Comment by fringol__

That textbook chapter you linked is quite revealing, thanks. I see that diagram in particular as a good demonstration of how the "sex is a spectrum" concept can't possibly work in practice. The number of arrows criss-crossing back and forth shows how impossible it would be to order disorders of sex development (DSDs) into a spectrum in any logically consistent manner.

More importantly, there's not really any reason to do so, as every one of those DSDs can be explained with the binary sex model and a mechanistic understanding of human sex development. Take 5-alpha reductase deficiency for example, it's caused by mutations in the SRD5A2 gene, which adversely affects conversion of testosterone to dihydrotestosterone, causing internal testes and an underdeveloped penis, but otherwise normal male sex development including testosterone-driven male puberty. It would be pointless to try to place this somewhere on a spectrum, as it offers no additional explanatory power and just obfuscates the detail.

In your spectrum model, you seem to be using the word "sex" to describe some sort of undefined (and apparently undefinable) composite statistical scoring of a set of dissociated sex-linked characteristics, that is focused almost entirely on those present in humans. However, this is not how biologists would typically think of sex. Fundamentally it is about evolutionary questions, like: why does sex exist, why is it a stable reproductive strategy across almost all complex life? And it is about developmental questions: what makes sexed bodies, what are the underlying mechanisms? I don't understand how adopting a "sex is a spectrum" belief would help answer these.

You mention hermaphrodites but again I don't see how the spectrum model does anything but fail here? It offers no useful insights - the binary sex model is perfectly adequate to explain that an individual embodies both female and male halves of the reproductive system.

I hope this helps clarify my points, interested to read your response.