After introducing several new elements into an introductory mechanics course for life science students, we observed a substantial reduction in the gender gap on the Force Concept Inventory (FCI). Among those students with the strongest scientific reasoning abilities, where previously the gender gap had been largest, the gender gap was completely eliminated. The course used the Thinking in Physics curriculum, an interactive engagement pedagogy aimed at developing general thinking and problem solving skills along with an understanding of physics. The new elements, designed to reduce stereotype threat and to improve the experience of female students, included giving students a self-affirmation writing exercise created by researchers at the University of Colorado, providing a learning guide, and assessing and interviewing students at the beginning of the course.