D. Scott Bennett, Chimera and the Continuum of Humanity: Erasing the Line of Constitutional Personhood

• Jurisdiction: United States,Federal
• Publication year: 2006
• Citation: Vol. 55 No. 2

COMMENTS

CHIMERA AND THE CONTINUUM OF HUMANITY: ERASING THE LINE OF CONSTITUTIONAL PERSONHOOD

In Minnesota, pigs are being born with human blood in their veins. In Nevada, there are sheep whose livers and hearts are largely human. In California, mice peer from their cages with human brain cells firing inside their skulls.¹

INTRODUCTION

The above quotation may sound like an excerpt from a science fiction novel, but it refers to real creatures known as "chimera," which scientists are creating with increasing frequency.²The term chimera has its origins in Greek mythology. The mythological chimera was a fire-breathing monster-with the head of a lion, the body of a goat, and the tail of a dragon-that terrorized the kingdom of Lycia.³In contemporary times, chimera have been the subject of science fiction novels, including H.G. Wells's The Island of Doctor Moreau, in which a renegade doctor surgically creates part-human and part-animal creatures.⁴

In modern biotechnology,⁵the term chimera describes an organism comprised of at least two genetically distinct populations of cells originating from independent embryos.⁶Under this biotechnological definition, any particular cell in the chimera derives from one of the parent organisms but is not a mix of the two parents as in sexual reproduction.⁷Thus, each cell in a human-mouse chimera would be either completely human or completely mouse. Chimera technology has rapidly left the realm of the hypothetical, and this technology opens up a Pandora's Box of legal and ethical questions by intimately mixing human and animal.

As an example of the types of creatures being produced by chimera technology, in early 2004 researchers at the Mayo Clinic produced chimera by injecting human stem cells⁸into forty-day-old fetal pigs.⁹Because the human cells were introduced well into fetal development, the organisms outwardly look like pigs.¹⁰However, closer examination reveals that these creatures have porcine cells and human cells mixed throughout their bodies.¹¹Unlike a human receiving a transplanted piece of animal tissue or an animal with a few human genes inserted into its genome, these chimera represent a genetic and structural mix of human and animal.¹²

Presently, Irving Weissman, the director of Stanford University's Institute of Cancer/Stem Cell Biology and Medicine, is contemplating pushing the envelope of chimera research even further by producing human-mouse chimera whose brains would be composed of one hundred percent human cells.¹³

Weissman notes that the mice would be carefully watched: if they developed a mouse brain architecture, they would be used for research, but if they developed a human brain architecture or any hint of humanness, they would be killed.¹⁴This solution hardly resolves all moral and legal issues. These biotechnology creations highlight a significant and unresolved question: Do human-animal chimera deserve constitutional protection as "persons"?

This Comment does not take a stance on whether chimera research is inherently morally, ethically, or constitutionally wrong. Instead, this Comment provides a framework for determining if and when the U.S. Constitution and the rights it confers should even be applicable to chimera and chimera research. While Congress may ban the production of constitutionally uncertain chimera in the future, it has not done so yet, and such creatures may be created in the interim.¹⁵

Personhood is the necessary threshold requirement to the application of specific constitutional rights and therefore the personhood of various types of chimera is crucial.¹⁶Given the current state of chimera technology, the division between human and animal has become a continuum, not a bright line.¹⁷Scientists can create chimera with just a few human cells, chimera with primarily human cells, and everything in between.¹⁸At some point along the spectrum between human and animal, chimera must be afforded protection under the Constitution as constitutional persons.¹⁹To do this properly, a fundamental change in the interpretation of the seemingly unambiguous constitutional term "person" is required.

Since chimera potentially erase the line between human and animal, it is doctrinally unsound to rely on a strict person/nonperson dichotomous approach to constitutional personhood.²⁰Therefore, to adequately reflect the realities of the new personhood continuum, varying levels of constitutional protection should be afforded to chimera based on a sliding scale approach to personhood.²¹The application of these varying levels of protection should be guided by the fundamental characteristics of personhood: (1) higher-level human cognitive traits and (2) the possession of crucial human biological tissues.²²Moral and ethical questions remain even under this approach; however, if human-animal chimera are to be produced, a more adaptive legal framework is needed.

Part I of this Comment provides the scientific background of chimera necessary to understand the legal and ethical issues surrounding chimera research.²³Part II describes the current state of the law on chimera, which, problematically, has thus far been largely confined to the patent arena. Part III examines what it means to be a legal and constitutional "person" at the ends of the human life span. Part IV analyzes and coalesces the various moral and ethical theories that are applicable to chimera. Part V argues that it is possible to create chimeric "persons" and proposes a more flexible and inclusive approach to constitutional personhood.

I. THE SCIENCE OF CHIMERA

To appreciate the issues surrounding human-animal chimera, it is important to understand the biotechnology that creates them. While differentiating what is and what is not a chimera can be complicated,²⁴the scientific definition is relatively straightforward: a chimera is an organism with two or more distinct populations of cells derived from separately fertilized embryos.²⁵The resulting creature can be a truly unpredictable mixture of species.²⁶Chimera are distinct from hybrids,²⁷clones,²⁸and organisms created by recombinant

DNA technology.²⁹Although it is possible to create animal-animal chimera, human-human chimera, or even chimera of more than two species,³⁰this Comment will focus on human-animal chimera.

A. Chimera Production

Presently, the most common method of producing human-animal chimera is to inject stem cells from one species into an early embryo of another species.³¹Because stem cells are able to differentiate inside the embryo and integrate themselves into all tissue types, the resulting organism is a hodge- podge of the two species.³²In recent years, experimenters have used the stem cell method to produce, for example, human-sheep and human-pig chimera.³³

So far, scientists conducting these experiments have used only animal embryos, not human ones, and have delayed the injection of the human stem cells in order to assure the chimera is essentially still a sheep or pig.³⁴There are no guarantees, however, that researchers will not cross these boundaries in the future.

While most of the recent chimera research involves the stem-cell injection method, other methods of producing chimera are available. A technique that has proved quite successful in producing animal-animal chimera involves mixing embryos of two organisms at a very early stage.³⁵In 1984, this embryonic mixing technique was used to create goat-sheep chimera, which were fittingly named "geep."³⁶The geep were successfully raised to adulthood and possessed traits of both species. The legs and skull of the geep were goat- like, the frame was that of a sheep, and the skin was covered in both the curly wool of a sheep and patches of the short, coarse hair of a goat.³⁷Given the relative ease with which the geep were produced, it should be comparatively simple to use this method to produce a human-ape chimera given the vast advances in biotechnology since 1984 and the fact that apes are more closely related to humans than sheep are to goats.³⁸Technically, chimera can also be produced by transplanting or engrafting tissues, such as an organ or heart valve, from one organism into another.³⁹

A biotechnology technique that raises many of the same issues as chimera technology is human-nonhuman nuclear transfer.⁴⁰Nuclear transfer utilizes cloning technology to transfer the cell nuclei from one species into the de- nucleated cells of another species.⁴¹The denucleated cells act as biological shells for the introduced nuclei, which take over control of the cells. In 2003, scientists in China used the nuclear transfer method to insert human DNA into denucleated rabbit eggs and allowed the embryos to develop for fourteen days.⁴²These organisms, like chimera, are morally, ethically, and legally troubling because they have a very similar biological makeup to humans.⁴³

B. The Use and Misuse of Chimera

Scientists are examining several medical and pharmaceutical uses of human-animal chimera. Because biotechnology is a rapidly changing field, the following list of three major uses is meant to be illustrative, not exhaustive. First, chimera may allow for improved testing of the benefits, side effects, and interactions of pharmaceutical drugs.⁴⁴This is because entire human cells, tissues, and organs can be present in a fully-formed organism, allowing for more direct and effective testing than can be achieved in animal studies or cell- line research.⁴⁵For example, a human-animal chimera with a fully human liver could be more effective at testing a drug's effect on the human liver than traditional testing using cultured human liver cells. Second, it may be possible to use chimera to grow organs for transplantation into humans.⁴⁶Organs with all or nearly all human cells grown in a human-animal chimera are less likely to be rejected by the recipient's immune system than traditional xenotransplants,⁴⁷and scientists have already produced chimeric sheep whose livers are eighty percent human.⁴⁸Third, chimera...