Is an embryo a person?
In the familiar polemics on the subject of abortion one side argues in support of women's rights, the other in support of babies' rights. But so far only one side of the debate has attempted to engage a question that should be intrinsic to the abortion issue: What is the embryo?
To Dr. Jack Willke, president of the National Right to Life Committee, the embryo is a human being from the moment of conception. His definition of a human being depends upon the forty-six chromosomes first present in the fertilized egg. "Contained within the single cell who I once was," he says, "was the totality of everything I am today."
Judges and state legislators across the United States seem inclined to accept this argument about chromosomes and totality. In Webster v. Reproductive Health Services the Supreme Court upheld a Missouri fetal rights law that asserts "life begins at conception." In September a Tennessee court ruled that seven frozen embryos at the center of a bitter divorce suit are children, that they are "human beings existing as embryos." Judge W. Dale Young gave "custody" of the embryos to their "mother," and, basing his decision entirely upon the testimony of one geneticist, concluded that "a man is a man; that upon fertilization, the entire constitution of the man is clearly, unequivocally spelled-out, including arms, legs, nervous systems and the like; that upon inspection via DNA manipulation, one can see the life codes for each of these otherwise unobservable elements of the unique individual."
The "biological" argument that a human being is created at fertilization is increasingly used by antiabortion forces in their effort to back up religious arguments based on church tradition. This purportedly scientific argument comes as a surprise to most embryologists, however, for it contradicts all that they have learned in the past few decades. The benefit of that knowledge, more sophisticated, subtle and complete than ever before, has been notably missing from most public discussions of abortion and from all the legal decisions that have created so much recent publicity.
The embryo exists utterly beyond our normal means of understanding. We are accustomed to trust our eyes. A thing has bark around a thick column, limbs, branches and bunches of green leaves. It must be a tree. While the early embryo bears no physical resemblance to anything we think of as human, later, at three months, it has fingers, legs, a nose and eyes. But the first conclusions that one draws from even those appearances may have to be revised.
The fertilized egg knows nothing about how to make a finger, a nose or eyes. It knows only how to divide into two cells, which then know how to divide to make four. How, then, does the fertilized egg give rise to a baby?
The fertilized egg contains all the DNA necessary for the embryo to develop. Half the DNA has been supplied by the egg and the other half by a single sperm cell. We often read in textbooks and the press that this DNA is the "blueprint of life." But an analogy between a blueprint and the DNA is misleading. If a human being were a house, then the DNA would specify doorknobs, hinges, lumber and nails, window panes, wires, switches, fuses and a thousand other individual parts. But it would not tell how to put all those parts together in the right order and at the right time. It is unfortunate that biologists have contributed to the belief that DNA represents some sort of essence or "life force." Rather, it is only part of the information necessary for the correct formation of the embryo.
In fact there does not seem to be any blueprint for embryonic development. Each step toward greater complexity depends instead upon the pattern of cells and molecules just reached in the preceding step. The information required to make an eye or a finger does not exist in the fertilized egg. It exists in the positions and interactions of cells and molecules that will be formed only at a later time.
But if the individual does not arise out of the DNA then from where does he or she come? The fertilized egg clearly has potential. Perhaps if we consider the fertilized egg as a whole, poised as it seems to be to follow a preset pathway (blueprint or no), then we can discern the incipient individual.
We must ask, Is there a preset pathway? Is there only one road for the fertilized egg to travel? Embryologists have always been impressed by the ability of the embryo to adjust to alterations in its normal path of development. They have studied the embryos of fish, frogs, chickens and mice because these closely resemble human embryos. In fact, when early human and mouse embryos are compared, the process of development is so similar that these embryos are not distinguishable from each other in any significant way. Let us, therefore, consider one experiment.
If a fertilized mouse egg from two white-furred parents goes through four cell divisions, the embryo will have reached the sixteen-cell stage. If this embryo is then brought together with a sixteen-cell embryo from two black-furred parents, a ball of thirty-two cells is formed. This ball of cells will go on to make a single individual with mixed black and white fur: one mouse with four parents, two white and two black. Any particular cell of its body has come from either the one set of parents or the other. A similar event sometimes occurs naturally in humans when two sibling embryos combine into one. The resultant person may be completely normal.
If the two original embryos were determined to become particular individuals, such a thing could not happen. The embryos would recognize themselves to be different mice, or different people, and would not unite. But here the cells seem unaware of any distinction between themselves. They seem to recognize each other as early embryonic cells and nothing more. The only explanation is that the individual is not fixed or determined at this early stage. In fact the body pattern has not even begun to form.
The early human embryo, like the mouse, is a ball of cells. The body pattern of the embryo will be established only very gradually by these cells, and not in a way that one might intuitively expect. The fertilized egg does not divide into one cell destined to make the head, one to make an arm, another a leg. There is no program to specify the fate of each cell. Rather, a cell's behavior is influenced at each stage by its location within the developing body pattern of the embryo. Each stage brings new information, information that will change as the body pattern changes. And each cell will respond to this new information in a somewhat random way. For example, one cell of the sixteen-cell embryo may contribute randomly to the formation of many different organs or structures of the body. Later on a descendant of that cell may find itself restricted to the brain but will still be able to contribute to a wide variety of cell types there. It may make different types of nerve cells or non-nerve cells. And because of the extremely complex cell migrations that take place during the development of the brain, the cell's progeny may function in many regions of the brain.
With this layering of chance event upon chance event the embryo gradually evolves its form. The mixture of chance and planning that goes into every step of the process is what makes each person unique. Even the distinct pattern of ridges and swirls that make up a fingerprint is not preset in the fertilized egg. Identical twins grow from the same egg, have exactly the same DNA and develop in the same maternal environment, yet they have different fingerprints. If something so relatively simple and superficial as a fingerprint arises out of chance events, then what of an organ as complex as the human brain?
The fertilized egg is clearly not a prepackaged human being. There is no body plan, no blueprint, no tiny being pre-formed and waiting to unfold. It is not "complete" or "the totality" of a person. The fertilized egg may follow many different paths; the route will be penned in only as the paths are taken; the particular person that it might become is not yet there. Our genes give us a propensity for certain characteristics, but it is the enactment of the complex process of development that gives us our individual characteristics. So how can an embryo be a human being?
Of course, the embryo is always human; it is of human origin, but so is every egg and every sperm cell. The problem is in the definition of the word "human." It may be either an adjective or a noun. As an adjective it carries no particular moral weight. We have human hair, human fingernails; the human cells in our saliva all have forty-six chromosomes, but they have no special significance. The noun, however, does have a moral dimension. Its synonym "human being" connotes individuality or personhood. It may also be associated with human thoughts and feelings. With respect to the embryo, then, its use may relate to the development of the brain.
In the early embryo a structure forms that biologists call the neural tube. It is a hollow cord of cells that runs along the central axis of the body, complete from head to tail after the first month (human embryos have tails for a while). One end of this tube bulges like the far tip of a long thin balloon being inflated. This area is called the brain, although until the second month of development the cells there do not become nerves; there are no special connections among them and there can be no thoughts. During the third and fourth months, nerve cells appear. Simple reflexes form first. The largest and most complex area of the brain, the cerebrum, develops last of all. In its decision in the Webster case the Supreme Court majority took up the issue of "viability" -- the point at which the fetus can survive outside the womb -- and suggested that this stage might be reached as early as the twentieth week. Apart from the question of whether the lungs could function at this point, which in itself is doubtful, there is the more compelling matter of the brain, whose qualities ultimately distinguish us as human beings. In the cerebrum, the mature brain cell pattern is not seen until the sixth or seventh month.
The conscious mind is dauntingly complex, and its workings are just now beginning to be understood. We do know that the structure of the brain -- the types and locations of its nerve cells and their interconnections -- is intimately related to the function of the brain. The higher faculties must develop very late. Thoughts and feelings must arise very gradually. Thus, an embryo may have fingers, hands, a nose and eyes, even reflex movements, but still have no mind.
The early embryo, before the development of the mature human brain, has only one quality to distinguish it from all other living things: It has the potential to become a human being. But it is a strange kind of potential, having no determined path or blueprint to follow. The fertilized egg cell does not contain its fate, just as a grape seed does not contain wine.
Of course we know the potential of the fertilized egg and the early embryo because we have awareness, thoughts and feelings. But the early embryo has none of these things. This group of cells cannot know its fate or want to become anything. Still, each of us must struggle with the philosophical and moral implications of this type of potential. It may help to remember that potential here is very tenuous and dependent upon the influence of many extrinsic factors. And the very question of potential presents us with a "chicken or the egg" kind of problem. Every egg and every sperm cell in our bodies could contribute to the formation of a human being. Obviously, an egg or sperm cell is not a "complete" human being, but then neither is the fertilized egg. Fertilization, the injection of sperm DNA into the egg, is just one of the many small steps toward full human potential. It seems arbitrary to invest this biological event with any special moral significance. As we have seen, we are more than the sum of our chromosomes; DNA is not destiny.
There will always be arguments based on spiritual or ethical beliefs to convince an individual of the rightness or wrongness of abortion, but each person should first understand the biology to which those beliefs refer. State-imposed restrictions on abortion would clearly take away individual choice in the matter. But the state may not act on the basis of religious tradition. It must recognize the fundamental difference between an embryo and a human being. The nature of embryonic development makes it impossible to think of an egg or a cluster of cells as a person. Time itself must be woven into the fabric of the embryo before it becomes a baby. And most abortions in the United States are performed well before the pattern of the weave is recognizable. Ninety-one percent are performed within three months of fertilization. It would be a great tragedy if, in ignorance of the process that is the embryo, state legislators pass laws restricting individual freedom of choice and press them upon the people. The embryo is not a child. It is not a baby. It is not yet a human being.
Charles A. Gardner is conducting his doctoral research on the genetic control of brain development at the University of Michigan Medical School Department of Anatomy and Cell Biology. He is a member of the Ann Arbor Committee to Defend Abortion Rights.
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|Title Annotation:||science advisory|
|Author:||Gardner, Charles A.|
|Date:||Nov 13, 1989|
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