Is a loved one missing some body parts? Are blondes becoming extinct? Is everyone at your dinner table of the same species? Humans and chimpanzees differ in only 400 genes; is that why a chimp fetus resembles a human being? And should that worry us? There's a new genetic cure for drug addiction; is it worse than the disease? We live in a time of momentous scientific leaps, a time when it's possible to sell our eggs and sperm online for thousands of dollars and to test our spouses for genetic maladies.