What is sex?

There are many ways to parse the biological meaning of “sex,” as we will review below. I am mostly interested in the legal meaning, however, because it affects social rights and status. I have traced the legal definition of “sex” back to the notorious Dr. John Money of David Reimer fame. Yes, indeed.

I found a FOOTNOTE in the law review article Transsexuals in Limbo: The Search for a Legal Definition of Sex  31 Md. L. Rev. 236, 237 (1971) that reports as follows:
10.  Money  lists  seven  variables  which  interact  to  produce  the  ultimate  sex  of  the individual:
  1. Chromosomal  – fertilization  and  early  zygotic  proliferation  as  either  a 46/XX  female  or  a  46/XY  male,  that  is  a  sex  chromatin-positive  or -negative  respectively.
  2. Gonadal  – differentiation  of  the  primitive  gonadal  ridge  into  either  an ovary  or  a  testis.
  3. Hormonal  – differentiation  of  hormonal  function  (a)  in  the  fetus  to  produce  feminine  or  masculine  organizer  substances,  and  (b)  at  puberty  to produce  either  feminine  or  masculine  secondary  sexual  characteristics.
  4. Internal  morphological  – differentiation  of  either  the  mfillerian  or  the mesonephric  (wolffian)  duct  into  the  internal  accessory  organs  of  reproduction.
  5. External  morphological  – differentiation  of  the  external  genital  anlagen into  either  female  or  male  sex  organs.
  6. Assignmental  – assignment  of  sex  at  birth  as  either  female  or  male,  with subsequent  experiences  of  rearing  reinforcing  this  decision.
  7. Psychosexual  – differentiation  after  birth  of  a  psychosexual  identity  as either  female  or  male.
Money,  The  Sex  Chromatin  and  Psycholosexual  Differentiation,  in  THE  SEX  CHROMATIN  434-35  (K.  Moore  ed.  1966)


This list of “variables” is repeated in various judicial opinons and legal briefs affecting the status of transsexual people. Here are two examples.

From a petition filed in NYC (Berkley v. Farley) that challenges the surgical sex-change requirement for birth certificate revisions:

7. In those forty years, the medical, scientific, legal, and psychological understandings of trans gender persons have progressed substantially. The mainstream view of these communities no longer equates sex with chromosomes or genitalia alone. Rather, it is now accepted that a person’s sex is determined by a host of factors, including
(4) chromosomes,
(3) gonads (ovaries or testes),
(5) hormonal secretions,
(1) internal reproductive organs,
(2) external genitalia,
(6) secondary sexual characteristics, and
(7) the brain sex or one’s self-identified sex.

Bold, numbers, and line spacing have been added to show consistency with the 2003 decision of The Court of Appeals in Maryland In re: Heilig (see page 8).

There is a recognized medical viewpoint that gender is not determined by any single criterion, but that the following seven factors may be relevant:

(1) Internal morphologic sex (seminal vesicles/prostate or vagina/uterus/fallopian tubes);
(2) External morphologic sex (genitalia);
(3) Gonadal sex (testes or ovaries);
(4) Chromosomal sex (presence or absence of Y chromosome);
(5) Hormonal sex (predominance of androgens or estrogens);
(6) Phenotypic sex (secondary sex characteristics, e.g. facial hair, breasts, body type); and
(7) Personal sexual identity.

Bold added to the terms medical and gender. Interestingly, the Berkley petition seeks to prove sex, while Heilig cites gender. It is an excellent illustration of the legal mess created by using the word “gender” as interchangable with “sex.”

Of these seven factors, all but ONE refer to objectively demonstrable physical criteria. Using “gender identity” legislation, trans activists argue that the single subjective factor on the list (#7) should override the other six variables. Here is a typical example of a “gender identity” definition:

“Gender identity” means a gender-related identity, appearance, expression, or behavior of an individual, regardless of the individual’s assigned sex at birth.

I repeat, “regardless of the individual’s assigned sex at birth.

As a human born into a female body and  socially assigned the girl/woman sex-role at birth, I am opposed to the replacement of legal “sex” with any kind of subjectively asserted identity, appearance, expression, and/or behavior. “Sex” is not an identity or a choice. Sex is a bodily reality.

No single factor can or should be dispositive of an individual’s sex. Evidence of secondary sex characteristics (6) is generally accepted as proof of an individual’s “sex” despite the fact that these physical markers can be constructed and/or modified through medical interventions. Factors (2), (5), and (6)–genitals, hormones, and secondary sex characteristics–are also medically malleable. As a result, one or more of them often serve as the only legally necessary proof that a person’s sex has changed from the one assigned to them at birth.

By contrast, chromosomes (4) are immutable. Factors (1)  and (3)–internal morphologic sex (seminal vesicles/prostate or vagina/uterus/fallopian tubes) and gonadal sex (testes or ovaries)–are also immutable. They can be removed from the body but medical technology is not able to construct functional facsimiles of them. Either you’re born with these reproductive organs or you are not.

The biological purpose of these “sex” organs is clearly human reproduction.

From monthly menstruation to fetal gestation, female bodies bear the primary burden of human reproductive processes. This existential reality is not under human control. Recognizing this, therefore, we should use the physical manifestations of female reproductive processes as the lens through which we establish the legal meaning and substance of “sex.” Female bodies and perspectives should be the default, not males’.


  1. As usual, excellent analysis.

    Here’s my two cents worth:

    #6 and 7 need to be rewritten – at birth there is only visual identification – kind of like people who look at silhouette of aircraft in the sky, and identify a Cessna, B-52, drone…the visual identification does not “interact” with the other (prior) variables “to produce the ultimate” type of aircraft – that all took place in the factory.

    #7 repeats #6’s “subsequent experiences of rearing reinforcing this decision” in different language. And I think “psychosexual” is actually “psychosocial.” He’s using the wrong term.

    Just need to leave 6 and 7 off completely – I think in #7 he’s trying to shoehorn gender into things.

    I also like the idea of “thought experiments,” to tease out the plasticity of gender and the inflexibility (immutability) of biological sex. For instance, imagine a woman married to a soldier who died in one of the Iraq wars. She has an infant son when her husband dies. Her late husband loved pink, because he was born and raised in Florida, he loved the wild pink sunsets and the big conch shells (pearlescent pink on inside). So, in honor of her late husband, she paints her infant son’s room PINK, and goes with a Florida seaside theme (lots of seashells). As her son grows up, she tells him about his father, his love of Florida, his service to his country.

    So the son grows up loving pink, PROUD OF PINK, he wears pink clothing to school. He also wears nail polish, has long hair, loves to cook (his dad was something of a gourmet). He has no problem with pink, has no problem handling other kids’ teasing OR bullying (he studies martial arts and kicked the books out of one of his bullies’ hands).

    This kid is not in conflict about his sexuality (I leave unspecified), his biological sex, OR his gender. Thought experiment: Well, WHAT is this kid? Let’s say he’s elected homecoming king, and wears a pink tux to prom. Well, what is he? In the current atmosphere around trans, how do the majority of teachers and students respond to him? How do male students who “identify” as female respond to this student? Does his example make it easier for “non-gender-conforming” male students to resist pressure to “transition?” Do they pressure him?

  2. “6. Assignmental – assignment of sex at birth as either female or male, with subsequent experiences of rearing reinforcing this decision.”

    I wanted to add some anecdotal evidence – when I was in high school, I had a math teacher who told us he was the biggest sexist, he thought women should just be homemakers (nothing wrong with homemaking, it is a perfectly acceptable life path for anyone). Well, he WAS the biggest sexist…until he had daughters…and only daughters. Then, he said, he became the biggest women’s libber (it was a while ago), because he wanted his daughters to accomplish anything in life they wanted to.

    So this idea of a lock-step A) assignment of gender at birth and then B) “subsequent experiences of rearing reinforcing this decision,” does not correlate with objective, testable reality. While children are being reared, they can (and do) “rear back,” changing the gender assumptions of the parent; or, as with my math teacher, the sheer fact of having an unexpected “gender distribution” in offspring can alter the kind of gender-rearing a child receives.

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