is an individual of another species. If the fetus is an individual member of another species, then pregnancy is by far the most common parasitic disease among humans. What’s more, the transition in each pregnancy from a non-human parasite to a new human being is speciation — the evolution of a new species, “Homo fetus” to Homo sapiens — occurring with each pregnancy. This is, of course, scientific nonsense. 

3) The fetus is not any kind of living thing — it’s just a clump of biological molecules undergoing chemical reactions. If the fetus is not really living at all, then each pregnancy is a new origin-of-life event. This is also scientific nonsense. 

Clear and Straightforward Science 

So the biological answer to the question “When does human life begin?” is easy to answer from a scientific perspective: human life begins at the moment the sperm fertilizes the egg. This is not merely common sense and the claim of pro-life advocates, it is clear and straightforward science, as settled as heliocentrism and the existence of atoms. 

All cogent moral reasoning about abortion must begin with the understanding that human life begins at fertilization. There are no other scientific options. And here you can see where Coyne and other abortion proponents — even abortion proponents who are scientists — go awry. They don’t understand the simplest biological fact about human development — that human life begins at fertilization.  

So Coyne’s assertion…

A “person” is not created at fertilization: we have a zygote that now will go on to continue development. That zygote is an undifferentiated ball of cells without mentation or the ability to feel pain. And there’s no evidence it has a soul or anything differentiating it from the embryos of any number of vertebrate species.

…is nonsensical because it confuses scientific misunderstanding with moral reasoning. 

There is a simple scientific answer to the basic question at the heart of the abortion debate. Whatever a “person” is, a human zygote is most certainly a human being. 

The term “person” is a moral and legal category, not a scientific category, and it is a category open to moral discussion and debate. But “human being” is a scientific term, and it is not open to debate. The science is settled. Human life begins at fertilization, and cogent moral reasoning about abortion must begin with that scientific fact.