Dear Sen. Lankford,

There’s been a considerable amount of news lately over the question of what defines a woman. You and others have indicated that the answer to this question is simple, with the implication that anyone who hesitates to define “woman” is either undereducated or delusional.

Well, this letter is coming to you from faculty members at the University of Oklahoma who teach anatomy and physiology. We hope we are offering a perspective that is both educated and grounded in reality when we state that a single, simple definition for “woman” is not tenable.

Take, for example, Madison Cawthorn’s definition of a woman (“XX chromosomes, no tallywacker”). Although it scores points for simplicity, this definition would not apply well to everyone. About 1.7% of people are intersex (according to "Sexing the Body" by Anne Fausto-Sterling), which means that their genitals are in between typically male and typically female and/or they have a mismatch between their chromosomes, gonads, and/or genitals (if you would like to acquaint yourself with one of these people, check out Emily Quinn’s TED talks).

Moreover, there is now evidence (see Neuroscience and Behavioral Reviews, Vol 122: pg. 165-175) that most people's brains have some physical features that are more typically female and others that are more typically male, regardless of whether they consider themselves women, men or nonbinary, and regardless of whether they are cisgender or transgender. If our brains largely define who we are, and our brains are not binary, then defining “woman” is a tricky proposition.

Presumably, the primary targets of the “define woman” rhetoric are people who are transgender, nonbinary or intersex — i.e., those who may be psychologically aligned with a gender that does not agree with the sex assigned to them at birth.

Many seek to undermine the legitimacy of these people by claiming that their identity is somehow a rejection of the science of biology, but this claim is misguided. As biologists we try to shed light on complexity and variation, not to limit what is socially acceptable with regard to gender roles. We think that we speak for the vast majority of experts on human biology when we say that science DOES NOT support the rejection of transgender or nonbinary people, nor does it warrant any objection to them presenting their preferred gender in our society.

In her confirmation hearing, Justice Ketanji Brown Jackson shied away from defining “woman,” stating, “I’m not a biologist.” We want to make it clear that an adequate definition is not so easy for professional biologists either.


A. Bentz, A. Berkowitz, E. Bridge, C. Gordon, H. Ketchum, and K. Willis,

Faculty in the Department of Biology and Oklahoma Biological Survey at the University of Oklahoma


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