Mixing Humans and Animals for Science

Feb. 7, 2005 — -- Animal-human hybrids have long been the stuff of fairy tales and myths -- from the half-man, half-horse centaur to singing mermaids.

Now the swift pace of genetic engineering has some worried that such mixed creatures, known as chimeras after the fabulous beasts of Greek mythology, are making the leap from the pages of fiction to reality.

While scientists argue that research would likely never go so far as to create entirely new, living species -- even if it could -- activists say the march toward building full-blown, genetically engineered human-animal hybrids has already begun.

In the coming months, a number of measures, from a patent filed by activists opposed to such research to lists of recommendations from the National Academy of Sciences and the President's Council on Bioethics, could influence how fast and how far such projects will proceed in the United States.

Broad Field, But Slippery Slope?

Those opposed to chimera research argue scientists have already started down a slippery slope. They point to recent hallmarks, like the researchers in China who announced in 2003 that they had used cloning techniques to create embryos containing a mix of human and rabbit genes. Or the Stanford geneticist who injected human brain stem cells into mouse fetuses last year to create mice whose brains are about 1 percent human.

A list of guidelines expected from the National Academy of Science later this month or in early March would address the growing number of questions surrounding research that mixes human and animal genetic material. The group's suggestions could have implications for future federal legislation since it has advised the government on such matters in the past. Already, members of the President's Council on Bioethics have said efforts to grow a human embryo inside an animal's womb should be banned, although they stopped short of issuing suggestions to regulate such practices.

Scientists say mixing human and animal material is not always as ghastly as it may sound. In fact, researchers have been doing it for decades to isolate genes responsible for various conditions. Pig heart valves have been used to heal human hearts and scientists have long placed human genetic material in other animals to understand the genes' functions.

"The reason for doing this is you can watch the function of a gene or cell and it stands out because it is operating within a different species," said Douglas Melton, a cell biologist and stem cell researcher at Harvard University. "It's so important that it's hard to imagine it should not be done."

To the north, the Canadian government has drawn a line by passing legislation that bans the creation of entire embryos of mixed human and animal genes. Rather than targeting specific genes, like those of the pancreas, brain or kidney, this practice creates a whole species with mixed genes throughout its body.

The difference is illustrated by the Chinese research team's project and the work at Stanford. The Chinese researchers created entire embryos containing both human and rabbit genes by implanting human skin cells into a rabbit egg. The hybrid embryos developed in petri dishes for several days and were then destroyed. In its report to the journal Nature, the team said its work could lead to a valuable new source of embryonic stem cells.

Meanwhile, Irv Weissman of Stanford University's Institute of Cancer and Stem Cell Biology has created mice with human neural cells within their brains. So far the models his team has created have brains with 1 percent human brain cells. He is considering creating mice with all-human brain cells, but is reportedly awaiting further guidance before proceeding.

Weissman, who did not return phone calls, has said the research creates valuable animal models that can shed light on what happens when brain cells malfunction and cause diseases like Alzheimer's and Parkinson's.

Playing God

The goal of such research is well-intended -- and, as Melton points out, it would seem ethically preferable to creating and testing embryos that are entirely human. But some ask, does introducing human genetic material into an animal create a new kind of being that then warrants protection?

"How human does an animal have to be to merit the protection of human rights?" said Rifkin. "How human is a mouse with a human brain? This is something that I don't think we're wise enough to dictate."

To push his point, Rifkin, along with New York Medical College biologist Stuart Newman, filed patent applications for a human-animal chimera. The pair hopes that by forcing the U.S. Patent Office to make a decision about a patent for, say, a half-human, half-monkey creature, they will force all such research to a halt.

"If we win the patent, we could hold up patents for all other [human-animal hybrid] research for the next 15 years," Rifkin said. "If we lose, it means the office won't grant such a patent and no one else could get one. It's a Catch-22 for the industry."

Rifkin and Newman first filed such a patent seven years ago, a wait that they claim is the longest for the office. They expect to hear the verdict soon.

Many in the research field see Rifkin's tactic as an overreaction. Sean Tipton of the American Society for Reproductive Medicine argues research that combines human and animal material could lead to enormous progress in helping infertile couples. He says most, if not all, hybrid research targets such higher causes and is not designed to create entirely new species.

"If you're talking about producing new species, then, yeah, that needs to be treated with caution," he said. "But you also don't want to pass legislation because of fears stemming from science fiction."

Robin Alta Charo, associate dean of law and a professor of bioethics at the University of Wisconsin at Madison, further argues that any research combining human and animal materials is already covered under existing laws and agencies.

She points out that the Animal Welfare Act would ensure any kind of chimera species would be protected and treated humanely -- or never created at all, depending on the case. And the Food and Drug Administration has authority when it comes to transplantations, since they would be concerned about new diseases springing up from combining species.

Any further concerns, she says, stem from broader, more philosophical issues, which have existed as long as science, itself.

"This is part of a deeper argument about how much social control you want over the direction that science takes," she said. "It's an argument that goes back millennia from Galileo and the church to the uproar over autopsies to in-vitro fertilization. Science has always unsettled social norms."