Skip to main content

Two Sexes

From Aristotle to modern biology, sex has been defined in terms of reproductive function. In humans, reproduction requires the union of two complementary gametes: sperm (male) and egg (female). Every individual is organized, developmentally and anatomically, around one of these two reproductive roles. So, it would seem that the biological category of sex is binary, because the reproductive system itself is binary.

Philosophical essentialism holds that categories are defined by their essential characteristics. The essence of biological sex is gamete production. Despite variations in anatomy, hormones, or chromosomes, no third type of gamete exists in humans. Therefore, the essential classification remains twofold: male and female. Intersex variations do not introduce a third sex but represent atypical expressions of one of the two reproductive categories.

Philosophy of science distinguishes between exceptions and categories. Exceptions do not negate categories when the category captures a universal norm. For example, a person born with a missing limb does not disprove that humans are a two-armed species. Likewise, the existence of intersex conditions does not disprove the binary structure of sex; it confirms that they are deviations from the norm.

To expand sex categories beyond male and female would imply the existence of a third reproductive pathway, which does not exist in humans. To maintain ontological clarity, sex should be recognized as strictly binary, even while acknowledging atypical conditions.

Philosophical confusion often arises from conflating biological sex with gender identity. Gender in my opinion, is a social, cultural, and psychological construct and may admit diversity. Biological sex, however, is a matter of physiology and reproduction. By maintaining the distinction, we can affirm both the binary nature of sex and the diversity of gender without contradiction.

My current conclusion:

There are only two biological sexes within the human species because sex is defined by reproductive function, rooted in gamete production, and universally expressed in male and female forms. Intersex conditions do not constitute a third sex but variations of the two. Philosophically and biologically, the binary classification of sex is sound, coherent, and necessary for conceptual clarity.

Chromosome Counting​

“It’s a scientific fact that humans come in two varieties: XX for female and XY for male.” Except:

  • You can be born appearing female, but have a 5-alpha reductase deficiency and grow a penis at age 12. This is known in the Dominican Republic as guevedoces.

  • You can be born legally male with an X and a Y chromosome, but your body is insensitive to androgens, and you appear female.

  • You can be born legally male with an X and a Y chromosome, and have a penis and testes, and a uterus and fallopian tubes.

  • You can be born legally male with an X and a Y chromosome, but your chromosome is missing the SRY gene, which gives you a female body.

  • You can be born legally female with two X chromosomes, but one of the Xs has an SRY gene, which gives you a male body.

  • You can be born legally female with two X chromosomes — and also a Y chromosome, which gives you a male body.

  • You can be born legally female with two X chromosomes, but your adrenal gland doesn’t produce enough cortisol, and your body develops as a male.

  • You can be born with XX chromosomes — and XY chromosomes (chimerism).

So the next time you attempt to use science as justification for your bigotry, remember that God created humans in many variations, and maybe stop trying to stuff everyone into little “male or female” checkboxes.