Does anyone remember the clamor and furor that surrounded the birth of the first test-tube baby? After Louise Brown was born in 1978 as a result of in vitro fertilization, there was an outburst of criticism that IVF was crackpot science and those responsible were monsters meddling with an intimate process best left to nature. We were headed down a “slippery slope” leading to eugenics, deformed babies, and doctors playing God. So we were warned. By now, of course, IVF is an accepted part of our lives that has enabled millions of couples to have normal and healthy children. We have all learned that the benefits far outweigh the risks.

We should keep this experience in mind as we enter the increasingly acrimonious debate over the hot-button questions of human cloning and embryonic stem cell research, issues triggered by British geneticist Ian Wilmut’s success in cloning a large adult mammal in 1996, a sheep named Dolly. His story of the momentous event and its consequences is told in “After Dolly: The Uses and Misuses of Human Cloning” (W.W. Norton, 256 pages, $24.95). The book is unusual in that it combines in one narrative a vivid first-person scientific account with a discussion of the moral and ethical issues that have emerged, inevitably, from this research. This is unfiltered science writing without the polemical posturing often encountered when non-scientists try to interpret what scientists are doing.

It was one of the most extraordinary achievements in the annals of biological science. Mr. Wilmut and his colleagues at the Roslin Institute in Scotland took a cell from the udder of an adult sheep, transplanted the nucleus into the egg cell from a second sheep, then inserted this into the uterus of a third sheep, and then into a fourth,to develop to term. Thus they were able to create a true clone of the original sheep. Achieving what many larger and better-known biology labs had failed to do, Dr. Wilmut, his team, and Dolly herself became instant world celebrities. Press and VIPs flocked to the Roslin Institute from all over the world, and Dolly developed into a shameless ham, posturing and posing for the cameras. And this was just the beginning. Megan and Morag followed – two sheep cloned from a partially differentiated embryonic cell, and then came Polly, a genetically altered sheep who was created to produce milk that contained a protein used to treat human hemophilia.

These remarkable developments are part of the explosion of progress in biological science now occurring at an ever-accelerating rate. Long the province of science fiction and fantasy, cloning and genetic alteration have finally emerged as established scientific facts. Nonetheless, the fantasy aura lingers. As Mr. Wilmut writes, “Fictional fascination with cloning has rarely focused on scientific fact but usually on issues of identity and how the sanctity of life will be challenged when ‘ditto machines’ of one kind or another create ‘cookie cutter humans.'” Think of Huxley’s “Brave New World,” for example. The result of this obsession is general confusion about what is possible and what is not. Mr. Wilmut believes that a calm discussion of the actual science is the necessary first step toward dealing with the moral and ethical considerations and here strives to clarify the scientific complexities.

There can be little doubt that these breakthroughs have tremendous potential to help in finding cures for heart disease, spinal cord injury, Parkinson’s disease, motor neuron (Lou Gehrig’s) disease, and Alzheimer’s. Although inalterably opposed to the cloning of human beings, Mr. Wilmut passionately believes that “by creating a cloned embryo of a patient, we can obtain a source of the patient’s own cells – stem cells – that can be used to understand the disease, test treatments, and not only repair a body but regenerate it too.” His conviction in the potential of these treatments is so great that he believes it would be immoral not to clone human embryos for such purposes. He is equally affirmative about the therapeutic possibilities of using embryonic cloning to prevent suffering caused by devastating hereditary diseases.In this application, doctors could correct defects in IVF-conceived embryos to create a new, healthy embryo that would then be transplanted to start a pregnancy.

This position does add up to a qualified proposal to clone and genetically alter, not replicate, human beings, which has aroused bitter opposition from people on both religious and ethical grounds. Mr. Wilmut acknowledges that many are opposed to any use of embryos for research or any proposal to alter human genes. This is where the potentials of science collide with moral opposition and spill out into the political arena. The virtue of Mr. Wilmut’s book lies in the extent to which he engages in this debate without demonizing his opposition or backing off from his own convictions. He takes great care to distinguish reproductive cloning from either therapeutic cloning or the use of cloning with genetic modification, and he is prepared to argue the question of the status of the human embryo. Is it a full version of life, or does it lie somewhere between the status of a cell and that of a person? What does it actually mean, he asks, when people condemn genetic research as unnatural? Indeed, what is life itself? A blastocyst, he argues, is not a person since it can only grow into a fetus or a baby with human assistance, and can thus be used for research without engaging religious opposition. The opposition could claim, however, that this is not a valid distinction, since neither a fetus nor a baby can grow without human assistance, either.

One could argue that the relentless expansion of knowledge, exemplified by Dolly and her scientific progeny, is exactly what makes us human. The future will always remain mysterious and open, but we cannot turn away from this quest now and “allow our fear of misuse of new knowledge to curb our exuberant creativity.” The final thought in this remarkable book sums up Mr. Wilmut’s passionate belief: “For me the widespread use of genetic and reproductive technologies is not a step backwards into darkness but a step forwards into the light. “The fundamental debate will doubtless rage on, and Ian Wilmut has made a powerful argument for a reasonable approach, both scientific and humane.

Mr. Pettus last wrote for these pages on the coming of age of the new biology.