From the ever wise Drs Emma Hilton and Colin Wright:
In humans, as in most animals or plants, an organism’s biological sex corresponds to one of two distinct types of reproductive anatomy that develop for the production of small or large sex cells—sperm and eggs, respectively—and associated biological functions in sexual reproduction. In humans, reproductive anatomy is unambiguously male or female at birth more than 99.98% of the time. The evolutionary function of these two anatomies is to aid in reproduction via the fusion of sperm and ova. No third type of sex cell exists in humans, and therefore there is no sex “spectrum” or additional sexes beyond male and female.
Sex is binary.
There is a difference, however, between the statements that there are only two sexes (true) and that everyone can be neatly categorised as either male or female (false). The existence of only two sexes does not mean sex is never ambiguous. But intersex individuals are extremely rare, and they are neither a third sex nor proof that sex is a “spectrum” or a “social construct.” Not everyone needs to be discretely assignable to one or the other sex in order for biological sex to be functionally binary. To assume otherwise—to confuse secondary sexual traits with biological sex itself—is a category error.
https://fairplayforwomen.com/scientistsspeak/