Little Lamb, Who Made Thee?

KEITH CAMPBELL WASN'T THINKING, REALLY, ABOUT ROOMS full of human clones, silently growing spare parts for the person from whom they had been copied. Nor was he thinking about giving lesbians a way to bear a biological descendant without visiting the sperm bank. And he certainly wasn't aiming to give pro-team owners a tool to copy their greatest players, hospitals their best doctors or parents their dying child. Campbell, a cell biologist at the Roslin Institute in Scotland, was thinking... sheep. Lots of sheep, hillock upon hillock of sheep, enough sheep (given enough fences) to put all the insomniacs in Scotland to sleep. And all produced from a single cell of a single ewe.

Cloned.

Campbell knew that cloning from an adult mammal was, according to every textbook, impossible. He knew that once a cell has decided what it's going to be when it grows up--part of bone, nerve, skin or any other organ-it is like a CD album that will play only a single track. Although every cell in every body, from liver cells in a person to udder cells in a sheep, contains the complete genetic blueprint for making the entire person or the entire sheep, only the genetic melody for the liver cell or the udder cell is actually played. Dr. Ian Wilmut, in his Roslin Institute lab, was just looking to build a better glass of milk--containing medicine for premature babies The other tracks--instructions for the complete organism--have been silenced. But Campbell would have none of that. He and his Roslin colleagues were going to clone a lamb from an adult cell. Even though everyone said it couldn't be done.

At Roslin they stopped saying that in February 1995, after Campbell strode down the hall to the professorially messy office of his colleague Ian Wilmut. He had figured out, he told Wilmut, how to get adult cells to sound each and every one of the genetic notes required to make a complete animal. The key was to make the cell "quiescent," or inactive. In that state, all of its genes have the potential of being played, Campbell realized. All that was needed was the player. And Campbell had just the thing: a sheep oocyte--egg cell-contains special proteins that turn on genes, playing all the tracks, one after another, like the laser beam in a CD player. "We have to be very quiet about it," Campbell told Wilmut. "We can't tell anybody." And he didn't, until last week, when the world learned of the arrival of Dolly, born last July, the first mammal cloned from an adult cell.

Cloning--manipulating a cell from an animal so that it grows into an exact duplicate of that animal--is the forbidden fruit of biotechnology. Some scientists were so sure it could not be done that, in the 1970s, they dissuaded bioethicists from pondering its moral implications. Yet at the same time other scientists, in out-of-the-way labs and under the cloak of secrecy, were getting ever closer to making clones. What cloning is not, despite all the professions of surprise in the wake of Dolly's birth announcement last week, is unexpected. For 10 years scientists have been cloning sheep and cows from embryo, though not adult, cells. And the research hasn't stopped with the beasts of the field. In 1993, embryologists at George Washington University cloned human embryos: they took cells from 17 human embryos (defective ones that an infertility clinic was going to discard), all two to eight cells in size. They teased apart the cells, grew each one in a lab dish and got a few 32-cell embryos-a size that could be implanted in a woman (though they weren't). So scientists' professed surprise over Dolly rings somewhat hollow.

The real question, of course, was, wherever the lamb went, was Mary sure to follow? In other words, how soon will scientists clone humans? Nature, the scientific journal that published the Dolly paper, editorialized, "Cloning humans from adults' tissues is likely to be achievable any time from one to ten years from now." Cornell University biologist W. Bruce Currie estimates that only 10 labs in the world (his not among them) can manipulate sheep cells the way Dolly's makers did, getting them to become quiescent and producing clones from them. But in principle "there is no difficulty at all in driving human cells I'm a lab dish] into [quiescence]," says Currie. "All that's needed is to take a culture of proliferating cells and deprive them of [nutrients]." Last week, as scientists cast about, almost desperately, for an obstacle to human cloning, embryologist Colin Stewart of the National Cancer Institute came up with one. In sheep embryos, the genes from the donor cell do not turn on until the egg has divided three or four times, he pointed out, In humans, those genes turn on after two divisions. That difference might be an insurmountable obstacle to human cloning-or it might not. But on the more profound question of what, exactly, a human clone would be, doubters and believers are unanimous. A human clone might resemble, superficially, the individual from whom it was made. But it would differ dramatically in the traits that define an individual--personality and character, intelligence and talents. "Here's the rule," says psychologist Jerome Kagan of Harvard. "You will never get 100 percent identity-never--because of chance factors and because environments are never exactly the same."