“Most people, I suspect, regard genetic engineering as something that will happen tomorrow,” writes science journalist Charles C. Mann in a 1998 article. “They are wrong. Biotechnology is here today.” In 1973, geneticists announced that they had spliced a gene from a toad into a bacterium, creating the first “transgenic” organism. Since then scientists and researchers have made remarkable and rapid progress in manipulating genes—the basic biochemical building blocks that govern all life forms. By the end of the twentieth century more than 4,600 genetically modified organisms—most developed for agricultural purposes—had been field-tested; and genetically engineered tomatoes, potatoes, and other foods had found their way to American supermarkets. The amount of U.S. farmland planted with genetically modified seeds grew from 6 million acres in 1996 to 58 million in 1998. Bacteria have been genetically...