Ian Wilmut

In an unprecedented feat, Scottish scientists have cloned an adult mammal by inserting DNA from a single sheep cell into an egg, implanting it in a surrogate mother and raising it to adulthood. They now have a healthy, 7-month-old sheep named Dolly--an exact genetic duplicate of the animal from which the single cell was taken. Six other clones have been produced using the same technique.

When researchers announced the first successful cloning of an adult mammal, they took a major and, by some reckonings, a troubling step in the science of sex by breaking one of nature's basic biological taboos, scientists and medical ethicists said Sunday. The innovation opens the door on to a "Blade Runner" world of human replicants and customized animal clones.

Occasionally, a great change in history comes about quickly and without warning, transforming the very way we perceive ourselves and the world around us for generations to come. Such was the case when the world first heard about Dolly the cloned sheep. Now, Ian Wilmut, the Scottish scientist who cloned Dolly, has made history a second time, and the new development is likely to have an even greater impact on the world than the first.

As teenagers about to graduate from high school many years ago, a friend and I were allowed to stand righteously at the pulpit before our church congregation and rave on about our elders' mishandling of current events. Their failures--racism, the Vietnam War, the flammability of the Cuyahoga River--were egregious and reflected basic human defects, we opined. Our solution? Change human nature. It seemed like a good idea at the time.

If quality of life for an aging population can be improved through genetic manipulation, then the man of the hour is embryologist Bill Ritchie. The featured speaker at a recent soiree, Ritchie was a clutch member of Dr. Ian Wilmut's Roslin Institute in Edinburgh, Scotland, which spliced together the chromosomes that, in 1997, resulted in Dolly, the first cloned sheep.

Two scientists who upended fundamental beliefs about biology by demonstrating that every cell in the body has the potential to grow into every other type of cell have won the Nobel Prize in physiology or medicine. Sir John Gurdon and Dr. Shinya Yamanaka were honored Monday for "the discovery that mature cells can be reprogrammed" to return to a very early state of development, the Nobel committee said in its citation. Their research is still years away from yielding a clear breakthrough in medical treatment.

After years of false starts and an international scientific scandal, researchers said Wednesday that they had achieved a feat that some scientists believed was impossible -- cloning a monkey embryo from a skin cell of an adult and using it to harvest embryonic stem cells. Scientists have previously cloned embryos and adult animals of a variety of species, including rats, dogs and cattle. But primates -- the family that includes monkeys and humans -- have proved remarkably resistant to the most sophisticated techniques in the cloner's arsenal.

An instinct by humans to protect their distinctiveness is evident in the first responses to the announcement that a scientist in Scotland has cloned an adult sheep. The biologist Ian Wilmut and the sheep Dolly have become instantly familiar figures. At once, respondents to the news speculated about human cloning. Not "whether" the technique will be applied to humans but "when" and "what then" have framed most questions. Guarding what is left of human distinctiveness has to be at issue.

I'm very upset. It seems Dolly may have been a fraud. You remember Dolly, don't you? The cloned sheep who gave headline writers all around the world such a heyday this time last year? Now it seems that Dolly's cloning might be just another Scottish myth, like Brigadoon. This past month at a geneticists' forum in Louisville, Ky.