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.

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."