In less than two generations, a seismic shift has occurred in the makeup of the American family. Today,fatherlessness has become the norm for about forty percent of American children and, some experts believe, contributes to some of our most urgent social problems. FRONTLINE explores this dramatic change in the American family and the startling findings of sociologists that, despite economic status, children from single parent homes are twice as likely to drop out of high school, to become teen-age mothers, and to spend time in jail.