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The Machine of a New SoulThe messy biology of human embryos.

By William Saletan
Updated Wednesday, Feb. 13, 2008, at 9:16 AM ET
Linda Hamilton. Click image to expand.

Are embryos morally equal to people? I say no. Robert George, a member of President Bush's bioethics council, and his colleague Christopher Tollefsen say yes. In their new book, Embryo: A Defense of Human Life, George and Tollefsen conclude not only that embryo-destructive stem-cell research should be defunded but that any research involving embryos should be banned if it even slightly risks an embryo's health. They propose to halt the common practice of producing extra embryos during in vitro fertilization and to require that every IVF embryo be transferred to a womb.

In Sunday's New York Times, I reviewed the book's arguments. A day later, the authors replied on National Review Online. This is a conversation worth pursuing. George and Tollefsen are pushing the discussion into an area—embryology—where, in contrast to the usual shrieking about abortion, real progress can be made. They're civil, logical, and smart. I've seen George pick apart fuzzy-thinking adversaries at meetings of the bioethics council. It's like watching a cat with mice. Today, unfortunately, I'll be the mouse.

The virtue of Embryo is that the authors stake their case on science and logic, not religion. What makes you a human being, they argue, isn't a soul, but "a developmental program (including both its DNA and epigenetic factors) oriented toward developing a brain and central nervous system." They believe that this program starts at conception and therefore, so does personhood.

I like this bet on science. It's scrupulous, brave, and constructive. Let's toss in our chips and call the bet. We'll have to accept what science shows: Conception is, as George and Tollefsen argue, the sharpest line we could draw to mark the onset of moral worth. But they, in turn, will have to accept the other side of what science shows: The lines of embryology are dotted, not solid. Such lines don't warrant severe categorical restrictions on stem-cell research or assisted reproduction.

Start with the line between embryo and mother. They send signals back and forth to facilitate the embryo's migration, implantation, and nutrition. The embryo carries the mother's RNA, which directs its growth. What's more, the embryo is already on her way toward motherhood, with primordial germ cells up and running in her second week of development. The same program that created her is creating her children. It will kill her, and later them, revising not just individuals but families and species. 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.

George and Tollefsen assume a clear distinction between wholes and parts. Eggs and sperm are parts, they reason, while an embryo is a whole. At conception, the parts become a whole, the program launches, and personhood begins. But it isn't that simple. Some embryos divide after conception to become two or more people. Are those embryos, prior to twinning, an individual? Furthermore, all of us came from embryos that were part "embryoblast" (the segment that became a person) and part "trophoblast" (the segment that became placenta). The placental lineage grew you to birth, separated, and died. In computer terms, it's like a Zip file. In human terms, it's a bit like a mother. In these ways, the early embryo is simultaneously a whole, a part (of the mother-child system), and a dyad (of potential twins or of embryo and placenta).

The egg-embryo distinction, too, is permeable. George and Tollefsen write that eggs must combine with sperm or die. They say an organism "was never itself a sperm cell or an ovum." But look what just happened at a zoo in Kansas: another case of parthenogenesis—eggs becoming offspring without fertilization. This process has produced adults in dozens of vertebrate species, including sharks and turkeys.

And those are just nature's tricks. With biotechnology, we're adding our own. Through IVF, we've separated, for the first time, internal and external elements of the embryonic program. Through cloning, we've turned adult cells into embryos. Through viral injections, we've turned adult cells into embryonic stem cells. Through aggregation, we've made embryonic mouse stem cells grow into mice. By tweaking a single gene, we're learning to alter embryogenesis so that what would otherwise become an embryo becomes instead a disorganized bunch of stem cells.

In their rebuttal, George and Tollefsen try to sharpen these blurred lines. "The embryo is not a maternal body part," they observe. That's true, but it misses the point. The problem isn't that they put the embryo in the wrong category. It's that the embryo defies such neat categories. It's a part, a whole, and a dyad.

Maternal factors don't alter the embryo's genetic humanity, the authors write; they "merely enable it to continue to grow and develop." True again. But the embryo's dependence on these factors for its very life makes them more central to the embryonic program, not less. Indeed, this is the logic behind viability as a standard of abortion jurisprudence: The less the unborn human relies on its mother, the more it encompasses its own developmental program, and the more we should treat it like a born child.

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William Saletan is Slate's national correspondent and author of Bearing Right: How Conservatives Won the Abortion War.
Photograph of Linda Hamilton by Getty Images.
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Remarks from the Fray:

This discussion underlines a common tactic of the in the abortion debate: one side asserting that their beliefs are scientifically confirmed, that they are merely making a scientific claim when, in fact, they are making a moral or philosophical claim. "Science tells us that life beings at x", therefore, the speaker's beliefs are sacrosanct. But it always ends up as another disputable belief claim. People try to leverage their opinions with the supposed irrefutability of science; but the consequences of any scientific claim is a matter of philosophy.

Is the fact of a developmental program that is oriented towards developing a brain and central nervous system something that can be scientifically, experimentally tested? Yes. Is the belief that this program begins at conception something that can be scientifically, experimentally tested? Yes. Does science assert any particular moral consequences from those facts? No! "[A]nd therefore, so does personhood" is a claim that has no scientific value; it is a purely philosophical claim. Like any other disagreement about abortion-- or any other moral or ethical dispute-- we are left merely with competing philosophical claims, and, as usual, one side claiming that "it is perfectly obvious that...." These two researchers are no different from any one else engaging in the abortion debate, save that they are trying the worn out tactic of asserting that their position has the "certainty of science."

Science cannot solve our moral disputes. I'm sorry. There is no Ten Commandments hidden in our DNA, no "fundamental, real morality" to be deduced from a GUT. Those who claim otherwise are either arguing in bad faith, as these two are, or are simply unable to deal with the fact that we will always be trapped in the muddle.

--Freddie

(To reply, click here.)

Mr. Saletan, you admit that embryo formation, although dotted, is the sharpest line we can draw in human development. If that is so, then from an ethical standpoint, shouldn't it also be the point at which we make the distinction between human and non-human? Although imperfect, it is the clearest distinction that we can make based on what we know. To infer whether one is human at any point later in development would seem to me to be totally irresponsible. It's like saying because there is no definitive line, any arbitrary point in development would do just as fine. If you accept that reasoning then how can we defend ending the life of a fetus just prior to birth but not right after?

If science provides us with new facts that move the line either forward or backward in development then so be it. But given what we know, I think it is our ethical responsibility to make a decision based on the evidence we have. If I follow your logic to its end, then I don't see any reason why it wouldn't be morally wrong for me to end the life of anyone over the age of 0 days.

--UserName

(To reply, click here.)

So, yes, the columnist has a great point, a very large point, to make: biology is pretty complex and generally makes it impossible to draw neat clean lines without any ambiguity when you spend your time looking at the details. Scale matters, and emergence helps us draw lines, but only when we gaze at the appropriate scale. In the end, looking at smaller and smaller scales, emergence decoheres and identity breaks up. Not only the identity of individuals, but groups and all sorts of patterns. Without identity, there is nothing to discuss, analyze, protect or care about.

This is the problem that makes it almost impossible, if not wholly impossible, to define species, communities, individuals, alive, dead, ecosystems, and all other manner of biological entities we would like to define.

I can take any definition you give for these things and turn them on their head to the point that the original word is utterly useless. Amazing what a PhD in biology can do for ones ability to define things. I can make bacteria part of the person, an entire hive of bees a single organism, the beach part of the ocean and define away all those endangered 'species' you care so much about.

This is about as helpful as the scholastic games the collegians in Canterbury Tales are accused of, however. This sort of definitional argument has merit only when it helps us clarify function, form, predictive capacity, and moral weight. We need science to help us understand what we are doing, what we can do, what will happen when we do something, and what we should do - not to tell us that all our words are meaningless. English departments do that just fine.

In the end, objecting that the biology is messy is not a helpful argument - because plenty of conservative and liberal and otherwise political, moral, ethical and rhetorical positions rest on similarly drawn lines in the biology. Undrawing all the lines is a 'plague on all our houses' - an abandonment of rational thought and an abandonment of any attempts at morality, ethics and self-perpetuation as humans. We find only a morass once we stop drawing lines. With nothing to see, analyze, protect, or care about, we lose all identity but 'I think therefore I am' and end up trapped in eternal solipsist narcissism, dehumanized because community is part of identity, and identity is part of humanity.

--BenK

(To reply, click here.)

One glaring problem that I see with this attempt at such an early bright line distinction, as postulated by the authors, is that at best the developmental program is in its preliminary stages. There is a production plan but you can bet there will be change orders during actual production. Yes there is a detailed plan in place, which may or may not lead to a viable baby but there are also many outside influences which can change that plan at a moments notice.

[Assume] at some point after the bright line fertilization Mom is prescribed a little thalidomide to keep her stress down. Guess what? Mom just sent a change order for the program. We've decided to reduce the size of the right arm by half - add three extra fingers to the left hand and you won't be getting feet on either leg although we will add a second 1/4 left arm just below the original plan.

This was just the most graphic example that I could think of but consider all the warnings to pregnant women about how they might harm their child's development in utero. FAS, the affects of smoking - the possible neurological effects of drug use. IMO, on a quick surface examination the bright line argument at the conception stage cannot hold water.

--morganb

(To reply, click here.)

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