At 14, Sam* came out to her parents as bisexual. At 15, she told them she was gay. And then at 16, she told them that she was trans – that the child they had raised as a boy from baby to teenager would now be living as a girl. “I've known for a long time,” says Sam. “I remember praying I'd wake up a girl when I was like six or seven. My friends at the time were all female – I remember I got told a couple of times, ‘You can't do this because you're not a girl.’ And over time that kind of reinstilled in me the understanding that I wasn't a boy either.” According to The Trans Mental Health Study 2012, 48 per cent of trans people attempt suicide in their lifetime and 53 per cent self harm at some point, and despite a supportive family, Sam was one of them. “I knew that I was never going to be able to live as a man was when I found out what puberty was going to entail for me,” she says.

It’s not easy to get a definite number for the trans population in the UK. In its evidence to the 2016 Women and Equalities Committee transgender report, GIRES (Gender Identity Research and Education Society) claimed that 650,000 people “are likely to be gender incongruent to some degree”. There are more born-male than born-female transitioners. However, of that 650,000 (1 per cent of the population), only 30,000 have so far sought medical intervention related to their gender incongruity, while GIRES estimates that a further 100,000 are likely to pursue surgical or hormonal treatments in the future. If you count only those who have or are expected to physically transition to some degree, the trans population of the UK makes up just 0.2 per cent of the whole.

There remains a gap in public understanding on this point. It’s still widely assumed that to be trans is to wish for or undertake some kind of physical transformation – what used to be called “sex change surgery” and is now referred to as “gender reassignment” or “gender confirmation surgery”. Indeed, the most high-profile trans public figures have all undergone hormonal and surgical medical transition of some kind in order to achieve a feminine appearance: think of Paris Lees and Kellie Maloney in the UK, and Janet Mock and Caitlyn Jenner in the US. But these individuals are actually unrepresentative of what the term “trans” has come to mean. For the vast majority, their gender variance will be expressed without permanent physical alterations – by wearing the clothes and hair or makeup styles usually associated with the opposite sex, or by choosing a name and pronouns that better reflect their sense of their own gender. For example, last year Buzzfeed reported on Alex Drummond, who is male and identifies as female without having had any surgical or hormonal treatment – and with a full beard. “I’m widening the bandwidth of what it means to be a woman,” Drummond said.

This can be perplexing terrain, in which it’s not at all clear that everyone is speaking the same language, although they might be using the same words. In popular usage, “gender” is often simply a synonym for “sex”, and it’s unquestioned that “woman” and “female”, and “man” and “male” are naturally and irrevocably paired. (This could be called the essentialist account, or “gender is in one’s pants”.) Essentialism comes in slightly more sophisticated variants too, and one current proponent is Simon Baron-Cohen, Professor of Developmental Psychopathology at the University of Cambridge, who has written extensively on what he calls “the essential difference”, claiming that the male brain is inherently systematising and the female brain inherently empathising, leading to a natural division of roles on the basis of a physical difference. (Baron-Cohen does allow that “not all men have the male brain, and not all women have the female brain”, but the fact that “systematising” roles occupied by men tend to be well-paid and prestigious, while “empathising” ones performed by women are less valuable or even entirely unpaid, is regarded as an unfortunate coincidence.)

Feminist analysis has vigorously challenged that view. In The Second Sex, Simone de Beauvoir famously wrote that “one is not born, but rather one becomes, a woman”, stressing that gender (one’s social role as a woman or man) is something that must be learned – and that this learning process is enforced on the basis of sex. “They are women in virtue of their anatomy and physiology. Throughout history they have always been subordinated to men,” she explained. The qualities of femininity (for example, gentleness, demureness, motherliness) are not inherent properties of female humans, according to the feminist critique of gender, but ones that female humans are socialised to develop, maintaining them in inferiority to men. This could be called the “gender as sex-class system” account.

There is a third version of the gender concept, which superficially seems like a continuation of the feminist account, but on closer examination is actually a mirror of the essentialist one. In this case, physical sex is not considered to determine social role – however, bodily sex and gender are once again unshakeably bonded, with gender presented as an innate property, now located in the brain rather than the genitals. In the book Whipping Girl, trans writer and activist Julia Serano claims that “certain aspects of femininity (as well as masculinity) are natural and can both precede socialization and supersede biological sex.” According to Serano, everyone, whether they’re trans or not, has a “subconscious sex” which determines certain aspects of their personality and preferences. People whose “subconscious sex” and physical sex are in alignment are described as “cisgender” – that is, their gender is “on the same side as” their body. It is “subconscious sex”, rather than physical sex, that is decisive in this account, so that “to feel like a woman” or “identify as a woman” is to be a woman – even if, as in the case of Alex Drummond, the uninformed onlooker would regard you, and indeed treat you, as a man.

The “gender is in your head” version is the most accessible, and the most acceptable, explanation for why some people are transgender. “I did used to use the ‘woman in a man’s body’ kind of malarky,” says Sam. “People can comprehend that, without any critical thinking.” And as transgender rights are enshrined in law, the belief in “brainsex” follows. The US Justice Department, in a lawsuit against North Carolina’s “bathroom bill”, states that: “Although there is not yet one definitive explanation for what determines gender identity, biological factors, most notably sexual differentiation in the brain, have a role in gender identity development.” (Italics added.) Whether the brainsex theory deserves such acceptance is arguable; so too is whether it should even be necessary for a rights-based legal argument to depend on such claims. But while brainsex is not the only explanation for why people are transgender, it is the only one not to be attended by fiery controversy.

In the 1980s, sexologist Ray Blanchard proposed the “two types” model, which divided male-to-female patients into either the homosexual (generally young males attracted to other males, who find it easier to function in a homophobic world when they are perceived as women) or the autogynephile (who he claimed would usually transition in middle age or later, were usually attracted to women, and were sexually excited by the idea of themselves as women). Many trans activists found this theory upsetting. The backlash against the idea of sexuality and gender being connected was so great that, when Michael Bailey addressed it at length in his 2003 book The Man Who Would Be Queen, he was met with a sustained campaign of harassment that targeted his workplace and his family. Some feminists have also interpreted male-to-female transition as a fetishistic act – a masochistic one bound up in the inferiority of women as a class. “The reality of women’s subordination becomes a plaything for men’s sexual excitement,” writes Sheila Jeffreys in her book Gender Hurts.

Other people have suggested that gender incongruence could in certain cases be associated with autism. According to some research, 8-10 per cent of children seen at gender clinics meet the diagnostic criteria for autism (the incidence in the general population is just over 1 per cent). This could mean transgenderism has a neurological basis that is somehow associated with autism, it could mean that being transgender causes symptoms that are diagnosed as ASD, or it could mean that the social complications caused by autism are sometimes interpreted as gender incongruence. That last explanation is the suggestion of Dr Susan Bradley, who worked with gender-nonconforming children at the SickKids hospital in Toronto, Canada: “A significant proportion of the kids who came to our clinic are within the autism spectrum, and you see some of these kids who, as they emerge later on into adolescence, they just feel like outsiders. So their label is ‘there's something not right about me’, and some of them latch on to ‘well I must be the wrong mind or the wrong brain for my sex’.”

Bradley also believes that for some of her patients, especially female ones, gender transition could be a response to trauma, allowing them to regain control of a threatened or violated body: “In the adolescent girls, we had a couple of kids who came in with no earlier history of particular cross-gender wishes or behaviours, but in the context of a sexual assault, they began to take on the role of a male.” (Like Michael Bailey, Bradley's colleague Ken Zucker, the head of the SickKids gender facility, was attacked for not conforming to the current trans political line, and ultimately forced from his job.)

Something in the body, something in the culture, or something in the brain? A fetish, a flight from pain, or an attempt to deal with a baffling social world? Making it even more difficult to describe and analyse these conflicting accounts of gender is the fact that, according to some, even attempting the discussion is to show hostility to trans people: “Once I accepted my own transsexuality, then it became obvious to me that the question ‘Why do transsexuals exist?’ is not a matter of curiosity, but rather an act of nonacceptance,” writes Serano (notwithstanding the fact that she offers her own explanation for the phenomenon in the “subconscious sex” hypothesis outlined above). Adopting the “wrong” line may be punished with extreme outrage – as happened to Michael Bailey and Ken Zucker, as well as numerous feminists including Germaine Greer, Janice Raymond and Julie Bindel. But despite these disincentives, the question is worth asking: just what is gender, and why do we need to know?

***

Dr Joshua Safer of the Boston University School of Medicine works directly with transgender patients as a clinician, as well as researching the subject and teaching it to medical students. With that expertise, you might imagine that he has a working definition of what gender is, but even he seems awed by the complexity. “Ah, that’s an impossible question… The terminology is too hard,” he tells me. Whatever gender is, Safer believes it is an innate physical property. “Personally, I do actually believe that there is a masculine brain and a feminine brain,” he says. And, following Baron-Cohen’s account, he says that these “masculine” and “feminine” brains will usually be found, respectively, in male and female bodies: “For the overwhelming majority of people there is complete alignment.” Where there isn’t complete alignment between someone’s self-perception and their physical sex, Safer argues that this is due to a congenital condition. “Gender identity is independent of body parts,” he says. “It’s its own biological phenomenon, which presumably develops in utero.”

Safer takes pleasure in setting himself against what he calls the “dogma” that gender is wholly learned. Arguments against this idea usually invoke an American sexologist called John Money. In the mid-twentieth century, under Money's direction, a baby who was born male was raised as a girl after his penis was damaged beyond repair during a botched circumcision. Following the belief that it was easier to construct a vagina than reconstruct a damaged penis (and furthermore that it was impossible for a male with a damaged penis to live successfully in the masculine role), the baby was reassigned as a girl. For 30 years, a narrative of baby John’s successful transition to life as Joan was widely held as evidence that gender is both fully socialised and malleable. Then, in 1997, John told his own story under his real name, David Reimer. He had never “felt female”, he said. The “therapy” he underwent as a child had been traumatising, involving looking at images of nude adults and mutual inspection of his twin brother’s genitals, all under Money’s direction. He was treated with hormones to induce breast growth. At 14, Reimer rejected the female identity foisted on him. He requested a mastectomy to remove his breasts and a phalloplasty to create a penis, and lived as a man from his late teens until 2004, when he killed himself.

Reimer’s case is a tragedy, and a disgrace in the annals of medicine. It was also very influential. Until the truth was made public, many babies with intersex conditions or injured genitals were reassigned after the John/Joan example. For Safer, the revelation of its failure is a rebuke not only to medical practice, but also to the politics of sexual equality in general. The belief that gender is malleable, he says, “fit in with a liberal agenda that men and women are relatively the same, and it fit in with a feminist agenda, frankly, that some of the discrimination against women, especially in the workforce, was an arbitrary social construct.” Instead, Safer preaches essential difference – a world where men are men and women are women, even if some of the men started out female and some of the women were born male. “My transgender patients for the most part are conventional,” he says. “If you live next door to them in the suburbs, stereotypical family of four, you would not know that the father in that family was a transgender man.”

In 2015, Safer co-authored a literature review of possible evidence for a biological basis to gender identity. In it, he and his coauthors assessed a range of published papers: some were comparative studies into brain structure, some were cohort studies of intersex children, some were gene studies. Overall, the paper concludes that: “Although the mechanisms remain to be determined, there is strong support in the literature for a biologic basis of gender identity.” This verdict looks likely to be an influential one: for example, GIRES has quoted it in a response to a proposed NHS service specification for the treatment of children and adolescents with gender identity disorder. But is the literature review actually convincing? The search for the biological origins of gender difference is a fraught field. In the gendered world we inhabit, there can be no "control group". And science, far from being neutral, is done by scientists, whose preconceptions are unavoidably shaped by social forces such as sexism.

For example, in the twentieth century, the discovery of the X and Y chromosomes seemed to promise a concrete biological foundation for gendered behaviour. But as Sarah S. Richardson explains in her book Sex Itself: The Search for Male and Female in the Human Female, their respective roles in determining human sex were misunderstood for many years because the chromosomes didn’t conform to gender stereotypes. In the 1920s, the geneticist Thomas Hunt Morgan rejected the idea that the absence of an X chromosome could be the cause of male embryonic sex, not because he had evidence to the contrary, but because it offended his belief in feminine passivity and masculine activity. “There is no warrant for considering the male in this sense a lacking female," he wrote. "The physiology and biology of the males offer much to contradict such a view of his composition." In fact, it was a female cytologist – Nettie M. Stevens – who demonstrated that females are XX and males are XY, so opening up discussion about the function of the Y in sex determination. Somewhat typically, her decisive contributions to the science were overlooked until recently.

In a true experiment, a researcher isolates all possible variables and manipulates the one they want to study while keeping the others constant. A control subject is used to ensure that the outcome is the result of the variable being investigated, and the same experiment conducted many times to ensure that the result is replicated. If we could conduct such studies with humans, then we would be able to say for sure which differences can be attributed to nature, which to nurture, and which are not differences at all. But, ethically and practically, such experiments are off-limits when it comes to human subjects: even if it weren’t morally abhorrent to do so, it’s not possible to isolate all the variables in a child’s upbringing in order to determine which inputs lead to gendered behaviour. Look at the John/Joan case. At the time, it was treated as empirically convincing in support of gender plasticity. Now it’s seen as proof of inherent gender. The larger question is this: was Money really able to test what he claimed to be testing?

Clinical trials are usually carried out "double blind" - for example, in a drug trial, neither doctor nor patient should know if they are receiving the real thing or a placebo. But as Rebecca Jordan-Young says in her book Brain Storm: The Flaws In the Science Of Sex Difference, for a male child to be truly “raised a girl”, his parents would have to truly believe he was a girl. Given that David Reimer’s parents knew he was born with a penis, that would have demanded an extraordinary and unrelenting suspension of disbelief for a family in the mid-1960s. Susan Bradley recalls cases from her own work with intersex children where parents followed medical advice to raise their child in one gender dutifully, but without conviction: “They didn’t know how to say to the doctors, ‘this doesn't make sense’ or ‘we don't like this idea’. And so they did whatever they did, but there was no evidence that the child was… actually raised in a comfortable way in that role.” Not just that, but the versions of “being a girl” and “being a boy” that John Money was using were thoroughly conservative. To become Money’s version of a girl, Reimer was cultivated for the role of wife, mother and homemaker. But two years before Reimer was even born, with the publication of The Feminine Mystique, Betty Friedan had showed that natal women were agitating against that limited status.

John/Joan is an exception in the study of human sex differences. More usually, these are investigated using what are called “quasi experiments”: in these, a scientist hypothesises that a certain outcome is related to a certain input, then seeks a group of subjects who have experienced the input and compares them to a group who haven’t. Because of the potential for confounding factors or unanticipated variables in human subjects, replication of results is essential before they can be accepted as true. “Unlike true experiments, where the controlled circumstances of the research can give strong evidence about cause-and-effect relationships from even a single study,” writes Jordan-Young, “quasi experiments only become convincing when multiple studies, related in specific ways, all point to the same conclusions.” The review co-authored by Safer certainly includes multiple studies, and they all appear to point to the same conclusion – biological basis for gender identity. But crucially, they find many different possible biological explanations, so it's hard to use them to support each other. One study finds a possible genetic cause for transgenderism, for example, and another finds a possible cause in the uterine hormonal environment.

Sometimes the research presented by Safer and his colleagues is actively contradictory. At one point, it cites a study that found trans women had a larger volume of grey matter in the putamen of the brain relative to a control group of non-transgender males, and another study finding that trans women had a significant volume reduction in the putamen compared to male and female controls. When I ask Safer about this, he agrees that “opposite data were found, which leads me to suggest that perhaps the original study was a coincidence and we would not use that as any sort of indicator there”. The published paper, however, excises this caution and suggests that the contradictory findings actually corroborate each other: “Although these findings differ… they still indicate that certain brain areas in the transgender group have characteristic structural features compared with controls.” If the John/Joan experiment was once given immunity from criticism because it reinforced a certain political outlook, it seems that the same privileges are now extended to anything supporting the “born this way” theory of gender identity development.

Many scientists have concerns about the brainsex theory. “My experience of science,” says Professor Sophie Scott, drily, “is that your threshold for accepting data can be really low if you say you’re looking at sex differences”. Scott works at University College London, where she researches the neurobiology of speech perception, and she’s scathing about the standard of evidence for congenital structural differences between male and female brains. “I think we have a cultural belief in – for want of a better phrase – fairy stories,” she says. “You’ll hear people say, it stands to reason that our bodies are different between men and women, therefore our brains must be different. Nobody’s saying that about the kidneys or the stomach or the skin, but somehow it’s such an easy and pleasing account. And scientists are not free from that.” Given the dedication with which researchers have hunted for brain difference, perhaps the most telling thing is how little they’ve found: “I’ve been doing functional imaging studies [of the brain] for nearly 20 years now and I never look at sex differences, because they’re not very interesting. All the other evidence seems to suggest from a brain perspective that, for language, there are no big differences between men and women.”

For Scott, gender isn’t something inside you, but something imposed on you. “Gender is the outcome of the way that we treat human beings from the minute they're born and people are interested in knowing if they're boys or girls,” she says. “We then start constructing a world round them.”

***

Occasionally, it’s not immediately obvious whether a baby is male or female. According to the Intersex Society of North America, about one in every hundred babies born has genitals that differ in some regard from typically male or typically female. As with David Reimer, the treatment of these children has often been regarded as the test of whether gender is inborn or acquired, and Safer gives particular prominence in his literature review to studies of intersex children, especially those with congenital adrenal hyperplasia (CAH). CAH causes individuals with the female XX genotype to appear more male: typical symptoms include fused labia, an enlarged clitoris, and fusion of the vagina and urethra. A girl with CAH will have a uterus, but her periods could be irregular or absent; she might also develop facial hair and an unusually deep voice for a girl.

A 2004 study highlighted in the Endocrine Practice literature review found that females with CAH who were raised as girls were more likely than the general female population to transition to living as a man later in life (although the majority still went on to live as women). In Safer’s view, the fact that these genitally ambiguous children sometimes went on to reject the gender they were consciously instructed in (and often surgically modelled to conform to) is compelling support for the idea that gender identity is fixed prior to birth. The theory is something like this: in the same way that the genitals of a female with CAH develop to have a more male-typical structure, so does the brain.

There are a couple of problems with this account. Firstly, there is no such thing as a “male brain” or a “female brain”, certainly not in any way that’s analogous to male and female genitals. If, say, you were taking part in a particularly macabre experiment and were presented with a disembodied penis or vulva, you could tell immediately whether the individual the body part had come from was male or female; but there’s no way to tell whether a brain came from a man or a woman simply by looking. That means it doesn’t make sense to talk about the brain being “virilised” in the same way as the genitals, and it also means that those with intersex conditions can’t be readily compared to those with normal sexed genitals who seek reassignment.

The other problem relates to the tricky cultural side of gender. As we’ve already seen with the Reimer case, the treatment of children with atypical genitals could be very unlike the upbringing of the average male or female child. Firstly, there was the likelihood of genital surgery: until the intersex rights movement challenged the practice, the medical default was to operate. Safer suggests that this was based on the assumption that men and women were fundamentally alike, but it also derived from and reinforced the idea that men and women should be different. The remodelling of ambiguous bodies was done, not to prove that male and female were the same but, in the words of Anne Fausto-Sterling in her book Sexing the Body, because “to maintain gender divisions, we must control those bodies that are so unruly as to blur the borders”.

This anxiety was not limited to physical appearance. The role that an intersex child might go on to take in society played a huge – perhaps dominating – role in the consideration of treatment. For example, Dr Maria New was a physician who promoted the off-label use of the drug dexamethasone for pregnant women who were at risk of having a child with CAH (a therapy that was strongly criticised on ethical grounds in a 2012 paper by Alice Dreger, Ellen K. Feder, and Anne Tamar-Mattis). New explained her treatment aims like this: “The challenge here is… to see what could be done to restore this baby to the normal healthy appearance which would be compatible with her parents presenting her as a girl, with her eventually becoming somebody’s wife, and having normal sexual development, and becoming a mother.” Notice how the emphasis is not on the girl herself, but how she will be able to fulfil her expected sex role in relation to other people: uncomplicatedly a daughter, then “someone’s wife” (implicitly, the girl is not “someone” here, and only exists in relation to the man she will hopefully marry), and ultimately a mother. The idea of a woman growing up to reject these roles was unacceptable in New’s framework: in fact, she was particularly anxious to prevent “behavorial masculinization” in girls with CAH, which she defined as “lesbianism and tomboyism”. (There is some irony in a female doctor worrying about girls transgressing into male-typical behaviours, given that women have been historically excluded from medicine.)

Concern to maintain the clear divide of physical sex was accompanied by a concern that girls grow up to acquire feminine, submissive, and above all heterosexual behaviours. And while medics treating girls with CAH attempted to ready their patients for future sexual relationships, the surgery performed on them to “normalise” their genitalia was performed with a highly gendered perception of what is “normal”. Female pleasure in sex, for example, was not a priority: shortening the clitoris of a girl with CAH meant she no longer looked as though she had a penis, but unsurprisingly, the majority of girls who received this treatment suffered impaired clitoral sensation. If surgeons operated on the patient to create a vaginal opening, penetrative sex was often impossible, or if possible, painful.

Added to that, the ongoing “care” to which girls with CAH were subjected was unambiguously traumatising: “In one follow-up study,” writes Rebecca Jordan-Young, “women with CAH ‘used a language of “rape”, “invasion” and “violation” when talking about vaginal examinations and other procedures carried out during visits to paediatric and adult clinics.’” Dreger, in her book Galileo’s Middle Finger, describes how the pediatric urologist Dr Dix Poppas tested the sexual function of CAH girls aged six and up by applying a “medical vibratory device” to the girl’s thigh, labia, and clitoris.

To have an intersex condition is by definition to have an atypical upbringing. In the most egregious cases, intersex children have been, by their own account, sexually violated in the name of making them “healthy”. It is impossible to use them as an uncomplicated test case of gender development when we know they were treated in ways that not-intersex children would never experience. But the treatment of girls with CAH, like the treatment of David Reimer, does tell us a lot about the social enforcement of gender: how function-impairing body modifications were considered acceptable in the service of maintaining proper gender divisions, and how the ideal female role was conceived as one of marriage, maternity, and penetrability.

***

Thanks to the efforts of campaigners for intersex rights, it’s no longer the default for children with ambiguous genitals to undergo surgery. Nevertheless, anxiety about “gender appropriate” play persists, and while women have generally become more accepted in the workplace and gained many legal rights in the time since the John/Joan experiment, in some ways the gendering of childhood has become more extreme. “I'm 48,” says Sophie Scott. “I've seen toys change what would be considered to be the appropriate gender. When I was a little girl, Lego was something boys and girls played with; and it's gone largely into something that boys do, and has been very much marketed along those lines.” Toys and activities are endemically sold as either “for girls” or “for boys”, with a persistent colour code of pink and blue. Girls are steered towards passive, feminine activities, while boys are pushed towards active, masculine endeavours: Igloo books, for example offer a choice between either 2001 Pretty Stickers For Girls (pink, inevitably) or 2001 Awesome Stickers For Boys (in blue). Girls are pretty, boys are awesome, and the message is repeated to children in hundreds of ways every single day.

And as definitions of appropriate gender behaviour for children have narrowed, deviation has become increasingly pathologised. Writing in the Chicago Tribune, Tucker Fitzgerald (father of a six-year-old male child living as a girl) says:“I tried to raise my daughter as a boy. Complete with blue walls and Tyrannosaurus rex pajamas. I gave her my father's name. Took her to church on Sundays. Her siblings have had no trouble with the genders assigned them. But it just didn't work for her.” Once the child’s preferences for “unicorns and mermaids and soccer” were clear, it seemed clear also that this child must be a girl rather than a boy. (It’s worth noting that for a male child living in the UK, liking “soccer” would be considered appropriately masculine.) In the BBC documentary I Am Leo, the mother of Leo (a trans boy) explains how she realised her daughter could not be a girl because Leo (then Lily) prefered “boys’ toys” and wanted short hair – even though, the mother says to Leo, “I used to try and convince you you looked so nice.” The programme underlines this gender message by using an animation to explain the effects of hormones on the adolescent body in which the male figure is blue and human-shaped, and the female figure pink and skirted.

Rather than being seen as simply preferences, a liking for mermaids over dinosaurs or short hair over long is treated as the ambassador of the child’s underlying, authentic gender – what Julia Serano refers to as “subconscious sex”. The expectation becomes that the child will in time embark on a course of treatment (puberty blockers, hormone replacement therapy, sex reassignment surgery) to bring their body in line with their gender. But this belief that gender is innate and irradicable is not shared by all practitioners who work with gender-nonconforming young children. Dr Susan Bradley defines gender as “the self-perception of a person as either male or female or in-between”, but she isn’t drawn to biological explanations: “It is a complicated psychological phenomenon, that's how I would view it,” she says, “as opposed to a brain-based thing.”

Rather than attempting to bring patients’ bodies into line with an arguably non-existent gender identity, Bradley says that her work at SickKids aimed to help young gender-nonconforming children “feel secure and safe and not in need of what I'm gonna call a defensive solution”. “Defensive solution” is Bradley’s term for identifying as the opposite sex, and the fact that the Toronto clinic supported desistance in its patients formed one of the key planks in the attack on its director Kenneth Zucker, leading to his exit from the unit. Despite studies suggesting that 80 per cent of gender non-conforming children go on to live in their original gender as adults, it was claimed that the clinic performed “conversion therapy” – that is, that they “converted” trans children to non-trans children (the term “conversion therapy” usually refers to a discredited form of counselling that claims to be able to quell homosexual feelings or activity). But Bradley is adamant that their work was in their patients’ best interests, particularly the younger ones: “In the young kids, if we could help them not need that, we felt very comfortable supporting them in becoming whoever they were gonna become, but without the surgery if that were possible.”

While avoiding surgery and lifelong hormonal treatment was seen as a good outcome, Bradley says the aim of the clinic was not to “convert” children: “A number of these kids ended up being gay and lesbian, and from our perspective that was fine. What we were trying to avoid was this need to continue to believe that the only way they could feel OK was to be the other sex.” (According to the NHS Tavistock and Portland Gender Identity Development Service, the biggest British centre treating children with gender issues, 67.6 per cent of natal female patients referred to the clinic are attracted to females, and 42.3 per cent of natal males are attracted to males, so there is clearly a substantial intersection between homosexuality and gender identity disorders.)

For older patients at SickKids, Bradley says the approach was different: “When we saw kids at age 13, 14, 15 – if they had been convinced for some time that transitioning was critical to their being able to function and feel OK about themselves, we supported that, so we would send them to endocrinologists and work with them in support of ways to do what they had to do.” That describes the situation of Sam*, now aged 20, for whom transition is the only conceivable pathway, and for whom speculation about the causes of transgenderism are tediously abstract. “I have what I have now for whatever reason, and it needs to be sorted out irregardless,” she says. “I've never been afforded another option than physical transition.” The problem is that, as the doctrine of gender identity draws tighter, options become ever narrower – and while transition is appropriate for Sam, that doesn’t mean it’s necessarily the right approach for all patients presenting with gender identity disorders.

In fact, it seems unlikely that “gender identity disorder” - the current diagnostic term - describes one coherent phenomenon at all. In the absence of compelling evidence for brainsex, what we appear to be looking at is a variety of conditions: some might be trauma-related, some might be associated with autism, some might be a response to homophobia, and others might be paraphiliac in nature. But at the moment, all are being treated as though they originated from a mismatch between brain and body which prevents a person from being recognised in their correct social role. The implication of that being that anyone who isn’t transgender has the converse experience - of a match between brain and body and a natural affinity with their social role of man or women. In a society where women’s work is less valued, where women are prevented from holding positions of power, where women are subject to particular kinds of harassment and violence because they are women, and where children are indoctrinated from infancy in the idea that girls are “pretty” and boys are “awesome”, the idea women "identify" with all this should give us pause.

***

“Is it wrong to call it empathy when you trust the fact of suffering but not the source? How do I inhabit someone’s pain without inhabiting their particular understanding of that pain?” asks Leslie Jamieson in her essay “Devil’s Bait”. Transgender people can point to compelling evidence of violence, unhappiness, and discrimination, and argue for medical and legal interventions to remedy them. But the fact of suffering is not evidence that the sufferer has unimpeachable insight into the source of that suffering. The widely embraced “inherent gender” explanation holds that there is such a property as gender identity, which every individual has, entirely separately from socialised gender roles, which only some people will be conscious of, and of which the individual is the ultimate arbiter. This is in every regard an extraordinary claim. As analytic philosopher Rebecca Reilly-Cooper has explained, it is also an incoherent claim, because there is no standard by which anyone’s assertions about their own gender can be disproven: “If we’re unwilling to allow that an individual can ever be mistaken about their gender identity, if we’re unwilling to allow that there might be any objective criteria at all about what it means to be a man or a woman, then claims to identify as a man or a woman become unintelligible.” If no one can say what it means to be a man other than to feel like one, what does it mean to feel like a man?

And yet this claim has become the justification and basis for trans activism, and is increasingly influential in the development of legislation. In the UK, the Equalities Act uses "gender reassignment" as the protected characteristic which must not be discriminated against. In other words, in Britain, someone who has obtained a gender recognition certificate, and changed their passport and birth certificate, must be treated as their desired gender for legal purposes. (The process for doing this is bureaucratic, and requires the individual to live in their acquired gender for two years. However, neither hormones nor surgery are mandatory.)

But the Trans Inquiry conducted by Maria Miller's Women and Equalities select committee earlier this year recommended that the protected characteristic should now become "gender identity", and changing this should be possible by a simple form on a website. The US is also moving in this direction, with US attorney general Loretta Lynch ruling that schools must "treat a student’s gender identity as the student’s sex". The Department of Justice guidance adds: "A school may not require transgender students to have a medical diagnosis, undergo any medical treatment, or produce a birth certificate or other identification document before treating them consistent with their gender identity."

It must be noted that where the aim is for every person to be treated in accordance with their gender identity (rather than their birth sex, or their perceived gender following transition), this leads to pressure on women rather than on men. It is services intended for women, not services intended for men, which have been most vehemently attacked for failing to be trans inclusive: rape crisis centres (Vancouver Rape Relief), abortion rights campaigns (A Night of a Thousand Vaginas), and women-only music festivals (Michfest). Gentleman's clubs - those all-male bastions of the Establishment - have not been targeted for protests. Campaigns for trans women prisoners to be transferred to female prisons are common, and often make no distinction between individuals who have substantially transitioned and individuals such as Joanne Latham, a male prisoner who had taken no steps towards transition beyond a name change (Latham, who was guilty of three attempted murders, died by suicide in December 2015). Campaigns for trans men to be transferred to male prisons are rare to the point of non-existence.

There are several explanations for this imbalance in the case of prisons. One is the relative number of incarcerated trans women compared to female prisoners: according to a Swedish cohort study, trans women “retained a male pattern regarding criminality”, meaning a trans woman is more likely to end up in prison than a natal woman. Another is that conditions in women’s prisons may be regarded as preferable: even though the same study found that trans men adjusted to a male pattern of criminality after transition, a trans man allocated to a women’s prison has a very good reason not to lobby for transfer to a larger and more violent men’s prison. A third is that a few trans women may have less than innocent motivations for wanting to be housed with female inmates. In 2013, Paris Green – a trans prisoner who was awaiting genital surgery, and consequently had a functional penis and testicles – was removed from Cornton Vale women’s prison after having sex with female prisoners.

But there’s a further way to understand why pressure to be inclusive falls so consistently on women, and it’s fundamental to how “woman” functions as a category. Simone de Beauvoir noted that “woman” as a class is the negation of “man”: “she is simply what man decrees… She is defined and differentiated with reference to man and not he with reference to her; she is the incidental, the inessential as opposed to the essential. He is the Subject, he is the Absolute – she is the Other.” That is to say, woman is “non-man”, which is precisely the term Green Party Women used (to great derision) in April this year. In a statement on Facebook, the group said: “Green Party Women, as a whole, are happy with terms such as ‘non-men’ to be used to describe women, including transgender women, and non-binary people as a collective term. This is to avoid further marginalising certain groups of women, particularly those who have been excluded from women’s movements for far too long.” In this, Green Party Women echoed Julia Serano in the book Excluded, who insists on a definition of feminism that contains no reference to patriarchy, male violence, or even to the power imbalance of sexism: “we [i.e. feminists] should envision ourselves as working to bring an end to all double standards based on sex, gender, and sexuality, as well as any other double standard that is unjustly used to demonize, delegitimize, and dehumanize other human beings.”

It is impossible to talk about gender without talking within it. All of us have a position within its class hierarchy, and that position is dictated not by a subjective feeling, but by the way other people respond to us over a lifetime, educating us in the part we are supposed to play. And yet the theory of innate gender requires us to believe that gender is both natural and good, while its application to women’s politics and women’s spaces replicates ancient misogynistic habits of denying women their own limits. As this goes on, the needs of gender-nonconforming individuals who might not be best served by gender identity theory are disregarded to an alarming degree. GIRES, in its representation to the NHS, has even suggested that gender identity treatment could resolve cases of autism: “Anecdotally, young people who have been successfully treated, are often described as having no residual ASD. The symptoms have disappeared once the dysphoria has been treated.” (Asked for a response to this, the National Autistic Society gave me the following statement: “We think that every person on the autism spectrum should be able to live the life they choose, which includes being able to transition genders with the help of a team who understand them and their autism. However, no intervention will ever eliminate a person’s autism.”)

There is a real danger that an unproven theory of innate gender identity is now directing treatments for individuals whose “gender variant” behaviour or identity could have any of multiple causes – causes which will not necessarily be resolved by transition. (The Swedish study found that “Persons with transsexualism, after sex reassignment, have considerably higher risks for mortality, suicidal behaviour, and psychiatric morbidity than the general population”, and suggested that while transition relieved dysphoria, it was not a universal panacea.) Meanwhile, we are building a political and legal edifice on foundations which are, to say the least, scientifically shaky. There is no doubt our society can be unkind and even violent to those who do not conform to gender norms. But is accepting a theory of innate gender identity, with all its associated costs for those born female, really the best way to stamp out that prejudice?

* name has been changed