With a title alluding to the complicated past of gender and sex, Mary P. Ryan's Mysteries of Sex: Tracing Women and Men through American History gives us a thoughtful and thorough examination of the long debated battle over the differences between men and women. The question of how the dividing line between male and female is drawn—and repeatedly redrawn—over the course of history is still at the forefront of gender issues, and Ryan attempts to lay out practical guidelines for the reader in order to navigate through the many historical possibilities of what makes a...