  Molecular biology's technological capacity to manipulate the human genome brings society into something of an existentialist predicament. Science has tended to conceive human essence as a fixed object discoverable in nature. But a human essence embedded in manipulable genome is not immutable—it is created, not discovered. There is a very real sense in which in making the difficult choices we face—for example, those involved in prenatal genetic testing and germ-line manipulation—we really are choosing  ourselves.[20]