Last May, a stunning research paper in Science, one of the world's most respected scientific journals, instantly changed the tenor of the debate over cloning human embryos and extracting their stem cells. A team of South Korean scientists reported in the paper that they had figured out how to do this work so efficiently that the great hope of researchers and patients - to obtain stem cells that were an exact match of a patient's - seemed easily within sight. But that rosy future has been cast into doubt with the statement last month by Dr. Hwang Woo Suk, who...