In their efforts to tackle inherited diseases and help infertile couples, scientists across the world are developing techniques and technology that ape the most basic — and morally complicated — of biological functions: human reproduction. Taken together, the work poses some troubling questions.

In the most recent research, the scientists claim to have grown eggs using stem cells scraped from anonymous human tissue. Others are trying to do the same with sperm. How long before they succeed? And could the two be combined to produce a synthetic embryo? No serious scientist advocates such a move, but as the parallel field of human cloning demonstrates, not everyone in a white coat is a serious scientist.

Further, some warn we may one day be able to incubate such fetuses outside the body, as described so memorably in Aldous Huxley’s dystopian classic, “Brave New World.” Work to develop such “artificial wombs” is already under way. So is artificial reproduction on the horizon?

“I have no doubt there are people fantasizing about creating a baby with no humans involved,” says Thomas Murray, president of the Hastings Center, a bioethics think tank in Garrison, N.Y. “I am sure there are people intrigued by that prospect, though I’m not one of them. It is never too early to start thinking about the moral implications. It’s amazing how quickly things develop and stun us.”

Those in doubt should pay a visit to the laboratory of Hung-Ching Liu, an embryologist at Cornell University in New York. In 2002, Liu stunned the world of reproductive medicine by claiming to have re-created a woman’s womb, using uterine cells grown on a biodegradable scaffold bathed in a broth of hormones and nutrients. When Liu placed fertilized human embryos created during in vitro fertilization treatment inside, they nestled into the wall of the womb and began to attach themselves to the endometrial cells that make up the lining — just as in the early stages of pregnancy. Liu stopped the experiments after a week because regulations prevent human embryos from being developed much further.

No such restrictions apply to animals and, in unpublished work, Liu says she has now grown mouse fetuses in her artificial womb for 17 of their 21-day terms. This is equivalent to about 31 weeks in humans, at which point babies have been viable for more than a month and can routinely be nurtured to normal development if born prematurely. Just as with the human embryos, the tiny bundles of mouse cells nestled into the artificial womb lining and began to attach themselves. Liu watched as blood vessels formed, then miniature placentas and, eventually, the amniotic sac — an embryo’s personal protective bubble.

Liu, of Cornell’s Center for Reproductive Medicine and Infertility, says: “Normally people don’t grow mouse embryos beyond 10 days. This goes way beyond that and forms a mouse shape housed inside a little bubble. It was wonderful. We were really amazed.”

But, peering inside, Liu could see that something had gone wrong. “The fetuses were not healthy. We could see the mouse inside but it was severely deformed.” Liu repeated the experiment more than 150 times. Not all the embryos developed, but for those that did, the story was the same. By 17 days it was clear that the fetuses were abnormal, so she pulled them out. “They were like a stillborn baby, just sitting there, doing nothing. I don’t think they were alive.”

When Liu cut them free from their amniotic sacs, the mice were dead. She thinks that the problem lies in the animals’ blood vessels, which do not form properly and so fail to circulate the required nutrients. “What other factors it needs to develop into a normal baby is still unknown. We’re only getting something that we think is close to the truth.”

Others are working at the other end of gestation, with equally startling results. A team at Temple University in Philadelphia, led by Thomas Shaffer, has developed breathable fluids that allow sheep delivered at half-term to survive outside their mothers. And scientists in the laboratory of the late Yoshinori Kuwabara in Tokyo have used tanks of synthetic amniotic fluid to incubate late-stage goat fetuses taken from pregnant animals for several weeks.

Some have speculated that the two ends of this research will eventually converge — allowing a two-cell embryo to develop into a living, breathing baby, entirely under laboratory lights.

Scott Gelfand, director of the Ethics Center at Oklahoma State University in Tulsa, was so concerned that he gathered experts together in 2002 for a conference titled “The End of Natural Motherhood: The Artificial Womb and Designer Babies.”

Murray, who attended the conference, says that while discussing the issue is easy, making it a reality is very, very difficult. “I think it is crucial for us to work out where to invest our moral anxiety, and I think that artificial wombs are not there yet. They are much more complicated than people think and not a neat lab trick like squeezing out the nucleus from a cell and putting a new one in its place.”

Although the ever-dependable Raelian cult says it has developed a device called a Babytron to incubate their clones, no reliable scientist believes that we are anywhere close to a working artificial womb capable of replacing a woman.

Embryos being made from synthetic eggs and sperm, however, is a different story. The artificial eggs that prompted the errant newspaper’s headline were prepared by a team led by Antonin Bukovsky at the University of Tennessee Graduate School of Medicine in Knoxville. Bukovsky says his technique could provide a potentially limitless supply of eggs — a scarce resource in fertility treatment and stem cell research. His claims have yet to be tested, and scientists have questioned why such groundbreaking results appeared in the little-known journal Reproductive Biology and Endocrinology, edited by Bukovsky. But it is clear in which direction research in the field is headed.

“It is not ridiculous to say this moves us toward the point where we can do completely artificial reproduction,” says Josephine Johnston, also at the Hastings Center. “But if you want a healthy baby, there are lots of easier ways and things people would rather do. It’s a bit like the whole debate in IVF and how we could design babies, but the fact is that most people don’t want to use IVF. They do it because they are desperate.”

As John Eppig, a developmental biologist at the Jackson laboratory in Bar Harbor, Maine, puts it: “I’m sure bioethicists are already thinking about this, but even if the ability to do it comes along, I don’t think it is going to replace the current method used to make babies in most homes.”

Like Liu, Eppig has been experimenting with mice, and his results also tell a cautionary tale. In 1996, Eppig succeeded in growing mouse eggs in his laboratory. He started with ovaries from newborn animals, cultured them and dissected out precursors of eggs, called oocytes, and associated cells. After careful nurturing, many of the resulting eggs began to grow when fertilized, but the 190 early-stage embryos transferred into female mice produced just one live pup. Eggbert, the first mouse born from a lab-cultured egg, was far from normal. He suffered from obesity and neurological problems.

Since then, Eppig’s team has worked to improve the culture medium used to grow the eggs, and in 2002 it reported the birth of 59 apparently healthy mice. Others are working to produce synthetic sperm and eggs from less obvious sources: the ubiquitous stem cells.

In 2003, Hans Schoeler and Karin Huebner at the University of Pennsylvania’s School of Veterinary Medicine said they had produced eggs from stem cells extracted from mouse embryos. Others, notably Toshiaki Noce at the Mitsubishi Kagaku Institute of Life Sciences in Tokyo, have tried to repeat the trick with sperm, though it is proving more difficult.

Synthetic eggs and sperm made from stem cells raise new ethical questions, mostly over parenthood. Schoeler and Huebner’s results suggest that eggs can be made even from male cells — potentially allowing a gay male couple to produce children through sexual reproduction. Contrary to some reports, the same is not true for lesbian couples. “To make a sperm you need a Y chromosome,” explains George Daley, a stem cell biologist at the Children’s Hospital in Boston. “There’s been all kind of speculation about whether you could make sperm from female cells. You can’t.”

Daley adds his voice to the chorus insisting no reputable scientists are involved in this research because they think it could be used for reproduction. “There are other issues that are more valuable to study, such as the development of the germ lineage, which has enormous implications for biology, fertility, the development of diseases and congenital defects. You can imagine all levels of bizarre scenarios but I think we need to stay focused on fundamental questions of medical importance.” Besides, he says, sperm and eggs generated from stem cells in a laboratory will probably not develop properly. “There are lots of reasons to think they are restricted or abnormal in some way and may not be able to support full development. This is a long, long way from reproduction in a dish.”

Eppig agrees: “Ethicists do need to be thinking about this and they do need to be thinking about it now. But actual applications are really not on the immediate horizon.”

Were significant advances to be made along the road of artificial reproduction and gestation, the issues would clearly be significant. “The issue with artificial wombs might not be so much in taking a fetus to term, but in using them to save very premature babies,” says Richard Ashcroft, a medical ethicist at Imperial College, London. If hospitals could use such wombs to keep babies alive that would otherwise be too premature to survive, it could well have implications for abortion law, he adds.

But as with all technological advances, new techniques are not guaranteed a market. How many couples would want to see their baby grow in an artificial womb unless there was no alternative? And as Ashcroft adds, for the vast majority of women, the importance of going through the birth process cannot be overstated.

Artificial sperm and eggs arguably raise more profound issues. Knowing that genetic material came not from living humans but from synthetic gametes grown in a lab would reinforce the distinction between parents as genetic donors and those who raise the child. For now, the sheer difficulty of perfecting the techniques necessary for fully artificial reproduction means the ethical issues are little more than talking points, says Eppig.

“All of these things are very, very hard to do. They are interesting mind games to discuss over a couple of beers after work. While we’re going to learn a lot about development from these studies, making embryos for animals and people is a long, long way off. How long? Don’t hold your breath.”

John McCloskey of the University of Ulster in Coleraine, who led the research, said: “Many of us are brought up to understand hazard as whenever you’ve had your bit of bad luck it doesn’t happen again. Lightning never strikes twice. But one great indicator that you’re going to have an earthquake is that you’ve just had one.”

He added: “These are very significant and extensive increases in stress. We cannot say for certain it will result in an earthquake, but it’s the biggest stress increase over a large area that we’ve measured since we started doing this research.”

A powerful undersea earthquake rocked parts of the region Wednesday but there were no reports of damage or casualties. The quake, which registered 6 on the Richter scale, struck about 19 miles beneath the seabed off Aceh province in Indonesia but did not cause a tsunami.

The new study shows that one of the regions at increased risk of a more powerful event is a 31-mile stretch of the undersea Sunda trench, next to the 745-mile-long zone that ruptured in December. Earthquakes in the Sunda trench triggered fatal tsunamis in 1833 and 1861.

Not all big undersea earthquakes cause tsunamis, but the scientists say their results emphasize the urgent need for a warning system in the Indian Ocean. Countries in the region and U.N. experts agreed on plans for a system last week at a meeting in Paris, but it will not be completed until the end of next year. Until the network of tidal gauges and seabed sensors is in place, Japan and the United States plan to issue alerts on seismic activity in the Indian Ocean.

The second area of concern identified in the new research is a 185-mile region of fault running directly beneath the island of Sumatra, close to the city of Banda Aceh, which was devastated in December and where rebuilding work is underway. The scientists estimate that stress in the Sunda trench region has increased by up to five bars; in the Sumatra fault it has been forced up by as much as nine bars.

McCloskey said there is a worrying recent precedent to consider: In 1998 seismologist Suleyman Nalbant, one of the authors of the new study, used the same technique to show that local seismic activity had increased stress by two bars on a 31-mile stretch of the Anatolian fault in Turkey, which has a very similar structure to the Sumatra fault. Less than 18 months later, the Turkish fault gave way near the city of Izmit and triggered a magnitude 7.4 earthquake that killed 20,000 people. He also warned that earthquakes in subduction zones — where one continental plate passes underneath another, as happens at the Indian Ocean boundary — frequently have struck in pairs.

In the Nankai trough to the southeast of Japan, five of the seven large earthquakes over the last 1,500 years have been followed by a similar event within five years. Three occurred within 12 months.

McCloskey said: “It’s by studying and reanalyzing what happened in the past that we are able to have some confidence in the relationship between the stresses we’re measuring and the occurrence of other earthquakes. But it should be stressed that the mapping is not one to one. It does not mean there will be another earthquake within a year or two, but certainly the risk has increased significantly as a result of what happened in December.”

His team used computer simulations of the earthquake prepared by an American team at Caltech in Pasadena, Calif., to re-create movement of the surrounding area. Because some regions of the affected fault slipped further than others, the resulting redistribution of stress through the ground was patchy and uneven — meaning seismologists could not be sure at first whether the risk of a second quake was raised or lowered.

To find out, McCloskey’s group used mathematical models of elastic materials, which essentially view the Earth as a giant rubber ball. For several points along the faults in the two danger zones they worked out whether the movement of the surrounding rocks freed the two surfaces to slide past each other or clamped them together, making an earthquake more or less likely. The results appear in the journal Nature.

Peter Styles, the president of the Geological Society, said: “It has become apparent over the last 10 years that when a major earthquake occurs it changes the stress in adjacent areas. Sometimes this can serve to lock the fault, but sometimes it can make another failure more likely. Every effort should be made to ensure that appropriate monitoring technologies and communication protocols are put in place to monitor the Indian Ocean.”

Nick Ambraseys, a seismologist at Imperial College in London, said: “There is nothing in [the new study] that enables, with any degree of certainty, the prediction of the immediacy of the next earthquake — except that an earthquake such as those of 1833 and 1861 is likely to occur sometime in the future. False alarms and inaccurate timing could create more problems than already exist.”

In separate research, marine scientists in the United States have highlighted the risk of a tsunami in the Caribbean, where there is no warning system. The team from the University of North Carolina and the University of Texas say that more than 35 million people could be affected if a powerful earthquake struck along the boundary between the North American and Caribbean tectonic plates. At least 10 significant tsunamis have been recorded in the region since 1492, six of which are known to have caused loss of life.

May’s warning coincides with a meeting of climate change skeptics Thursday at the Royal Institution in London organized by a British group, the Scientific Alliance, which has links to U.S. oil company ExxonMobil through a collaboration with a U.S. institute. Last month the Scientific Alliance published a joint report with the George C. Marshall Institute in Washington that claimed to “undermine” climate change claims. The Marshall Institute received 51,000 pounds from ExxonMobil for its “global climate change program” in 2003 and an undisclosed sum this month.

May’s warning comes as British scientists, in the journal Nature, show that emissions of carbon dioxide could have a more dramatic effect on climate than thought. They say the average temperature could rise 11 degrees Celsius, even if atmospheric carbon dioxide were limited to the levels expected in 2050.

David Frame, who coordinated the climate prediction experiment, said: “If the real-world response were anywhere near the upper end of our range, even today’s levels of greenhouse gases could already be dangerously high.” Emission limits such as those in the Kyoto protocol would hit oil firms because the bulk of greenhouse gases come from burning fossil-fuel products.

May writes that during the 1990s, parts of the U.S. oil industry funded skeptics who opposed action to tackle climate change. A Scientific Alliance spokesman said Thursday’s meeting was sponsored but that the funders did not influence policies. ExxonMobil said it was not involved.

One advisor is Sallie Baliunas, an astrophysicist at the Harvard Smithsonian Center, who is linked to the Marshall Institute. In 1998 Baliunas co-wrote an article that argued for the release of more carbon dioxide. It was mass-mailed to U.S. scientists with a petition asking them to reject Kyoto.

Tony Blair, at the World Economic Forum in Davos, Swizerland, Wednesday urged President Bush to sign a climate change accord. He said climate change was “not universally accepted,” but evidence of its danger had been “clearly and persuasively advocated” by a very large number of “independent voices.”

Miodrag Stojkovic, from the university’s Institute of Human Genetics, said: “We are ready to go as soon as the paperwork is sorted out. It has taken a year of work, and I am most pleased that the HFEA has recognized the potential of this technology in modern medicine.”

The Newcastle team will use the same technique used to create Dolly the sheep. They plan to insert DNA from skin cells into eggs left over from IVF treatment, which have had their own genetic material removed. Nurturing the eggs for six to eight days produces a tiny ball of around 100 cells, no bigger than a pinhead, from which stem cells can be extracted.

If the skin DNA was taken from a diabetic, then, in theory, the resulting embryonic stem cells could be grown into new pancreatic tissue and transplanted back into the patient with no risk of rejection.

“What we want to do is to see if these embryonic stem cells have the ability to differentiate into insulin-producing cells,” said Dr. Stojkovic. The scientists hope to produce the first stem cells within two years, though it could take at least five before any new therapies are tested in clinical trials.

Cloning human embryos to make babies is outlawed in the U.K., but so-called therapeutic cloning, where the embryo is destroyed after the stem cells are extracted, was made legal under strict guidelines in 2002.

Last year the Newcastle scientists became one of the first two groups in Britain to derive embryonic stem cells from spare IVF embryos. It asked the HFEA to allow the cloning research in February.

The chairwoman of the HFEA, Suzi Leather, said: “After careful consideration of … the project, the committee agreed to grant an initial one-year research license. This is an important area of research and a responsible use of technology.”

The first task for the Newcastle scientists will be to repeat the work of colleagues in South Korea, who in February cloned the world’s first human embryos and extracted stem cells. The South Korean team used dozens of fresh eggs from volunteers, which are more suitable for cloning than those left over after IVF.

Pro-life groups said they were taking legal advice in a bid to overturn the ruling. Jack Scarisbrick, national chairman of the group Life, said: “The decision is not unexpected given the HFEA’s track record.

“Therapeutic cloning involves the manufacture of a new kind of human being with the express purpose of destroying that life once stem cells have been stripped from it. It is … trivialization of human life of a most frightening kind.”

The U.N. will discuss moves to ban reproductive and therapeutic cloning in October.