Quotes of the Day

Imagine you could unlock the secrets of Alzheimer's or Parkinson’s disease just by dissecting the brains of a few mice. Now imagine that the reason those mice were so revealing was because those brains were at least partly human?

And what if some of those specially bred mice started showing a particular fondness for Mozart? Or poker? Would it still be OK to cut them open and look inside?

It is questions like these, which have hovered around the Stanford researchers who have been working on growing human brain cells in mice, that gave rise to one of the more surprising moments in President Bush’s otherwise unsurprising speech Tuesday night.

There are always some weird encoded messages buried in a State of the Union address, the warning aimed at some particular enemy or committee chairman, the pat on the back for a friend. The commentariat runs a virtual spreadsheet, parsing applause lines, assessing the meaning of devoting 30 seconds of a 55-minute speech to the fate of New Orleans.

But in President Bush’s speech the reference that produced the greatest mystery, and mockery, was his call for Congress to ban the sale or patenting of human embryos and the creation of “human-animal hybrids.” “Human life is a gift from our Creator,” he said, “and that gift should never be discarded, devalued, or put up for sale.”

This was roundly applauded by people at the speech-watching party at the conservative Family Research Council, who understood exactly what the President was saying and why he was saying it. As for the rest of the audience, its curiosity was sufficiently piqued that human-animal hybrid was among the most searched-for terms on the Internet the next day.

The President’s critics had fun denouncing him for gratuitous bias against centaurs and mermaids. But as the White House well knows, this subject has become a challenge for bioethicists trying to figure out where to draw the lines at a time when the edges of science stretch past its traditional ethics.

American researchers have created pigs with human blood, sheep with partially human brains, livers, hearts, and of course, the brainy mice. Such experiments are grounded in all kinds of hopes: hope for a way to relieve the heartbreaking shortage of organs for transplant, for example, or for testing new drugs and treatments on a more nearly human animal to better judge what works. Other researchers are introducing animal DNA into human embryos as a kind of marker, to help them understand how disease develops. Some research involves the intentional creation and destruction of human embryos, however, which is controversial. “I’m afraid that wasn’t the most precise moment of the speech,” argues University of Pennsylvania bioethicist Arthur Caplan. “The image he used was something like a minotaur, like he was trying to prohibit the creation of half-man, half-bull creatures. No one’s interested in doing that and it’s probably biologically impossible to do that. But what he was doing was making a nod towards the pro-life base by saying ‘I don’t want embryos destroyed.’ He inadvertently wound up calling for a ban on the transplant kind of research, which I don’t really think he wants to oppose.”

So far the U.S. has not quite worked out how to regulate the creation of what are called chimeras, after the mythical creature that was part lion, part serpent, part goat. Canada last year passed a law that made it illegal to grow animal cells in a human embryo, or human cells in an animal embryo. Last spring the National Academy of Sciences was more lenient: it affirmed the potential research value of mixing human and animal cells, but drew the line at seeding any primates with human cells—at least for now—and urged that new experiments at least first be run past an expert ethics board.

There will always be absolutists who believe that any limits on research are born of ignorance or superstition, squaring off against those who note that you can’t spell science without s-i-n. But for everyone else caught between the hope for new cures, and fears of powers that, once unleashed, would forever change the very nature of our humanity, these are hard questions, more than worthy of the President’s time, and our attention.

• Nancy Gibbs
• What's the problem with human-animal hybrids?