“The way bioethics works is that all the questions of right and wrong aren’t always all up for grabs at the same time.”  —Arthur Caplan, New York Times Magazine, December 15, 1996.

Much of the world was in shock when Ian Wilmut and his colleagues announced in February 1997 that they had taken a cell from a ewe’s udder and cloned a sheep named Dolly. After reviewing the issue, the National Bioethics Advisory Commission recommended a five-year moratorium on human cloning in the United States to allow further study of cloning technology and ethics. A few months later, in December 1997, Wilmut’s lab in Scotland announced that they had cloned two more sheep, Molly and Polly, this time with human blood-clotting proteins in their milk. The proteins will be extracted from the milk and used to treat human hemophilia. Wilmut’s...