Transgenic Chimeras

Jason Robert and Françoise Baylis (2003) focus primarily on "human-to-animal embryonic chimeras" (emphasis added). The ethical issues they discuss, however, surround not the status of transgenic blastocysts and early embryos cultured a few days in vitro for research and then discarded but an "animal born following this research;" that is, such an embryo brought to term. An obvious example would be the Harvard OncoMouse, which in 1988 was genetically engineered to contain a human cancer-causing gene. Thousands of different transgenic mice have by now been engineered in laboratories to be discarded after a few experiments. Such a creature is not part human and part mouse; it is (as Robert and Baylis suggest) "just a mouse with a few human cells."

Robert and Baylis ask, "But what if those cells are in the brain, or the gonads? What if the chimeric mouse has human sperm? And what if that mouse were to mate with a chimeric mouse with human eggs?"

I agree that in a fantastic science-fiction scenario, one too incredible for any but the most lurid cinema, a mad geneticist could produce a transgenic embryo, implant it in a surrogate mother, and bring to term a Caliban that is neither clearly animal nor clearly human. As Robert and Baylis point out, this would "constitute an unacceptable threat to valuable and valued conceptual, social, and moral boundaries that set human beings apart from all other creatures."

Robert and Baylis do not assert that every animal that expresses a human gene, such as the OncoMouse, constitutes an unacceptable threat to our moral intuitions. The mere inclusion of human DNA in an animal—a pig engineered so that its organs carry a surface protein that facilitates xenotransplantation, for example—does not raise any of the moral issues Robert and Baylis describe. One would celebrate such an animal as "some pig" and as "terrific," but one cannot doubt that "pigs are pigs." Robert and Baylis are not naive genetic essentialists who assert that the amount of "human" DNA in an organism correlates with its moral status as a person. Indeed, they point out that "there is little (if any) uniquely human DNA."

What sort of animal would "threaten to break down the social dividing line between human beings and nonhuman beings"? If genetic or other research manages to control the process of aging and thus produce a race of immortals, this could very well separate normal human beings from what would be effectively gods. This is unlikely to involve hybridization of human beings with other animals. A different possibility might involve the creation of a macaronic beast such as the fabled centaur, half-man and half-horse, said to inhabit the mountains of Thessaly. A centaur might be easier to produce, anyway, than the half-mouse, half-human Robert and Baylis describe.

A race of centaurs would surely baffle our moral intuitions, categories, and assumptions, as Roberts and Baylis suggest, but this might have nothing to do with their genome. One could speculate that the mad scientist who produces these creatures works at the level of RNA not DNA—he takes control of the vagaries of development to produce, by dictating the way proteins fold, centaurs, for example, from human embryos. This seems as likely a way as any to produce such a human-beast hybrid. One can imagine manipulating development at many levels beyond the genome to create fantastic organisms. The centaur becomes morally problematic not because of its genotype but its phenotype—not because of his, her, or its genetic code, which could vary, but because of the concoction of properties that result from the entire process of development.

Fortunately, no project contemplated by scientists—or even in sight—raises the moral ambiguities that concern Robert and Baylis. None of the four "examples of relevant work" they mention intends or contemplates creating animals from chimeric embryos; in fact, two do not involve embryos at all. According to the newspaper account Robert and Baylis cite, the...