Definition:Sex is based on chromosomes

Sex is based on chromosomes is an invalid definition of sex commonly used in left-wing arguments and LGBTQ activism in order to undermine the binary nature of sex. While the statement is true of certain species, it fails as a definition of the phenomenon of sex as it is not broad enough to capture all phenomena that belong to the category of sex, such as sex in species that do not use chromosomes to determine sex. Examples include:

• Bonellia viridis, a marine worm that become female when isolated and male when in presence of a female.

• Environmentally-induced sex selection such as temperature impacting sex determination in sea turtles{Cite web|url=https://www.sciencedirect.com/science/article/pii/S0016648002005117?via%3Dihub%7Ctitle=Expression profiles of Dax1, Dmrt1, and Sox9 during temperature sex determination in gonads of the sea turtle Lepidochelys olivacea|last=Maldonado et al.|first=|date=October 15, 2002|publisher=General and Comparative Endocrinology 129:20-26|access-date=January 21, 2022}}.

Due to the existence of sex-determination mechanisms that are not dependent on chromosomes, the definition of sex as the chromosomes themselves is too restrictive to capture the natural phenomena. Thus, a broader proper definition is preferable.