Myths/Humans cannot change sex

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Myth: Humans cannot change sex.


This claim has been expressed in a number of different ways:

  • You cannot change your sex.[1][2]
  • Human biological sex is immutable.[3]
  • You cannot change your gender.
  • Sex isn't "assigned" at birth.[1]

It is typically used as an argument against:

  • the idea that trans people are genuinely the gender they say they are
    • ...and therefore against the idea that they deserve access to spaces and privileges of their gender identity rather than their birth-assigned gender...
      • especially female spaces/privileges, most notably:
      • access to women's bathrooms
      • competing athletically as women
  • sex reassignment surgery (funding it, allowing access to it, and/or providing it[4])


These claims tend to ignore or dismiss several decades of scientific discovery in the understanding of sex and gender, while others try to blur the lines between sex and gender. In general, they also focus on one aspect of sex while ignoring the reason that people seek SRS.

  • "You cannot change your sex." -- this is an ambiguous statement open to multiple interpretations:
    • If "your sex" is defined as...
      • "your biological role in reproduction" (as one myth-source article[1] defines it), then you certainly can do so by means of any operation that renders one sterile. Sterilization is not, however, the only reason transgender people seek SRS; if it were, then mere removal of the gonads (or vasectomy, for male bodies) would suffice.
      • something else, then what is that?
    • If "change" means "reverse" (rather than "in some way alter"), then trans people are certainly not seeking SRS for that reason, as medical technology does not yet permit the transformation of a reproductively-male body into a reproductively-female body, although current progress makes it likely that this will be possible in a matter of decades at most. (One feels compelled to wonder if anti-SRS advocates will stop raising this objection once that happens.)
  • "Human biological sex is immutable" is either defining "biological sex" to specifically mean reproductive role, or else is conflating the many aspects of biological sex into one and claiming that none of them can be changed, which is patently false. (See also: biological sex)
  • "You cannot change your gender" is true as stated, and indeed is a fundamental basis of how gender identity works. When transgender people transition, however, they are not attempting to change their gender. They are attempting to alter their body's physical gender (primary and secondary sexual characteristics) to match their gender[5]. Again we come to the question of "why does it matter if this is true?"
    • Worse, there's often an implication that a (trans) person whose physical gender is A but who identifies as B is "changing their gender" to B -- when in fact it has been B all along; see gender identity.
  • "Sex isn't "assigned" at birth." may be true, depending on what you mean by "assigned"; see sex assignment.

Blurring the lines

  • "You cannot change your sex" is ambiguous in at least a couple of ways, either implying an outright falsehood or implying that SRS has a particular goal which it does not actually have.
  • "You cannot change your gender" blurs the lines between "sex" and "gender": trans people are not attempting to "change gender", so why argue that it can't be done?
  • "Sex isn't "assigned" at birth" is either true and undisputed, if "assigned" means "chosen arbitrarily", or else plainly false if "assigned" means "determined from the physical evidence". The meaning of "assigned" is being blurred here.

Issue Unclear

  • "You cannot change your sex", if taken to mean "you cannot convert a body from one reproductive role to the other", is certainly true within the limits of current medical technology.
  • "You cannot change your gender" states a truth that trans advocates strongly support. (If gender could be changed, then transition would probably be unnecessary.)

If these are the intended interpretations, trans advocates do not dispute them – so why state them except as straw man arguments? If these are not the intended interpretations, then how were they supposed to be interpreted? Either way, they should be stated less ambiguously.

Moving Goalposts

  • "Human biological sex is immutable" is a retreat from the older position that biological sex itself is immutable[2], which is flatly contradicted by the existence of a number of animal species which change their reproductive functioning over a normal lifetime.

Further Reading


  1. 1.0 1.1 1.2 2018/03/05 Sex Change Physically Impossible Psychosocially Unhelpful and Philosophically Misguided:
    • "sex isn’t 'assigned' at birth – and that’s why it can't be 'reassigned.'"
    • "Cosmetic surgery and cross-sex hormones can’t change us into the opposite sex. [..] They can’t turn us from one sex into the other."
    • "transgender men are not biological men and transgender women are not biological women." (quoting Dr. Lawrence Mayer)
    • "Changing sexes is a metaphysical impossibility because it is a biological impossibility." (quoting philosopher Robert P. George)
    • "Transgendered men do not become women, nor do transgendered women become men." (quoting Paul McHugh)
  2. 2.0 2.1 2019/12/18 Judge rules against researcher who lost job over transgender tweets quotes Maya Forstater: "My belief [...] is that sex is a biological fact, and is immutable. There are two sexes, male and female. Men and boys are male. Women and girls are female. It is impossible to change sex. These were until very recently understood as basic facts of life by almost everyone."
  3. Note that this is a steel manned version of the claim, which is sometimes phrased as "mammals cannot change sex" (same problem in definition, and also why are mammals special, if not purely for cherry picking?) or even "sex is immutable", which is obviously wrong in that there are many species of animal which do change sex as part of their natural life-cycle. See for example the questionably-titled 11 Animals That Can Change Their Gender
  4. 2004/11 Surgical Sex: Why We Stopped Doing Sex Change Operations
  5. or, more precisely, to match their brain's body-map with regard to gender. As with everything relating to gender, preference for one sexual characteristic does not automatically mean preference for all the others, though there is a high correlation.