Tag Archives: fertilization

Can we know when life begins?

Dr. Patrick Lee says there’s a strong logical case for the pro-life position . . .

Dr. Patrick Lee

There is heated disagreement over abortion in our culture. But in the mainstream media the reasons for this disagreement are never discussed. A U.S. senator, for example, will be asked for his opinion, but he will never be asked why he opposes or favors abortion.

Apparently the reigning view is that people either abhor or approve of abortion merely through their emotions. Or perhaps it’s assumed that opposition to abortion is just a strange rule that some Christians happen to hold. In either case, the result is that no one discusses reasons pro or con because — it seems — there just aren’t any.

This is a mistake. There’s a strong logical case for the pro-life position. I will present some of the evidence that a human being begins at fertilization. If one adds to this point that every human organism is a person with basic rights (and there are strong arguments for this also), then the pro-life position has a robust logical defense.

To see this, let’s consider some of the facts about sexual reproduction. At fertilization a sperm unites with an ovum, each of them ceases to be, and a new entity is generated. (Hence it makes no sense to say that a sperm or an ovum becomes a mature human, or that a sperm or an ovum has the potential to become a mature human: Ingredients do not become what they enter into, whereas an immature human being — an embryo, fetus, or infant — does become an adult human being simply by maturing.) It’s obvious that the human embryo is a distinct entity, not a part of the mother or a part of the father. For unlike body cells, tissues, or organs, the embryo does not function as part of its mother.

The one-cell embryo (zygote) develops by dividing into two cells, then four, then eight and so on. While these divisions occur, all of the cells continue to be enclosed within a thin membrane called the zona pellucid, which is inherited from the ovum.

Are these merely a bundle of disparate cells? The evidence shows that together they make up one organism. These cells inter-communicate and seem to function together as parts of a whole in a regular and predictable manner. As a result, they perform an ordered, differentiated growth and constitute a stable body. For as the embryo travels down the uterine tube into the uterus during the first four or five days, the different cells begin differential gene expression (modifications of different parts of the DNA within the cells’ nuclei in order to generate different types of new cells that can function in different ways).

On day three or four, at the transition from the eight-cell stage to the 16-cell stage, the embryo differentiates into trophoblastic cells (precursors of the placenta) on the one hand, and inner cell mass cells (precursors of the permanent part of the embryo and fetus), on the other hand. This is the first overt functional differentiation that occurs, but the cells have been preparing for this differentiation since day one.

So from the zygote stage onward the cells are functioning as parts of a whole, and there is inner coordination toward the next step in a developmental trajectory that eventually involves a clear development of a body plan and distinct organs. The material constitution of the embryo from the one-cell stage onward provides it an active disposition to develop itself to the mature stage of a human being.

This is a new and distinct multi-cellular organism. It is developing itself in a predictable direction. Obviously it is also human since its cells have the genetic structure characteristic of humans.

The next question is crucial: Is this a whole human organism? This is important because human tissue and human cells alone are not whole human organisms — for example, an isolated skin cell or a heart before it’s implanted into a recipient. Each of these is human but neither is a whole organism.

The evidence indicating that the human embryo is a whole human is that it has within itself all of the internal resources and the active disposition to develop itself to the mature stage of a human being. The direction of its growth is internally coordinated — what it receives from outside itself is only a suitable environment and nutrition. The organizational information for its growth comes from within.

Moreover, at no stage after fertilization does there occur a fundamental change in the direction of growth. None of the changes that occur to this being afterward — as long as this being stays alive — qualify as producing a fundamental change in its interiorly directed growth, so as to involve the coming to be of a new organism. Rather, everything that happens after fertilization either assists or retards its interiorly directed self-development.

So a new, whole human organism comes to be at fertilization. And, given that we are human organisms, it follows that you and I came to be at the same time the human embryos that we once were came to be.

Patrick Lee, Ph.D., is the John N. and Jamie D. McAleer Professor of Bioethics and the director of the Institute of Bioethics at Franciscan University of Steubenville. He is a nationally known keynote speaker and author on contemporary ethics, especially on marriage and the value of human life.