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Biological sex: the gamete definition

Sex is binary, observable from birth, and immutable. Two categories — determined by the type of gamete the organism produces or would produce. No spectrum, no third option, no "assignment".

The definition: gametes, not sensation

In all anisogamous organisms — including humans — there are exactly two gametes: the small, mobile ones (spermatozoa) and the large, immobile ones (oocytes). The definition reads: female = the developmental trajectory aimed at the production of large gametes; male = the trajectory aimed at small gametes. No third gamete exists. No intermediate form exists. The definition applies to the entire class of mammals and to virtually all multicellular animals. This is not the opinion of Colin Wright or Emma Hilton — it has been the standard of evolutionary biology since Parker, Baker & Smith (1972) (source).

Gender is observed, not "assigned"

The phrase "sex assigned at birth" is not a neutral description but an ideological intervention. A midwife does not assign sex—she observes what has already been there since conception. The trick of "assigned" turns sex into a social act that can be undone, thereby paving the way for the claim that "trans women are women." Note the circular reasoning that arises from this and the metaphysical claim underlying it.

DSDs are not a third category.

Disorders of Sex Development (DSD) such as AIS, CAH, or 5α-reductase deficiency are pathological abnormalities within one of the two developmental trajectories — not evidence for a third sex. Intersex in the strict sense (chromosomal sex does not match the phenotype, or the phenotype cannot be classified as male or female) occurs in about 0.018% according to Sax (2002); the 1.7% estimate of Fausto-Sterling also counts conditions such as Klinefelter syndrome, Turner syndrome and late-onset adrenal hyperplasia, which most clinicians do not regard as intersex (source). Compare: blindness does not refute the fact that vision is a visual system trait. See chromosomes and gametes for the molecular substantiation.

Intersex in the debate

A girl with CAIS is a girl with a developmental disorder — not a third gender and not a mascot for non-binary ideology. See intersex for the substantive delineation.

What is at stake

When sex is no longer materially observable but a matter of feeling, the category of woman disappears as a meaningful legal, medical, and sporting entity. Statistics on violence against women, cervical cancer screening, and performance fairness in sport become illegible. See the feminist critique and the analysis of sex versus gender, in which precisely this blurring is analyzed step by step.

The biological definition of sex

In evolutionary biology, males are defined as the sex that makes the smaller gametes; anisogamy and the two sexes are evolutionarily very stable (Lehtonen & Parker 2014; source). Variation in DSD conditions does not make sex a spectrum.