Definition:Sex is based on hormones
Sex is based on hormones is an invalid definition of sex commonly used in left-wing arguments and LGBTQ activism in order to undermine the binary nature of sex, often by pointing to the fact that some females have more androgynous hormones while some males have a more female-like hormonal profile, in order to claim that there is a continuum between male and female, an instance of the continuum fallacy. While androgens and estrogen hormones are part of the biological mechanisms that participate to sex determination during development in certain species, it appears that these particular mechanisms only started playing a role in a subset of animals after the evolution of lampreys: "Hormonal control over sexual dimorphism appears to be a relatively recent evolutionary novelty: if the androgen receptor was created by a gene duplication after the lamprey lineage diverged from other vertebrates, then androgen-mediated masculinization and estrogen-mediated feminization must be unique to the gnathostomes."[1].
Because the particular hormonal systems determinating sex can vastly differ across species, the definition of sex as the particular levels of hormones one has is too restrictive to capture the natural phenomenon. Thus, a broader proper definition is preferable.
- ↑ Thornton, Joseph W. (May 8, 2006) Evolution of vertebrate steroid receptors from an ancestral estrogen receptor by ligand exploitation and serial genome expansions. PNAS 98:5671-5676. Accessed on January 21, 2022.