It's nothing new for the scientific enterprise to be shaped by the society that underwrites it. From Galileo to recombinant DNA researchers, from the Manhattan Project to the Human Genome Project, we have a long tradition of scientists responding to ethical or religious guidelines that might be in conflict with their own methods and goals.

The give-and-take keeps the whole enterprise honest. Indeed, the science itself sometimes benefits: When animal rights activists in the 1970s pushed for better experimental conditions for lab animals, for example, the scientific results were more accurate because the animals were less stressed.

But the latest developments in human embryonic stem cell research are different. Investigators are now designing their experiments specifically to accommodate the concerns of their critics. And allowing activists to call the scientific shots is more than unprecedented -- it's backward. It twists the very essence of scientific experiments -- that they're designed to consider scientific questions.

Ever since President Bush declared in August 2001 that the federal government would not support human embryonic stem cell research (except for work on the few cell cultures that had already been created), American scientists have done what they could to conduct their research anyway -- not on the sly, but by relying on funding sources that don't involve the federal government. In the intervening time, the science of human embryonic stem cell research has developed rapidly, despite the lack of federal oversight.

I consider the development a good thing; I'm a supporter of stem cell research. And I know, from having studied the history of in vitro fertilization, that the entire field of assisted reproduction has grown up without a penny from the federal government, which since the days of President Gerald Ford has refused to support research involving human embryos.

But recently we've started diverging from history. A pair of reports in the journal Nature last month makes it clear that scientists are no longer just going along asking their own questions and cobbling together the money to do so from state and private sources. Now they are actually tweaking their techniques in a way that they hope will make their critics' concerns moot. And at least some hope to get federal support for their work.

In the Nature articles, scientists offered two different approaches to mollifying their opponents. One method, developed by Robert Lanza of Advanced Cell Technology of Worcester, Mass., involved pulling off a single cell from a very early embryo, a microscopic mass consisting of only eight cells, to allow the remaining seven-celled mass to develop into a blastocyst and to use the single cell as a source of embryonic stem cells. But this seems little more than a shell game. Yes, a viable embryo is likely to come out of the arrangement, but why don't the opponents worry about the sacrifice of that single cell? The justification I've heard is that since the blastocyst is allowed to go on to turn into a full-fledged embryo -- though possibly with a greater risk of encountering problems with implantation or fetal development -- then nothing has really been sacrificed in order to extract the stem cells.

The second technique, developed by Alexander Meissner and Rudolf Jaenisch at Massachusetts Institute of Technology, has the support of a member of the President's Council on Bioethics, William Hurlbut of Stanford University, who proposed it hypothetically several months ago. The MIT method involves turning off certain genes to make it impossible for the embryo to organize itself into a coherent mass of cells. It's like a model airplane kit without the glue, as Hurlbut put it last week at a panel discussion on the ethics of stem cell research sponsored by the Genetics and Public Policy Center of Johns Hopkins University. "That is, you can produce the parts," he said, "but no possibility of interaction among the parts." Therefore, according to Hurlbut, the embryo isn't really an embryo at all. It is, as he put it, a "biological artifact."

Some religious groups, including some Catholics, have written to Hurlbut in support of this proposal, believing this twist is sufficient to make the research ethically acceptable. But if creating life in the lab is ethically objectionable, why is it better to create defective life in the lab? And, more to the point, what have the scientists done to these "biological artifacts" when they started mucking about in the DNA? When they switched off the gene responsible for implantation, maybe they also removed some important genetic information without which the derived stem cells would be useless, or even dangerous to the patients who receive the supposedly curative cells. That's the real risk.

This is not to suggest that stem cell scientists should work in an ethical vacuum. "Science is a social and political activity," noted Paul Root Wolpe, president-elect of the American Society of Bioethics and Humanities, in a recent e-mail. Religious objections have stopped much science in its tracks. But typically, the objections have been less about the technique itself than about the probable outcome of the research, according to Wolpe. Many studies in human sexuality, for instance, have been stopped or redesigned because of concerns about what the studies would find.

Some Catholic scientists worked on the birth control pill as a way around their church's objection to condoms and diaphragms. Even though the research was scientifically successful, leading to a highly effective form of contraception with relatively few side effects, it turned out to be a failure when judged according to its original rationale: The Catholic Church ultimately made no moral distinction between the pill and other methods of birth control, prohibiting them all.

In studies of genetics and crime, Wolpe notes, the roadblocks have come from the other side of the political spectrum, with some liberal critics halting studies that seemed likely to focus excessively on African Americans or other minorities.

Then there have been the religious and cultural mores that have limited the use of certain new technologies. When anesthesia was first developed in the 19th century for pain relief in childbirth, some churches were opposed to it, points out LeRoy Walters, a professor of Christian ethics at Georgetown University. In the Victorian era, says Walters, some believed that obstetrical anesthesia would go against the biblical edict that "in pain shalt thou bring forth children."

But no matter how far back you go in teasing out the relationship between science and religion -- back to Copernicus's day, when his finding that the earth revolved around the sun ran counter to Church teachings of a geocentric universe -- there is no perfect analogy to the human embryonic stem cell tweaking now going on. As Wolpe puts it, "It is a unique event, and so the demands are also unique."

Ironically, some critics of stem cell tweaking see an analogy not in science, but in religion. "There's a long history of using science to get around religious issues, otherwise we'd be sitting in the dark on the Sabbath," said Laurie Zoloth, a medical ethicist at Northwestern University, at the Genetics and Public Policy Center panel last week. "Whenever you have an absolute rule in a rule-based system," she said, whether in observant Judaism or in following the federal restrictions on embryonic stem cell research, people "figure out some way to stay within the confines of the rule" and still do what they want to do. These latest experiments, she said, were "something like tofu cheeseburgers," a compromise created for Jews following kosher laws that forbid mixing meat and dairy in the same meal.

And scientific good can come from adjusting to ethical concerns, as the example of animal experimentation shows. Not only were research results more reliable when the laboratory animals were subjected to less stress in response to activists' concerns, but when non-animal models were used instead, the experiments were often less costly and more easily reproduced.

Could a good outcome happen with stem cell research, too, as investigators begin designing experiments to satisfy their critics? Perhaps. But there's a greater danger here than there was with animal experimentation. The danger is that stem cell scientists will address what they believe to be their critics' major stumbling blocks in a way that both subverts the science and fails to respond to the critics -- the worst of both worlds. "How many hoops do you have to go through as a scientist," George Daley, a stem cell researcher at Harvard University, was quoted as saying when the Nature articles appeared, "when you don't think you are doing anything wrong?" It's in trying to parse out religious objections they don't always share or even understand that scientists can run into trouble.

Author's e-mail:

henigoutlook@yahoo.com

Robin Marantz Henig, a contributing writer for the New York Times Magazine, is the author of "Pandora's Baby: How the First Test Tube Babies Sparked the Reproductive Revolution" (Houghton Mifflin).