In February 2004, Woo--Suk Hwang made world headlines when he claimed to have cloned human embryos using a technique called somatic cell nuclear transfer, and then to have derived a line of stem cells from the embryos that could be used for medical research. Enthusiasm for this first "successful" experiment in human cloning, published in the prestigious peer--reviewed journal Science, was tempered by the inefficiency of the process: It took 242 human eggs to get just one embryonic stem cell line.That problem seemed solved when, last May, Hwang published another article in Science asserting that he had again successfully...
