CGS-authored

Ten years ago this month, a ewe at a quiet research facility just outside Edinburgh, Scotland, gave birth to a lamb, known then as 6LL3. Seven months later, 6LL3 stepped onto the international stage with a more personable name as the most famous sheep of all time: Dolly, the first cloned mammal. She was the product of inserting a cell from an adult sheep's udder into a sheep egg from which the nucleus had been removed, then placing it in a ewe to develop.

Dolly changed the public's idea of what biotechnology might do and immediately posed the question: Can human clones be far behind?

"Dolly was important as a symbol of science gone out of control," says Arthur Caplan, director of the Center for Bioethics at the University of Pennsylvania. "People were very afraid of cloning and what it might mean in terms of genetic engineering."

A decade later, those concerns and speculations have cooled. Cloning, it turns out, is a difficult proposition. Dolly was the sole survivor among 277 attempts to clone a sheep. Human cloning has proved...