Fertilized cell

Despite over a decade of hype, cloning-based stem cell research has offered little in the way of scientific progress. It has been more symbol than substance; more moving target than realistic goal. However, by complicating both politics and policy, is has been a monkey wrench in the gears for progressive advocates of responsible biotechnologies.

Although there had been previous technological and policy developments in reproductive cloning, the 1996 birth of Dolly the Sheep - the first cloned mammal - catalyzed widespread concern and numerous laws about human reproductive cloning throughout the world. It quickly became clear that, outside of a handful of extreme techno-enthusiasts, reproductive human cloning had few defenders. Prohibitions in every nation, and even internationally, seemed to be just around the corner.

But two years after Dolly's birth, scientists led by James Thomson at the University of Wisconsin isolated human embryonic stem cells. These cells' power to differentiate into any tissue type - a characteristic called pluripotency - represented the foundation of a potential new type of medicine, in which cellular therapies could be used to repair the...