Toolkit Resources


The Two-Sex System: Fact or Fallacy? STIRS Student Case Study

Angela Bauer, PhD
Department of Biology, High Point University
High Point, North Carolina

Abstract:  This case study challenges students to consider the validity and fairness of society’s two-sex system (male vs. female), as they examine how this binary system continues to be perpetuated within the scientific and medical communities, even though it may not accurately reflect the variability that exists within the natural world. Students will learn about the six key factors (chromosomes, gonads, hormones, external genitalia, internal genitalia, and secondary sex characteristics) that contribute to one’s sexual phenotype, and then analyze data sets that illustrate the significant intra- and inter-sex variability that exists with respect to the expression of these key factors. Students will also learn about intersex conditions, their prevalence within the human population, and common approaches taken within the medical community to “normalize” intersex phenotypes, even though the frequency of intersex conditions is comparable to other unique phenotypes that our society accepts as “normal” (e.g., red hair, blue eyes). Next, students consider the life experiences of intersex individuals (through readings and a documentary), in order to identify the challenges they face living within the context of society’s binary system of sex/gender classification. Finally, students will engage in a debate on gender neutral housing on college campuses, an approach that addresses the inadequacies of traditional, sexed housing for those who don’t fit within the sex/gender binary, but introduces other factors into the learning environment that some consider problematic. This case study is based on actual events, with individual components of the case study classified as analysis cases (units 2-4), a directed case (unit 1), and a debate case (unit 5), according to the case categories of the National Center for Case Study Teaching in Science.

Use in Courses:  The case study is appropriate for a variety of courses, including lower level and general education courses (e.g., First Year Seminars; introductory biology, psychology, and gender studies courses; diversity courses) as well as upper level courses within a variety of majors (e.g., developmental biology, endocrinology, reproductive biology, human sexuality, psychology of gender, and various LGBTQ studies courses).  When incorporated into upper level courses, supplementary readings specific to the course of interest can be added to expound upon the material or ideas presented in the case study. For example, when used in a developmental biology course, the instructor could add additional reading materials that highlight other transcription factors (beyond Rspo-1 and SRY) that play a role in directing sexual differentiation (e.g., SF-1, SOX 9).

Of note is the fact that the activities included within this case study support High Impact Educational Practices as defined by the AAC&U (namely, educational practices that are known to foster a high level of engagement and thus enhance academic performance and retention).  For example, the exercises associated with units 1, 2, 3, and 5 are collaborative, student-centered assignments in which students work together in class to solve problems. Furthermore, the case study in its entirety addresses diversity issues in that the readings and documentary encourage students to explore life experiences that may differ from their own. This interdisciplinary case study also contains a writing intensive component (associated with unit 2), another high impact practice that benefits students at every stage of their undergraduate career. Finally, this case study would be an ideal component of high impact practices such as first year seminars and/or learning communities, particularly those that address diversity issues. Within the context of a learning community, the case study could serve as a springboard for other diversity-related extracurricular events, such as hosting a panel of speakers with diverse representations of sex and/or gender.

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Professor Bauer was named an AAC&U STIRS Scholar in 2014 and developed this case for the STIRS Program.