Biological sex is not binary

Jump to navigation Jump to search

Biological sex is not binary is a family of arguments made in discussions and debates of the nature of sex as well as LGBT rights and revendications. The fallacious argument generally relies on definitional blurring and attacking a strawman. These arguments fail to address the steelman of the binary definition of sex, which is the ability to contribute a sperm cell or an egg cell to an act of reproduction.

Examples of definitional blurring (in which the definition of sex is blurred around indirect proxies of sex rather than the steelman)

  • In a 2018 NYT piece[1], Anne Fausto-Sterling argues that there are, at birth, "five layers of sex," which are: chromosomal sex, fetal gonadal sex, hormonal sex, internal reproductive sex and external genital sex. Of course, these are all just biological mechanisms which function to develop sexual capability, that is, the ultimate ability to produce a sperm or an egg as part of the act of sexual reproduction. Therefore the fact that these mechanisms can go wrong or act in non-binary ways is unrelated to the final reproductive outcome as part of the binary of sex.
  • In a 2019 Massive Science piece[2], Liza Brusman brings the focus unto sex proxies, rather than the act of reproduction, including sex organs and sex hormones.

Examples of strawmanning

  • In a 2020 blog post in Scientista[3], Darren Incorvaia claims that sex is not binary because some people are true hermaphrodites (i.e. they can produce both ovaries and testes). This, of course, misses the point of whether sex is binary in the steelman version of the argument. Even if someone was able to produce both sperm and egg, this would simply mean that they are the male of a given reproductive act and the female of another. Sex remains a binary as they could not have participated to either reproductive acts as anything else than a male or a female.
Statement of the claim Biological sex is not binary
Level of certainty False
Nature Factual
Counterclaim Biological sex is binary
Dependent on


Dependency of


  1. Fausto-Sterling, Anne (October 25, 2018) Why Sex Is Not Binary. New York Times. Accessed on January 16, 2022.
  2. Brusman, Lisa (June 14, 2019) Sex isn't binary, and we should stop acting like it is. Massive Science. Accessed on January 16, 2022.
  3. Incorvaia, Darren (July 16, 2020) Why Sex Isn't Binary. Scientista. Accessed on January 16, 2022.