If you put your ear to the tracks, you can hear the train coming.
In conference halls around the world, geneticists and developmental biologists have been gathering to discuss what once was unthinkable-genetically engineering human embryos so that they, and their children, and their children's children, are irrevocably changed. These experts are talking with remarkable candour about using germ-line engineering to cure fatal diseases or even to create designer babies that will be stronger, smarter, or more resistant to infections.
Doctors are already experimenting with gene therapy, in which a relatively small number of cells-in the lungs, say-are altered to correct a disease. Germ-line engineering, however, would change every cell in the body. People would no longer have to make do with haphazard combinations of their parent's genes. Instead, genetic engineers could eliminate defective genes, change existing ones or even add a few extra. Humanity would, in effect, take control of its own evolution.
So awesome is this idea, that until a year or so ago, the taboo on human germ-line engineering was absolute. But opinions have started to shift....