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Are Chimeric Embryos Unnatural? And Does It Matter?

Concerns about our relationship with nature, including our relationship with human nature and with our own human bodies as we find them in all their variety, underlie an assortment of contemporary social debates, on topics ranging from environmental protection measures to the creation of genetically modified foods, end of life decisions, and the development of new forms of medical biotechnology. But perhaps nothing generates these concerns quite as vividly as research that involves the creation of embryos that are part human and part animal – enucleated animal eggs, for instance, with human chromosomal material.

Last week, British regulators announced that they would evaluate and might well approve two proposals for research that involve the creation of such hybrids for use in medical experiments. The British public tends to have a more lenient position on medical research than does the American, but British public opinion leaned against the creation of hybrids for research. Nearly half opposed it and just over a third favored it.

The rationale for using animal eggs is that they are much easier to obtain than human eggs. But according to a story in the Washington Post, the British worried that creating hybrids “constitutes meddling with nature and might lead to more troubling experiments.” Some feared that the hybrids would be transferred to women’s wombs and might come to term. Scientists often call hybrids chimeras, after the mythical Greek creatures that had a lion’s head, a goat’s body, and a serpent’s tail; the prospect of allowing human-animal embryos that come to term inevitably conjures up such a picture.

A scientific sanity check is in order here: if the embryo has human chromosomes, then a creature born from a hybrid embryo could not end up with animal body parts. There would be no fauns. In a sense, it might not even be “hybrid,” since instead of combining nuclear material from two species it would combine cytoplasm from one organism with nuclear material from another. (British researchers have suggested that it be called a “cytoplasmic hybrid” or a “cybrid,” although the latter term would be a dreadful mistake, as it sounds like the entity would be a cyborg – a machine-human hybrid.)

Because the cellular machinery found in the cytoplasm can be important in an organism’s development, there might be some abnormalities in a “cytoplasmic hybrid.” But assuming the entity were implanted and came to term, the human genes would direct development. The entity that emerged from the womb would have a human appearance, human behaviors, and a human genetic profile (except for the genetic material in the mitochondria). It’s hard to see how it could be regarded as anything but a human being. Further, if parents are identified genetically, then the parents of this creature would be the parents of the person who contributed the genetic material.

But there’s more to say. Parents might also be identified as those whose biological materials are conjoined to create a new being. If the enucleated egg were donated by a woman, there would clearly be a biological connection between her and the new being, and the new being might feel that the woman was a kind of “biological parent.” (In this scenario, the nucleus would contain genetic material from another person, and both that person and that person’s parents might also be said be biological parents.)

Thus we don’t need visions of fauns to have worries about meddling with nature. Merely the fact that an embryo is created, in circuitous and novel ways, from a human being and, say, a mouse, might still raise that concern.

I have argued elsewhere in this Forum that concerns about altering natural states of affairs are morally legitimate. (Here’s a piece about sports, and here’s one about livestock.) One objection often raised against appeals to nature is that the concept of nature is just incoherent: nature is often described as that realm in which humans have not interfered, but humans have interfered somehow in nearly everything on earth.

True, I suppose. Still, to say that human influence is present “somehow” in nearly everything seems unnecessarily simplistic. We can and do distinguish between different kinds and degrees of interference. Which is more natural – fresh-squeezed orange juice from an organically grown tree or Tang? There is no serious debate. One who argues “neither” is interested mostly in undermining the moral concern about nature. “Nature” is coherent enough: much of the time, we can say with reasonable confidence which of two things is the more “natural.” We can do no better for most other morally interesting concepts.

Another objection is that whether something is natural is of no particular moral bearing. That something has always happened is not a reason that it should happen.

This is also true, although only in part: surely we cannot make broad, abstract claims: not everything is better just in virtue of being natural. Would ribs meat from a genetically modified pig less desirable in virtue of the genetic modification? I don’t see why everyone should think so. But for some people, food preferences express or reflect deeply held values. If someone celebrates nature and wants to avoid unnecessarily changing it, then she may have at least one reason to go for the unmodified ribs. But even here it’s complicated: if the pig has been modified so as to be environmentally better, her desire to avoid changing natural states of affairs might lead her to prefer those ribs over others.

Concerns about nature can be legitimate factors in moral decisions, but they are only factors, and they have to be understood in a social context, and they are, so to speak, optional.

If all this is right, then at least asking how hybrid embryos square with our views about nature is appropriate. At the end of the day, though, views about nature do not seem to warrant a prohibition on the research. The relevant context here is the laboratory. Food choices and certain sporting events arguably cannot be fully understood without understanding how they connect with human attitudes about nature; not so the laboratory. What’s more, our institutions surrounding food choices and sports can be set up so as to reflect the optional nature of values about nature. Not so a universal prohibition.

Published on: September 11, 2007
Published in: Emerging Biotechnology, Science and Society

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