Should women and men compete in separate events in sports? And if they should, how do you decide who belongs to which category? Are there clear biological markers of sex?

This interactive explores the biology of sex determination and development in humans, set against the backdrop of the different sex testing policies implemented throughout sports history.

Version 1.0
Updated on 10/24/18



Laura Bonetta, PhD, HHMI
David Julian, PhD, University of Florida

Additional Writing and Research

Sandra Blumenrath, PhD, HHMI


Amy B Wisniewski, PhD, Cook Children's Pediatric Urology
Rebecca Jordan-Young, PhD, Barnard College
Ann Brokaw, Rocky River High School
Jamie Grimes, Walter Johnson High School
Jen Ramos, Baseball Prospectus prospect team & stats
Rachel Oltarzewski
Melissa Csikari, HHMI
Sydney Bergman, HHMI


Heather McDonald, PhD
Li Yao, HHMI


IdeaMACHINE Studio


Opening photo: Australian Associated Press
Photos of Dutee Chand and Ewa Klobukowska: Getty Images

Design and Development

kapow, inc.

Original Concept

The content is based on an original concept developed by Lydia Nussbaum, Dennis Liu, PhD, Judith Saks, and Donna Messersmith, PhD.