What constitutes biological sex, and how does it develop and differentiate? What implications arise from the categorization of sex? The Collaborative Research Center (CRC) investigates the diverse manifestations of physiological sex in different contexts. In an effort to explore this subject comprehensively, 17 distinct projects from biology, medicine, neuroscience, social sciences, and humanities are joining forces during the first funding period (2024-2027) of this research network. Employing an inter- and transdisciplinary approach, these projects consider the relevant levels of analysis of sex – ranging from cellular and organ levels to organisms, social systems, and epistemic cultures.

By characterizing the determinants, meanings and effects of sex on each of these levels, the CRC aims to gain a better understanding of sex in terms of biological and somatic differences. The research perspective goes beyond a purely binary model of sex and follows new scientific findings that show that sex is multifaceted and can manifest itself differently on several levels and in different contexts. These determinants and their interrelationships across all levels will be systematically examined.

The categorization of sex and the relationship between sex and gender are subjects of contentious debates. Recent research in both biological sciences and humanities has challenged assumptions about an exclusively binary and universalistic model of sex. The innovative research network thus explores the diversity, dynamics, and contextuality of sex. To avoid oversimplification, the CRC encourages reflection on frames of reference and the respective categorization of sex.

The CRC "sexdiversity" is focused on investigating the diversity of sex across various research contexts. Cutting-edge methods from biomedicine, natural sciences, humanities, and social sciences are employed – spanning from endocrinological and genetic laboratory research to clinical-medical studies and neuroscientific investigations, and extending to studies in the philosophy of science, as well as ethical, cultural, legal, and historical analyses.

The CRC brings together scientists, researchers, and clinicians from the University of Lübeck and the Christian-Albrechts-Universität zu Kiel. External experts from Berlin (Charité and Humboldt University), the European University of Flensburg, the University of Magdeburg, the Ludwig Maximilian University of Munich, and the Hannover Medical School, with expertise in research on differences of sex development (DSD), gender studies, and law, are also crucial contributors. Central to the CRC's organizational structure is the promotion and implementation of inter- and transdisciplinary research across life sciences, medicine, social sciences, cultural studies, and humanities. Our collective goal is to develop a more precise understanding of biological sex, comprehensively grasp sex diversity, advance new therapeutic methods for diverse patient groups, and actively involve individuals with DSD, activists, and stakeholders in the research process.

An improved, empirical understanding of sex and sex diversity will lay a more robust foundation for personalized medicine and innovative clinical treatments. Contributions from the humanities and social sciences will not only refine our understanding of the interplay between sex and gender, but also promote methodological reflexivity in research processes and elucidate essential legal and ethical principles.