Age and gender are among the simplest and most visible social markers in human interaction, but among the most complex and puzzling variables with which social scientists deal. Theoretical and empirical treatment of the variable of “age” has become more sophisticated than treatment of the variable of “gender.” A test of a sociological interpretation of sex or gender differences would require us to develop sociological measures of what is meant by the social construction of gender, and to demonstrate that with controls for these sociological measures, the original sex difference disappears. A bioevolutionary approach sensitizes us to the special significance of gender. Several design characteristics flowed from the three foci on gender, life course, and relationship perspective. To minimize any tendency to link certain types of help to gender, examples were given to project the item’s relevance to both mothers and fathers, or sons and daughters. The chapter also presents an overview of the key concepts discussed in this book.