The 1990s brought you good-looking men with great, well proportioned facial features such stars such as Johnny Depp and Brad Pitt.Now, pretty boys such as Zac Efron and Chace Crawford are the sex symbols du jour. . . .It is not new that scientists have known that a woman's taste in men changes over her menstrual cycle.During the few days each month when women are fertile - the time of ovulation -