Cloning, stem cell research and some historic parallels.

Too many scientists have called for "therapeutic" cloning, and for use of the "spare" embryos, without thinking through the several consequences, some of which could be devastating. For example, Humpherys, et al., have shown in mice that cloning by nuclear transfer is so inefficient that most clones die. Those that survive often display growth abnormalities. They also examined the embryonic stem cells and found their genome to be "extremely unstable".