NOT HUMAN, NO PROBLEM:

How to Farm Stem Cells Without Losing Your Soul: A solution to the stem cell dilemma that even the Vatican can love. (Clive Thompson, Wired)

William Hurlbut clicks his laptop, and an x-ray pops up on the projection screen behind him. It's a picture of a tumor in a woman's ovary - a ghostly blob floating near the spine. In the middle are several strange, Chiclet-shaped nodules. "Those white opacities," Hurlbut says, "are actually fully formed teeth."

A few audience members blanch. Though we're in an ordinary conference room in Rome, it feels like church. The seats are filled with some of the Vatican's top thinkers, including a dozen men in clerical dress, a nun in a flowing brown habit, and a Dominican priest whose prayer beads quietly clatter. Hurlbut, a bioethicist from Stanford, has traveled here to tell them about a new way to create human embryonic stem cells.

As you might expect, the Vatican is vehemently opposed to embryonic stem cell science. President Bush is also wary, and two years ago he all but banned federal funding for it. But most medical scientists remain convinced that stem cells hold the key to a new kind of healing: regenerative medicine. Embryonic stem cells are pluripotent, meaning that they have the ability to develop into any type of human tissue. If that capacity could be harnessed and directed, injury and disease need no longer be crippling. For example, new neurons grown from stem cells might reverse the damage from Alzheimer's and repair severed spinal cords. But the research requires growing - and destroying - embryos in the lab. Hurlbut, however, claims he has a method for harvesting embryonic stem cells without killing human embryos.

The proof is projected on the screen. The x-ray shows a teratoma, a naturally occurring tumor that grows from an egg or sperm cell. Like an embryo, a teratoma produces stem cells. But the teratoma does not have the right balance of gene expression to create a fully integrated organism. So it grows into a dense ball of teeth, hair, and skin, a ghastly grab bag of organs like some randomly constructed Frankenstein. Hurlbut points to the x-ray. "They're about the ugliest thing in medicine," he says, "but they might offer us a solution to our stem cell dilemma."

In a bit of diplomacy that may satisfy both the scientists and the theologians, Hurlbut advocates genetically altering cloned embryos so, like a teratoma, they wouldn't have the DNA necessary to become viable humans. For the first few days of existence, they would grow normally and produce stem cells, but then die when a critical embryonic component - say, a placenta - failed to emerge. "They would have no coherent drive in the direction of mature human form," Hurlbut tells the crowd. "It's analogous to growing skin in a tissue culture. Such an entity would never rise to the level of a human being." You could grow them in vats, kill them at will, and never risk offending God. As both a medical doctor and a deeply religious Christian, Hurlbut borrows from each side: It's a theological breakthrough in the form of a scientific technique. [...]

Central to this debate is the perennial question: When does life begin? Science and religion have radically different answers. Scientists know that nerve and brain cells emerge shortly after conception. As a consequence, stem cell researchers generally agree that research should be done on embryos less than two weeks old. "Up to 14 days, you don't have a creature with a brain in it, so you can't even consider it to be, say, brain-dead," says Michael Gazzaniga, who heads Dartmouth College's program in cognitive neuroscience. "If you accept that, then there's no problem using embryos for research." The premise here is that the brain makes a person a person, a tradition that stretches back to Descartes' "I think, therefore I am."

Christian critics have a more clear-cut view: God endows every embryo with a soul at conception. So intentionally destroying an embryo is murder - even if it's only one-cell big. Theologians typically define the embryo in terms of its human "trajectory." Since every fertilized egg cell has the inherent potential to become a fully formed adult, they argue, interrupting that process at any point - from conception to birth to nursing home - is to disrupt a sacred process.

Hurlbut has sided with pro-life theologians ever since finding faith in his twenties. (He describes himself as a "generic Christian" who goes to church at a variety of services.) "This idea that an embryo becomes a person only at day 14 is truly pseudoscientific," he says. "It's completely arbitrary." He's a vocal opponent of abortion, a position that hasn't won him many fans on the Stanford campus, where he helped develop the university's bioethics curriculum in 1989. "I've gotten a lot of heat," he says. "I can't say I've liked it."

Ironically, Hurlbut's idea came about not in spite of his piety but because of it. Instead of dismissing the theological concept of an embryo's trajectory to humanhood, he seized it, seeing a scientific opportunity. Would it be possible, he wondered, to engineer embryos that didn't have human potential yet otherwise behaved normally?