THE AGE OF CLONING

Even now, a week after news of the achievement first flew around the globe, traces of astonishment linger in the air like a contrail. The landmark paper published late last week in the journal Nature confirmed what the headlines had been screaming for days: researchers at the Roslin Institute near Edinburgh, Scotland, had indeed pulled off what many experts thought might be a scientific impossibility. From a cell in an adult ewe's mammary gland, embryologist Ian Wilmut and his colleagues managed to create a frisky lamb named Dolly (with apologies to Ms. Parton), scoring an advance in reproductive technology as unsettling as it was startling. Unlike offspring produced in the usual fashion, Dolly does not merely take after her biological mother. She is a carbon copy, a laboratory counterfeit so exact that she is in essence her mother's identical twin.

What enabled the Scottish team to succeed where so many others have failed was a trick so ingenious, yet so simple, that any skilled laboratory technician should be able to master it--and therein lies both the beauty and the danger: once Wilmut and his colleagues figured out how to cross that biological barrier, they ensured that others would follow. And although the Roslin researchers had to struggle for more than 10 years to achieve their breakthrough, it took political and religious leaders around the world no time at all to grasp its import: if scientists can clone sheep, they can probably clone people too.

Without question, this exotic form of reproductive engineering could become an extremely useful tool. The ability to clone adult mammals, in particular, opens up myriad exciting possibilities, from propagating endangered animal species to producing replacement organs for transplant patients. Agriculture stands to benefit as well. Dairy farmers, for example, could clone their champion cows, making it possible to produce more milk from smaller herds. Sheep ranchers could do the same with their top lamb and wool producers.

But it's also easy to imagine the technology being misused, and as news from Roslin spread, apocalyptic scenarios proliferated. Journalists wrote seriously about the possibility of virgin births, resurrecting the dead and women giving birth to themselves. On the front page of the New York Times, a cell biologist from Washington University in St. Louis, Missouri, named Ursula Goodenough quipped that if cloning were perfected, "there'd be no need for men."

Scientists have long dreamed of doing what the Roslin team did. After all, if starfish and other invertebrates can practice asexual reproduction, why can't it be extended to the rest of the animal kingdom? In the 1980s, developmental biologists at what is now Allegheny University of the Health Sciences came tantalizingly close. From the red blood cells of an adult frog, they raised a crop of lively tadpoles. These tadpoles were impressive creatures, remembers University of Minnesota cell biologist Robert McKinnell, who followed the work closely. "They swam and ate and developed beautiful eyes and hind limbs," he says. But then, halfway through metamorphosis, they died.