Cloning Gets Closer

Back when it was no more than a cheesy science-fiction plot device, human cloning seemed like something that would eventually be revealed to a horrified world full-blown and fully grown--a monstrous carnival apparition ("The Amazing Cloned Boy!") out of a medical freak show.

It hasn't quite turned out that way. Cloning has been emerging gradually, over the past decade, in small increments. Each advance has been startling enough, prompting ethical debates, cautionary references to Aldous Huxley's brave new world and calls for restrictive legislation. But there have been so many milestones, starting even before the birth of Dolly the sheep in 1996, that each one seems a little less startling than the one before. Sometimes an advance is so subtle that it sounds just like the breakthrough that made headlines the year before.

That's how a report in the journal Science sounded last week--at least at first blush. Woo Suk Hwang and Dr. Shin Yong Moon, from Korea's Seoul National University, announced that they had created more than 200 embryos by cloning mature human cells and had grown 30 of them to the blastocyst stage of development, each more than 100 cells strong. This isn't the first time cloned human embryos have been produced: in 2001 the Massachusetts biotech firm Advanced Cell Technology made several. They all died quickly, but in a sense the first cloned human cells are actually old news.

Still, two things make the Korean experiment more than a little noteworthy. The first is simply that their embryos didn't die. That's a very big deal; many experts were convinced that human clones would be impossibly fragile. Second, the scientists extracted embryonic stem cells from the blastocysts and coaxed some of them into a self-perpetuating colony.

That could ultimately prove to be an even bigger deal. Embryonic stem cells are the unspecialized raw material that give rise to every cell type in the body--in fact, some of Moon and Hwang's stem cells evidently turned into bone, muscle and immature brain cells. If scientists can learn to control their development, stem cells could in theory supply replacement tissues to treat any ailment involving cell damage--and there are plenty, including heart disease, diabetes, spinal-cord injury, Parkinson's and Alzheimer's. "Our goal," said Hwang during a press conference at a meeting of the American Association for the Advancement of Science in Seattle last week, "is not to clone humans, but to understand the causes of diseases."

That disclaimer didn't satisfy critics. Indeed, the Korean breakthrough adds fuel to two different ethical debates at once. The first--whether cloning for reproduction should be allowed--is pretty well settled. Only a handful of loose-cannon scientists and members of the Raelian sect, who believe humans were created by aliens, openly favor human cloning. It is explicitly banned in many countries, including Korea.