The emerging phenomenon of genetic paternity testing shows how good science and useful social reform can run off the rails. Genetic paternity testing enables us to sort out, in a transparent and decisive way, the age-old but traditionally never-quite-answerable question of whether a child is genetically related to the husband of the child's mother. Given the impossibility of settling this question for certain, British and American law has long held that a biological relationship must almost always be assumed to exist. (...) According to what is known as the “marital presumption” or “presumption of legitimacy,” a child born to a woman within a marital relationship is assumed to be the biological child of the woman's husband unless he was absent, impotent, or sterile. In other words, if paternity was not a physical impossibility for the husband, there was a nearly irrebuttable presumption that he was the father of the child. The husband was locked into the role of fatherhood. a. (shrink)