Chimeras, Hybrids, and Interspecies Research: Politics and Policymaking

Chapter 2. Hybrids

Chapter 2 Hybrids THE IDEA OF A HYBRID is a powerful symbol, and the animal-human hybrid is a particularly well-known metaphor for research run amok. The thought of hybrids gives skeptics reasons to be wary about biotechnology ; for example, in a 2004 report the President’s Council on Bioethics (PCB) urged a “bright line” to be drawn against fertilizing human eggs with animal sperm or vice versa: “One bright line should be drawn at the creation of animal-human hybrid embryos, produced ex vivo by fertilization of human egg by animal (for example, chimpanzee) sperm (or the reverse)” (President’s Council on Bioethics 2004, 220). The animal-human hybrid is a sufficiently disconcerting scenario as to have been equated in the early years of modern biotechnology with the worst outcomes at the bottom of the slippery slope. The hybrid is a metaphor for biotechnology leading to the downgrading and depersonalization of humans as work horses or, conversely, to the elevation of animals to traits of greater cunning, prowess, and aggression. It is a symbol of uncertainty about the biotechnological future, and it has provoked calls by some to enact legally enforced bans to ensure that hybrids not be created. The targeting of hybrids for regulatory limits is itself ironic given the chasm between actual and imagined hybrids. Technically, a hybrid is an organism resulting from fertilization of the egg of one species with the sperm of another. Under this definition, true hybrids are rare; they are not easy to create, and there is little need if any for them in biomedical research. The imagined hybrid, however, presents dramatic fodder for fiction and fantasy, especially as typified by the humanzee, which would in fact meet the criteria for a hybrid. Nevertheless, not even so-called hybrids in fiction meet these criteria. H. G. Wells’s novel, The Island of 59 60 Chapter 2 Dr. Moreau, for example, features the Leopard Man, Hairy Man, Swine Man, Swine Woman, Saint Bernard Dog Man, and others who represent hybrids. They are a fictional form of multispecies chimeras, however, not hybrids. Dr. Moreau created the beast people by subjecting animals to crude cut-and-paste surgery using tissue and organ transplantation, not by cross-fertilization (Wells 1993). A satirical Internet image following the denunciation of animal-human hybrids in the 2006 U.S. Presidential address pitched Human-Animal Hybrid t-shirts featuring the cartoon profile of a monkey walking on all fours. Although the vertically curled tail and the four-legged gait were those of a monkey, the feet and necktie hanging from the creature’s neck were detectably human (Tester 2006). Even this being was not necessarily a hybrid, however: It more likely reflected high-tech transgenic manipulations and low-tech sartorial choices rather than full fertilization using monkey and human gametes. In short, actual animal-human hybrids may be as scarce in fiction as they are in fact. HYBRIDS IN NATURE Hybrids are organisms in which a member of one species contributes the egg and a member of a second species contributes the spermatozoan. Hybrids have genes from each parental species in all their cells; the cells, in other words, “carry roughly equal genetic contributions from two distinct species” (ISSCR 2006, 14). Animal-animal hybrids are harder to produce than chimeras and will survive only if fertilization is between closely related species (ISSCR 2006, 14). Species are regarded as “groups of interbreeding natural populations that are reproductively isolated from other such groups” (Ridley 1996, 403). An array of biological and social barriers stands in the way of interspecies reproduction, including differing numbers of chromosomes and other hurdles that make successful hybridization between animal species rare. Intraspecies cross-bred animals, on the other hand, are relatively common, but they are not technically hybrids because their parents are different subspecies within the same species. A Great Dane, a Basset hound, and a Chihuahua, for example, are all subspecies of the domesticated dog, Canis lupus familiaris (Items of Interest n.d., 1). Hybrids 61 Although hybrids rarely occur in nature, they can occur with the assistance of breeders. For example, in the 1800s, breeders in India interbred tigers and lions as gifts for English monarchs (Liger n.d., 1). Because such animals live in different parts of the world, they would not normally mate. Approximately a dozen ligers—the offspring of a male lion and female tiger (Panthera X leogris)—exist in...