Friday, December 10, 2004
Greely and his colleagues did not conclude that such experiments should never be done. Indeed, he and many other philosophers have been wrestling with the question of why so many people believe it is wrong to breach the species barrier.
Does the repugnance reflect an understanding of an important natural law? Or is it just another cultural bias, like the once widespread rejection of interracial marriage?
This is not, of course, a new idea. H.G. Wells wrote "The Island of Dr. Moreau" in 1896, after all, and I just read something similar by Robin Cook called "Chromosome 6" a few years ago. In the Robin Cook book, scientists developed apes with genetically identical organs to wealthy humans. The problem was, the apes (kept on an island) became smarter than normal apes, developed fire and stone tools and when, just when, do human laws kick in for animals who are part human?
For the record, I don't believe the human species ever had a "widespread repugnance" of interracial marriage and if scientists have lost the ability to feel revulsion when considering growing human fetuses inside animals then perhaps they should stop gazing at their own navels and spend a little time holding babies or, better yet, mothers' hands in pediatrics ICU.
The most radical experiment, still not conducted, would be to inject human stem cells into an animal embryo and then transfer that chimeric embryo into an animal's womb. Scientists suspect the proliferating human cells would spread throughout the animal embryo as it matured into a fetus and integrate themselves into every organ.
Such "humanized" animals could have countless uses. They would almost certainly provide better ways to test a new drug's efficacy and toxicity, for example, than the ordinary mice typically used today.
But few scientists are eager to do that experiment. The risk, they say, is that some human cells will find their way to the developing testes or ovaries, where they might grow into human sperm and eggs. If two such chimeras — say, mice — were to mate, a human embryo might form, trapped in a mouse.
Not everyone agrees that this would be a terrible result.
"What would be so dreadful?" asked Ann McLaren, a renowned developmental biologist at the University of Cambridge in England. After all, she said, no human embryo could develop successfully in a mouse womb. It would simply die, she told the academy. No harm done.
No harm done. Here, I think we would have an ally in PETA (People for the Ethical Treatment of Animals). Even if PETA doesn't care about the human baby dying, perhaps they would raise a ruckus about the mice.