We are living through a time of enormous cultural change involving broad reconsideration of ideas about individual sex and gender, their boundaries, their meanings, and their mutabilities. There is a growing realization of the diversity of lived gender identities and sexual experiences. In many cultures, an ever-larger number of people are declaring transgender, nonbinary, gay, lesbian, bisexual, and other nonnormative identities and orientations. 

These cultural changes have not gone unopposed. Having lost the legal battles in the United States to prevent marriage equality and protections against sexual discrimination in the workplace, political and religious conservatives have mounted a new wave of efforts to legally enforce strictly binary definitions of sex and gender in the United States. Under the Trump administration, the United States Department of Health and Human Services adopted a new federal definition of individual sex as “unchangeable and determined on a biologic basis.” New federal rules established that “sex means a person’s status as male or female based on immutable biological traits identifiable by or before birth,” and that “the sex listed on a person’s birth certificate, as originally issued, shall constitute definitive proof of a person’s sex unless rebutted by reliable genetic evidence.”1 This legal change eliminated federal recognition of the over 1.4 million transgender Americans, which could have dramatic impact on their access to health care, legal protections, and civil protections in schools, jails, shelters, and other public institutions. This legal definition of sex has since been rescinded by the Biden administration, but the political challenges continue. 

In 2020, Idaho became the first US state to permanently define an individual’s sex as the sex on their birth certificate, and to prevent transgender girls from participating in scholastic sports.2 Since 2021, a tsunami of state legislation defining sex as a binary fact established at birth, prohibiting transgender girls from participating in sports, and restricting or prohibiting medical treatments for transgender minors have been proposed or adopted in dozens of American states. In February 2022, the Texas governor instructed the Texas Department of Family and Protective Services to say that gender-affirming medical treatments, including puberty-blocking drugs and hormone therapies, constitute child abuse under Texas law. These political efforts to constrain the rights of transgender youth, transgender adults, and their families are moving so fast that it is impossible to accurately summarize them here. 

In February 2021, in response to a trans pride flag hung across the hallway outside the office of another congresswoman, Marjorie Taylor Greene, the Republican representative of Georgia’s Fourteenth Congressional District, placed a large sign outside her office door in the United States Capital building stating: There are only TWO Genders: MALE & FEMALE “Trust the Science!”. 

Putting aside Greene’s refusal to trust the science on global climate change, evolution, the prevention of gun violence, vaccination, epidemiology, and a host of other vital issues, we have to ask ourselves, “To what science is Greene referring?” What is science communicating to the public about sex and gender that gives Greene the impression that science unequivocally supports her views?