These various developmental anomalies of don't map to some sort of sex continuum though - they are all discrete conditions caused by specific disorders, and from a biomedical point of view are still analysed within the framework of male and female sex development.
There's certainly ongoing debate amongst medical professionals on how best to categorise intersex conditions. I don't think models like the 'gender unicorn' really help with this though, it's not sufficiently technical, and seems more geared towards people who don't wish to conform to cultural stereotypes of gender, but would like some way of describing it.
> The author seems to be talking about sex in terms of gametes - i.e. sperm and eggs. They make the claim that there is an absolute sex difference between male and female sexes in terms of this gamete structure. I am happy to take them on their word on this point.
> But this is obviously not the only definition we have for sex.
It's the only definition that matters when it comes to the field of biology.
The people who insist that sex is a continuum of some sort are getting confused with sex and sex-linked traits. As an example of the latter, consider testosterone levels. If you sample a random population of humans and plot this, it shows a bimodal distribution.
Some will argue that this demonstrates sex is a continuum, but what it really shows is two discrete populations that have an average difference between them: males and females.
As an example: a man with lower testosterone than most other men is not less male, or more female. He's just a male with below-average testosterone levels. The value of this hormonal trait doesn't define or alter his sex.
There's certainly ongoing debate amongst medical professionals on how best to categorise intersex conditions. I don't think models like the 'gender unicorn' really help with this though, it's not sufficiently technical, and seems more geared towards people who don't wish to conform to cultural stereotypes of gender, but would like some way of describing it.