Civil Engagement

Published Date: February 22, 2008 | Topics: Philosophy, Politics and Current Affairs

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Going another round on embryos.

[This article was co-authored by Robert P. George and Christopher Tollefsen.]

Will Saletan has posted a reply to our response to his review of our book Embryo: A Defense of Human Life. His efforts to shore up the points on which we criticized his review are, we believe, unavailing, but before identifying what strike us as grave defects in his argument, we wish to say a word about Saletan himself and why we appreciate this opportunity to engage him in debate. He is an intellectually honest and deeply morally serious man who genuinely aspires to get to the right answer on the vexed question of the moral status of the human embryo. He is unfailingly civil in engaging people with whom he disagrees, and he is, on any reckoning, one of the smartest and best informed journalists writing on bioethical issues.

In Embryo, we argued that the established facts of human embryology and early developmental biology make clear that the human embryo is no mere incidental mass of cells, but is a whole living member of the species Homo sapiens. The human embryo, in other words, is an embryonic human — a human individual in the embryonic stage of his or her development. (As Saletan acknowledges, in the human species sex is already determined in the embryo.)

Whether he or she was brought into existence by the union of gametes or by cloning, the human embryo is a distinct and complete (though, of course, dependent and developmentally immature) organism. Each of us began life as an embryo, and then developed by an internally directed process into the fetal, infant, child, and adolescent stages, and ultimately into adulthood, with his or her organismal distinctness, determinateness, and unity intact.

That is why it is true — and Saletan should, we believe, face up to this centrally important fact and its implications — that though none of us was ever a sperm cell or an ovum (or a somatic cell that was used in a cloning procedure), each of us was once an embryo, just as each of us was once an adolescent, a child, an infant, and a fetus. What each of us needed in the embryonic stage is what all living organisms, including human beings, need throughout their lives, namely, adequate nourishment and an environment that is suitable for the maintenance of health and well-being. In the embryo, these resources are provided by the mother, though in principle (and perhaps soon in practice) they could be supplied artificially.


Saletan challenges our argument on the scientific facts, and we are happy to engage him precisely there. He maintains that the biological status of human embryos is “messy” in ways that defy “neat categories.” Where we see distinct lines between embryos and ova, between embryos and their mothers, and between embryos and their twins, Saletan insists that there are “dotted” lines. Where we see a continuous identity between an embryo and the later human being, it is genetically and biologically continuous with, Saletan sees something murkier, two (or more) entities that “aren’t quite the same thing.” In consequence, Saletan denies that humans in the embryonic and fetal stages have dignity or value on a par with dignity and value of humans in later developmental stages, and he advocates a “moderate” set of policies governing IVF, stem-cell research, and abortion.

We would like to reiterate a point from Saletan’s own earlier review. The “moderate” policy is one that will result in an industry devoted to the mass production and destruction of embryonic humans. Moreover, it is a policy in which all citizens would be implicated, as their tax dollars would go to support the research, and as their doctors and hospitals would increasingly, and without concern, integrate the results of that research into the ordinary standard of care. For citizens who believe in the fundamental dignity and equality of human beings in all stages and conditions, the “moderate” policy is, in truth, a radical and frightening one.

In his reply, Saletan has usefully clarified his position on what a human embryo is. He acknowledges more than once that an embryo is a whole entity — a point we have stressed — but he claims that an embryo is simultaneously a “part (of the mother-child system) and a dyad (of potential twins or of embryo and placenta).”

Of course, both of us, Robert P. George (henceforth RPG) and Chris Tollefsen (henceforth CT) are also simultaneously parts and dyads. RPG teaches at Princeton — he is part of that university system. CT is married–he is part of a dyad of husband and wife. But no one, of course, would use these facts to challenge our claim to be single, determinate biological individuals. Being a part of a university (or country, or baseball team) does not effect a change in the nature or numerical identity of a human being; nor does being in a dyadic relationship such as marriage (or co-authorship).

These same points are true even if we add the feature of radical dependence to the mix, as Saletan does. A disabled member — a part, if you will — of a Himalayan mountain expedition depends upon the rest of the team to survive. Similarly, the breastfeeding infant depends upon the dyadic relationship with his or her mother not just to survive, but to grow and develop. Failure to receive the necessary nourishment, because of maternal abandonment, death, disease, or malnutrition, will stunt the baby’s growth, retard his or her development, and perhaps result in the child’s death. (It is of no consequence to the argument that a child could be rescued and provided with nourishment by another adult since, as we have noted, an embryo could be gestated in an artificial womb.)

But no one, we are sure, will doubt that the infant is a distinct human being. There is nothing murky here, however radically dependent upon the mother (and/or others) the child is for his or her life. The lines between the individual persons, no matter how dependent they may be upon each other, are solid, not dotted. These points suggest to us that the “logic behind viability as a standard of abortion jurisprudence,” which Saletan endorses, is in truth deeply flawed. It just does not follow that the less an “unborn human being relies on its mother, the more it encompasses its own developmental program, and the more we should treat it like a born child.” Born children, unborn children, embryonic children (as well as frail or disabled individuals who rely on others for support) — all stand or fall together by this criterion.

The deeper point here is that these kinds of part-whole and dyadic relationships presuppose the prior existence of living independent members of the human species. Human beings can, in some cases, voluntarily enter into relationships, and in other cases they enter life already in relationships, including biological relationships with parents. Without human beings, though, there are no universities, marriages, or parent-child relationships.

We see precisely the same sort of phenomena in the case of embryonic and fetal life. Although the embryo is a distinct organism and no mere maternal body part, successful implantation requires signals of receptivity from the mother. The embryo receives nutrition via the mother, and various choices she makes, such as eating well and resting, or drinking and smoking, will have consequences for the well-being of her developing child. It is true, then, that mother and child are in a relationship, and in a certain sense it makes sense to say that they form a “system.” But it is a relationship, as are those of which RPG and CT are a part, that presupposes two (and in some cases more) existing human beings; it does not create a human being out of some previously existing material that is “not quite” the same thing.

Eggs and sperm, by contrast, in their relationship to the wholes of which they are parts, and embryonic organs in their relationship to their corresponding wholes, are quite different. Gametes and organs are not what they are apart from the whole organisms of which they are parts. Rather, they are both formed by those organisms and intelligible because of their relationship to those organisms. A sperm cell, or a kidney, or even a hand, is functionally, and biologically, what it is because it is part of a larger whole. So, while being part of a “system” or “dyad” does nothing to call into question the individual identity of RGP, CT, or any embryo, the situation is different as regards RPG’s, CT’s, or any embryo’s parts.


Why, though, do we claim that this is what science shows? Isn’t it just a matter of interpretation whether A and B are two independently existing entities that work together, or whether they instead form some one thing, C?

Well, not all interpretations are equal — some are falsified by the evidence. Embryologists certainly see all the complexity that Saletan notes in the relationship between developing embryos of various species and their environments (including non-living environments). They also see, increasingly, the even more complex underpinnings of embryological development in the embryo itself. Maternal signaling is as nothing in terms of complexity to the vast array of developmental signaling internal to the embryo that triggers and guides every stage of its development and growth. An astonishing number of genes must be activated, at different times, and for different purposes, over the course of a developing organism’s life, to induce tissue development, morphogenesis, and other possibilities, and the mechanisms and pathways by which this is achieved are variegated and wonderfully complicated.

But contemporary works of human embryology do not point to anything in the working out of this development, or in the interactions of embryo and environment, or embryo and mother, that indicates either that a non-individuated cell structure later becomes an individual human being, or that some individuated but non-human being becomes a human being. Rather, as we note in our book, embryology text after embryology text identifies fertilization as the moment at which a new human individual comes to be. Stanford’s William Hurlbut accurately sums up the testimony of embryological science against the position Saletan embraces: “Fertilization initiates a distinct living being with an independent metabolic pattern, an intrinsic developmental program and an immanent finality. The biochemical processes that sustain and unfold the form of this being are in intricate and unbroken continuity, not dotted lines.”

And this is true of non-human species as well: As Scott F. Gilbert writes, in his book Developmental Biology, “When we consider a dog, for instance, we usually picture an adult. But the dog is a ‘dog’ from the moment of fertilization of a dog egg by a dog sperm. It remains a dog even as a senescent dying hound.”


These are somewhat general points, but the specific arguments raised by Saletan seem to us largely to be reiterations of his earlier objections. He raises four issues: (1) the role of maternally-derived factors, including maternal RNA, in an embryo’s growth and development, (2) the relationship between the embryo and placenta, (3) the phenomenon of twinning, and (4) the phenomenon of parthenogenesis. Saletan proffers each of these as justifying his claim that no clear distinction exists between the embryo and his or her mother, organs, twins, or precursor sex cells. Our general points should suffice to call into question this argumentative strategy, but we offer some further thoughts here on each of Saletan’s claims.

The embryo is radically dependent upon the mother in two different ways. First, and most obviously, the embryo lives in, receives nutrition from, and is in biological communication with the mother’s womb. Mother and embryo are engaged in a delicate relationship here, as we have pointed out above. And the relationship is mutual: Biologically, the woman is changed by the embryo.

Her body is now operating in a different way, suppressing some functions (menstruation, for example) and initiating others (production of milk, for example). The woman is different for being pregnant than she was before she was pregnant, and these differences would cease were the pregnancy to end. These facts do not call into question the independent existence of the mother. By the same token the impact of the mother upon her embryonic child casts no doubt on his or her status as a distinct individual organism.

The second way in which the embryo is dependent upon the mother is for its origins. Mother and father contribute sperm and egg, thereby also contributing a genetic inheritance, to the process of fertilization, without which there would be no embryo. Because fertilization brings together two haploid gametes of maternal and paternal origin, the embryo is genetically related to both parents. Yet no one would claim that the embryo’s genetic endowment — the genomic program which will serve as the embryo’s blueprint for growth and development — is not the embryo’s but rather belongs to the mother and father, or all three collectively. When the embryo comes into existence, the new genome is his or hers.

The same is true of the RNA found in the zygote’s cytoplasm. Crucial to the embryo’s development? Yes. Still a part of the mother? Certainly not. Saletan seems to have adopted something like the following line of reasoning: The RNA is in the egg, the egg is the mother’s, therefore the RNA in the fertilized egg is also the mother’s.

But this is fallacious. Indeed, if the argument were valid, then a similar logic would show that half the embryo’s DNA is also the mother’s. But the flaw in the argument is apparent: A “fertilized egg” is, in fact, no longer an egg, and hence no longer a part of the mother.

Evidence for this claim may be seen in the following. The role of eggs and sperm, in the biological economy of a mammal, is to unite. But after fertilization, the zona pellucida — the membrane that surrounds the egg — immediately hardens to prevent further sperm from entering. Although the single cell zygote looks, in many ways, like the egg that preceded it, it behaves now in a new and un-egglike way. And, as is clear, the fertilized “egg” is radically unlike the maternal oocyte in having a genetic endowment inherited from both mother and father.

The scientific evidence, then, indicates that although dependent in many ways upon the mother, the embryo is a biologically, genetically distinct individual, from its first moments oriented toward bringing about its own growth and development, and toward protecting itself from threats to that development, such as polyspermy.

Let us turn to Saletan’s remaining arguments.

First, the placenta. Saletan is impressed by the fact that something that we assert is a single individual organism, the embryo, generates two distinct structures — the embryo proper, and the placenta. This suggests to him that the early embryo and the later fetus “aren’t quite the same thing.” But our point is that the placenta is not a distinct structure, any more than your heart or lungs are: They are parts of you, and the placenta is a part of the fetus.

It is, admittedly, a large part; this is explained by the relatively small amount of nourishment contained in mammalian eggs (think, by contrast, of the large amount of yolk in the chicken egg you had for breakfast — all that protein would have been available for the embryonic chick’s nourishment). But the decisive, positive evidence showing that the placenta is a part of the embryo is that it is formed by the embryo, and is oriented toward the survival and flourishing of the embryo, not itself or any other organism.

Nor is the transitory nature of the placenta troubling. Like some other organs that function only over a defined period of the life span, this organ is discarded when its function is complete. Because a woman’s ovaries become atretic and “die” following menopause, does this mean they are not organs of the woman for much of her life? Is the “individuality” of a woman called into question because this portion of her body does not function for her whole life span? Of course not.

Next, twinning. Again, Saletan worries that the fact that one thing becomes two somehow jeopardizes the “oneness” of the original being. But how, exactly, is twinning a problem? Prior to splitting, an embryo is an individual; after splitting, there are two, one of which is perhaps the original, the other of which is new (or, what is less likely, the first goes out of existence and gives rise to two new embryos).

Similarly, prior to dividing a clump of day lilies, there is one plant, subsequently there are two. Prior to cutting a flat-worm in two with a razor blade, there is one worm, subsequently there are two. And prior to cell division, there is one bacterium, subsequently there are two. The fact that monozygotic twinning sometimes occurs in humans provides no evidence for supposing that human embryos are not (or are not yet) individuals. The plain fact is that they are.

Saletan himself saw this clearly enough in 2001 when he criticized those making the argument he has now embraced. He described the argument — “that since the early embryo could become one body or two bodies, maybe it’s nobody” — as the “thin logic of [a] lonely premise.” Nothing in the facts or logic of the case has altered since Saletan made that altogether accurate (and devastating) point.

And finally, parthenogenesis. Here, genetic identity between the original oocyte and the developing parthenote suggests to Saletan that the strict distinction between gamete and embryo cannot be maintained. But genetic identity between cell A and cell B — even when cell A is the source of cell B — is not sufficient for cells A and B to be the same cells. The zygotic Dolly the sheep was genetically the same as the skin cell whose nucleus provided Dolly’s genetic program. But Dolly was never that skin cell, for that cell behaved as a skin cell and would never, if implanted in a sheep womb, have grown and developed in the way appropriate to a sheep.

Nor will any oocyte, prior to the particular transformations brought about in parthenogenesis, grow and develop as a member of its species. In parthenogenesis, those changes to the oocyte do not require the assistance of sperm; nor, as in cloning, do they require external stimulus, such as an electric charge. Some species just have the capacity for parthenogenesis built into them (the human species does not appear to). But parthenogenesis is still a type of reproduction; it passes on the “generic” life of the species by allowing an individual member of that species to beget another individual which did not previously exist.


And this brings us to a final point. We continue to be puzzled by Saletan’s idealization of the “program” of humanity, and, seemingly, life itself: “You can’t isolate life’s program in one body, any more than you can isolate the Internet on one computer. Indeed, life is far more fluid than the Internet, with shared software that remakes its hardware as well as itself.”

But there is no Internet in the absence of individual computers, and there is no “program of life” apart from the particular individual living organic beings who are alive. Knowledge seeks the universal, but it is Platonic speculation, not scientific good sense, to elevate the universal to a higher metaphysical standing than the individuals who have concrete existence. Platonism of this sort is dangerous when it tempts us to suppose that particular individuals may legitimately be sacrificed in the name of an abstract “humanity” or “life itself.”

It would be a convenient fact, if indeed it were a fact, that human embryos are something other than living members of the human species — human beings — at the earliest developmental stage. We could, then, without qualms, and without implicating ourselves and our society in injustice or immorality of any kind, end unwanted pregnancies by abortion, and pursue every interesting or promising lines of embryo-destructive biomedical research. It is, in a far from trivial sense, in our self-interest, then, to be free to kill human embryos and even create human embryos to be killed in advancing our goals.

But self-interest can deflect sound judgment. History is replete with examples of self-interest blinding people to the humanity of others. Those whom we would exploit, or enslave, or kill, we first dehumanize. We notice all the ways that they are not “like us,” and overlook the profound respect in which, all of us are, “created equal.” Those who would justify or condone the killing of human embryos point to the many respects in which human beings in the early stages of development are not, or are “not quite” like us. Yet each of us was once just like them. And the being who was like them is precisely the same being — the same living member of the human species — who is now the adult.

That being, as he or she matured, became something very different in shape, size, feeling, consciousness, and the like not by a radical transformation that changed him or her from a non-human being into a human being, but by a gradual, gapless, and internally directed process by which he or she developed from the embryonic stage forward to adulthood. At no point in the process of development did any of us “become” a human being; rather the human being who was once in the embryonic stage of his or her life matured to the adult stage. needn’t look back in time for examples of the dehumanization of those who are “not like us.”

Human embryos are not alone among members of the human family who are today at risk of dehumanization. Those (and let us make clear that Will Saletan is most definitely not among them) who argue for the morality of euthanizing persons suffering from severe dementias or who are in minimally conscious states, or who would justify the killing of “defective” infants and severely retarded people, point to all the respects in which those whom they would kill are “not like us” — and some of these potential victims are, in certain respects, less like us than embryos. (Unlike embryos, they lack, in the words of philosopher Don Marquis, “a future like ours.”)

But just as we reject the idea that someone is less than fully human based on race, ethnicity, or sex, we should not condone dehumanization based on age, size, mental or physical capacity, stage of development, or condition of dependency. We should reject dehumanization tout court.

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