In many societies, gender has historically been understood as a neat, orderly, and intuitive model. The concept of “man” referred to people who had the same kind of male body, presented in a way that was regarded as male, and took male-designated roles. The concept of “woman” was defined in the same way. These two categories were considered to be permanent, inescapable, and complete: everyone was placed into one of them, and migration between them was unthinkable.

Under this model, explicit definitions of gender involving anatomy, genetics, and sex assigned at birth were associated with whatever clusters of traits were typically exhibited by men and women. And just as it was assumed that someone who was assigned male or female would present themselves in a certain way according to their gender, it was also assumed that everyone who presented as a man or woman had the same anatomical and genetic makeup.

The recognition of transgender people as a discrete phenomenon has changed all this. We’ve come to realize that it simply isn’t accurate to view assigned sex, physical anatomy, sex chromosomes, gender identity, gender roles, and gender presentation as always being in alignment and falling into only one category. Because of this, the traditional definitions of gender have ceased to connect to the reality of the identities, expressions and roles of men and women. Not everyone who was assigned male lives as a man, and not everyone who was assigned female lives as a woman.

As body-based definitions have fallen out of step with people’s identities and lives, our intuitions about what makes a man or a woman have failed us. Just as the previous model provided an apparently easy way of classifying men and women for physical, legal, and sexual purposes, the breakdown of that model has implications for all of these areas. When the beliefs of the past collide with the reality of the present, we find ourselves faced with unexpected and confusing results, many of which turn out to be sheer nonsense.

Recently, 16-year-old Ashlyn Parram was told that she could not take her GCSE exams unless she changed into a boy’s school uniform. When she provided the headmaster with a copy of the UK’s Equality Act, which prohibits such discrimination against transgender people, she was made to sit 40 feet away from the rest of the students. Were it not for her personal medical history, which presumably was not scrutinized in the case of any other students, there would have been no clear reason to see this girl as anything other than a girl. There would be no obvious cause to single out this one girl and demand that she must wear a boy’s uniform or sit apart from everyone else.

Here, the adherence to definitions of gender based on bodily history and birth-assigned sex has led to the plain absurdity of treating a girl who identifies, presents, and lives as a girl as if she were something other than female. And in their haste to stop someone they saw as a boy from wearing clothes designated for girls, they very nearly ended up putting a girl in clothes designated for boys. Their insistence on rigid definitions disconnected from the reality of gender would have led to a situation much like the one they initially sought to prevent. Confronted with the dilemma of either recognizing that anatomy and medical history aren’t the final word on gender, or actively mandating cross-dressing, they seemingly preferred cross-dressing.

Similar problems arise from the opposition to laws which prohibit discrimination on the basis of gender identity in public accommodations. Such ordinances have commonly been derided as “bathroom bills”, and campaigns against them unfailingly rely on the alleged threat of “men in women’s restrooms”. The “men” they seek to keep out of women’s restrooms are typically transgender women, as viewed through the model of gender which regards assigned sex as definitive. In one of the most notable examples of such campaigns, the Massachusetts hate group MassResistance covertly filmed several trans women entering the women’s restroom at a convention, which they described as “the insanity that will descend on all of America… unless this sexual radical movement is stopped”.

But let’s suppose that the people fighting against these bills did get their way on this, and everyone was required to use the restroom matching their sex as assigned at birth. What would happen? Not only would trans women have to use the men’s room, but trans men would have to use the women’s room. MassResistance would have a field day: they’d get to see actual men going into the women’s restroom. Is that really the result they’re looking for – male-identified, male-presenting men walking into the women’s room? If they didn’t know these men were trans, it would be “sexual radical insanity” all over again.

Certainly they might profess to believe that gender is fixed at birth and forever unalterable, but when faced with the real-life outcome of their desired policy, they could very well reconsider whether this is a good idea. In seeking to prevent men from using the women’s room under their narrow model of gender, they would actually be forcing men into the women’s room in reality. Again, when given the choice between updating their understanding of gender, or imposing an outdated model upon a world it no longer fits, they’d rather create the same issue they thought they were trying to prevent: there would be both men and women in the men’s room and the women’s room.

Many jurisdictions have placed themselves in a similar situation by both banning same-sex marriage and either refusing to recognize changes of gender legally, or first requiring people to undergo major surgery. As a result, a trans woman who’s still legally considered male is actually banned from marrying men, and can only marry women. For trans people whose genders are unrecognized, same-sex marriage isn’t prohibited at all – in fact, it’s their only option. This probably isn’t what was intended by people who oppose both marriage equality and legal changes of gender, but there’s really no way around it: for the intent of a ban on same-sex marriage to be applied to trans people, you first have to recognize their actual gender.

How we define gender is obviously relevant to our understanding of sexual orientation as well. For instance, people have often wondered how a cisgender woman could have a relationship with a trans woman who has male genitals, and identify as a lesbian nonetheless. The question itself assumes a definition of gender that relies exclusively on anatomy and assigned sex: lesbians are women who prefer women, but someone with male genitals can’t be a woman, therefore a woman partnered with someone who has male genitals can’t be a lesbian.

Under a model of sexual orientation centered on assigned sex, this logic is certainly valid. But how well does it reflect the reality of people’s sexual identities, preferences and behaviors? This assigned sex model defines straight men and gay women as being attracted to cis women and trans men because of their anatomical similarities, and defines gay men and straight women as being attracted to cis men and trans women. While it may be internally consistent, it doesn’t account for the actual patterns we observe in sexual orientation.

If the identities of gay and straight were used to refer to the definitions of this proposed model, we would expect gay men whose partners are trans men to prefer cis women and have an ongoing pattern of relationships with them as well, simply due to their anatomy. Likewise, we would expect that lesbian women whose partners are trans women would also consistently enjoy relationships with cis men, and straight men whose partners are trans women would commonly have relationships with cis men as well.

But this is generally not something we see happening in reality. Straight men and lesbians do not have relationships with men, but with women, and their inclusion of trans women as partners is consistent with that, not contrary to it. The use of “straight” and “gay” in a purely anatomical sense does not help us to understand the true sexual proclivities of the people who identify as such, because that just isn’t what they’re talking about. A woman who primarily prefers women is a lesbian, regardless of the details of her partner’s genitals, because trans women are women. Here, the flaws in traditional definitions of gender can compromise our understanding of sexual orientation as well – but updating our concept of gender provides clarity.

Ultimately, the strict adherence to archaic models of gender often seems to be self-defeating. By insisting that men will always be men and women will always be women no matter what, its proponents have made their own categories of “man” and “woman” increasingly meaningless for practical purposes. When so many women would be considered “men”, what does saying that someone is a “man” by this definition even tell us? Their terms for people’s genders no longer describe people’s genders.

While their use of that word may have once been exclusively attached to certain traditionally “manly” roles and expressions, they’re now using it to mean almost any kind of identity and presentation of someone who was assigned male at birth. There’s nothing wrong with decoupling our destinies in life from our genders, of course – but if that was their intention, I doubt they would be so strenuously insisting that I’m “really a man”. And while many regard such accusations as deeply offensive, I’m more inclined to see them as simply being wrong. They’re just victims of their own conceptual confusion.