I think the most obvious difference— and one that, thankfully, is beginning to be subjected to greater scrutiny— is that it reifies the traditional mind/body divide. The one-sex model, for all its flaws and errors, ultimately grasps the notion of the individual as a product of integrated systems and processes, allowing either one’s sexed traits to influence one’s selfhood, or one’s selfhood to influence one’s sexed traits. Of course, the lack of separation between body and mind— i.e. the need to view body and mind as an integrated whole— is not only (unsurprisingly) more accurate than the binary distinctions favoured in the nineteenth century, but generally supports a more sensible understanding of gender diversity (amongst everyone, not just trans folks). In other words, the idea of a ‘settled’ science that confirms a sharp distinction between sex and gender simply does not exist.
What’s important to note in terms of rhetoric, discourse and theory— and which Laqueur stops short of, because of his periodisation— is that the concept of a separation between sex and gender- in the contemporary sense- derives from medical professionals working after Freud: John Money, Madison Bentley and Robert Stoller (an older but quite accessible text on this is How Sex Changed, by Joanne Meyerowitz, but also Jules-Gill Paterson does current work and writing around this period). Their theories were then taken up and co-opted outside of their original (if debatable) scientific context, filtering into both feminism(s) and academic fields (gender studies, women’s studies, queer studies etc). So arguably, most people discoursing about gender now are merely working with not only received knowledge, but something that’s emerged like the end of a game of telephone: sex is biological fact, gender is identity (i.e. mental and/or emotional) isn’t exactly what was said in the beginning, but it’s what we wound up repeating at the end.
So while the sex/gender split echoes the binary divisions common in English, I think it’s less a product of linguistics and more the use and abuse of theory. As Paterson notes in her post:
“Actually, the word “gender” didn’t mean at all what it does today until the 1950s. Before then, the word “sex” had to do all the heavy lifting. But in that decade a cohort of psychologists, endocrinologists, and plastic surgeons who had been forcing horrifying experiments on intersex infants and children for decades needed a new theory of human development and identity to save the binary.
The new word gender, by which these researchers meant our deeply felt sense of being a boy and/or a girl, was supposed to fix that conceptual weakness, to give the binary new teeth. And it did, with a kind of sleight of hand that we are still trying to outsmart all these years later. John Money, a psychologist at the Johns Hopkins Hospital in Baltimore, knew that finding a biological basis for sex could never be the justification for enforcing a match between anatomy and identity. Instead, he changed the terms of engagement. From now on, the issue was not if humans were biologically binary, but rather “the life adjustments of patients in our series”—how normal they felt, or how well they adapted socially. With that twist, a gender identity that did not conform to a binary body could be subject to medical control because it might lead to social stigma, not because there is anything unnatural or unhealthy about it.
Of course, however, ‘gender’ as a concept was then picked up and utilised by ‘cis people’ even more broadly (Paterson problematises the term in her article) for analyses that were not only un/non-scientific, but which bolstered the absolutist notion of a sex/gender dichotomy throughout numerous fields and ideological approaches across the political and philosophical spectrum. In other words: like the one-sex and two-sex models, the sex/gender dichotomy is simply the most recent (pseudo-scientific/theoretical) construction that we’ve come up with and, in reality, is less than a century old.
(Note: Meyerowitz and Paterson work in the context of US trans history, so while the discourses they reference are essential to how sex/gender are understood in the Anglosphere, their broader observations about historical patterns and experiences of trans people are not always relevant outside the US context, or are currently under/not researched).
