Book review of Gregory Stock, Redesigning Humans: Our Inevitable Genetic Future.

GREGORY STOCK has written an enthusiastic book in support of germ-line manipulations -- that is, making genetic modifications to eggs, sperm and embryos that can be passed on to future generations. Like previous explorations of the subject by the ethicist Joseph F. Fletcher, the lawyer John Robertson and the biologist James Watson, among others, ''Redesigning Humans: Our Inevitable Genetic Future'' serves as an apologia for those scientists and physicians who are already edging toward such work in a piecemeal fashion in research labs and in vitro fertilization clinics around the world. It advocates the wholesale adoption of genetic manipulations with the purpose of finally taking control of human evolution. This, the author writes, ''is the ultimate expression and realization of our humanity.''

Because of the breadth of his scientific knowledge and his considerable flair as a writer, Stock -- who heads the program on medicine, technology and society at the School of Medicine of the University of California, Los Angeles -- is a forceful advocate. First and foremost,...