When the Brain Refuses Your Categories: Sapolsky and the Neuro-Biology of Transness

3–4 minutes

Looking through some of the drafts clogging the blog, I decided to whittle away at the queue. I started this months ago. It’s here now, not particularly in sync with the season or recent topics, but I like Sapolsky.

‘Biology is destiny’, say the Christian Right, the bland bureaucrats of morality, the loud whisperers at Sunday school. They want gender to be a tomb carved in marble: you’re assigned at birth, and you stay a perfect statue. But Sapolsky waltzes in and says, ‘Hold up – what do you mean by biology? Which biology? Which markers count?’

Video: Neuro-biology of Transsexuality, Prof. Robert Sapolsky

In the clip above, Sapolsky unpacks neurological evidence that upends the essentialist cheat codes. He doesn’t pretend we now have the final answer to gender. He does something scarier to fundamentalists: he shows just how messy biology is.

The Bed Nucleus, the Finger Ratio, and the ‘Wrong Body’ Hypothesis

Sapolsky discusses three pieces of neurobiological evidence:

  1. Digit ratio (2nd vs 4th finger length): In lesbians, on average, the ratio is closer to what you see in straight men than straight women. That’s a correlation, an eyebrow-raiser, hardly a decree.
  2. Acoustic reflexes (auto-acoustic reflex): Another early finding in women’s sexual orientation, though faint and underexplored.
  3. The bed nucleus of the stria terminalis (BSTc): Here we reach heavy artillery. There is a neuron population in this region that, on average, is about twice as large in males as in females. In postmortem analyses of trans women (male → female), this region’s size corresponds to their identified gender, not their natal sex. Crucially, that alignment is seen even in trans individuals who never underwent full hormone therapy or surgical changes.
    • Sapolsky recounts astute controls: men treated (for, say, testicular cancer) with feminising hormones don’t show the same shift.
    • Also, using the phantom-limb analogy: men who lose their penis to cancer often report phantom sensations; trans women rarely do. That suggests the body map in the brain never fully “registered” that organ in the same way.

He doesn’t overclaim. He doesn’t say, ‘Case closed, biology proves everything’. He says: These data complicate your neat categories. They force you to ask: which biological measure do you privilege? Hypertrophied neurons? Chromosomes? Receptor density? Hormones? All of them simultaneously? None of them?

Essentialism as a Trap

Fundamentalists and anti-trans ideologues deploy essentialism because it’s convenient. They demand an ironclad ‘essence’ so they can exclude anyone who fails their test. But what Sapolsky shows is that essence is simply a scaffold; we get to pick which biological scaffolds we accept. They may choose genes and genitals; the neurobiologist gives them neuron counts and brain-maps. When your ideology elevates one scaffold and ignores the others, it betrays its own contingency.

Moreover, the evidence suggests that identity, experience, insistence (in Sapolsky’s language: ‘insisting from day one’), and internal brain structure might converge. The ‘wrong body’ isn’t a metaphor. It’s a mismatch between internal brain architecture and external form. The stubborn fragments of biology that fundamentalists accept are torn by the dissonance that science increasingly reveals.

What This Means for Trans Rights, Discourse & Strategy

  • Science is never ‘conclusive’. Sapolsky offers compelling support, not gospel. Anyone claiming this settles everything has never looked at a scatter plot.
  • Lived experience still matters. Even if we never had brain slices, self-reports, psychology, psychiatry, anthropology, narratives remain valid. Brain studies supplement, not supplant, testimony.
  • Essentialist opponents have boxed themselves in. When they demand biology decides everything, they hand the baton to neuroscientists – and neuroscientists keep running with it. The entire ‘biology’ equals only what I like’ regime is exposed.
  • Ambiguity is a strength, not a liability. If we insist identity is linear and tidy, we re-enact their demand for purity. Recognising complexity, mess, and variance is radical resistance.

The Scourge: They’re Really Fighting Is Ambiguity

A Sequel to “The Disorder of Saying No” and a Companion to “When ‘Advanced’ Means Genocide”

In my previous post, The Disorder of Saying No, I explored the way resistance to authority is pathologised, particularly when that authority is cloaked in benevolence and armed with diagnostic manuals. When one refuses — gently, thoughtfully, or with a sharp polemic — one is no longer principled. One is “difficult.” Or in my case, oppositional.

Audio: NotebookLM podcast on this topic.

So when I had the gall to call out Bill Maher for his recent linguistic stunt — declaring that a woman is simply “a person who menstruates” — I thought I was doing the rational thing: pointing out a classic bit of reductionist nonsense masquerading as clarity. Maher, after all, was not doing biology. He was playing lexicographer-in-chief, defining a term with centuries of philosophical, sociological, and political baggage as though it were a checkbox on a medical form.

I said as much: that he was abusing his platform, presenting himself as the sole arbiter of the English language, and that his little performance was less about clarity and more about controlling the terms of discourse.

My friend, a post-menopausal woman herself, responded not by engaging the argument, but by insinuating — as others have — that I was simply being contrary. Oppositional. Difficult. Again. (She was clearly moved by When “Advanced” Means Genocide, but may have missed the point.)

So let’s unpack this — not to win the debate, but to show what the debate actually is.

This Isn’t About Biology — It’s About Boundary Maintenance

Maher’s statement wasn’t intended to clarify. It was intended to exclude. It wasn’t some linguistic slip; it was a rhetorical scalpel — one used not to analyse, but to amputate.

And the applause from some cisgender women — particularly those who’ve “graduated” from menstruation — reveals the heart of the matter: it’s not about reproductive biology. It’s about controlling who gets to claim the term woman.

Let’s steelman the argument, just for the sport of it:

Menstruation is a symbolic threshold. Even if one no longer menstruates, having done so places you irrevocably within the category of woman. It’s not about exclusion; it’s about grounding identity in material experience.

Fine. But now let’s ask:

  • What about women who’ve never menstruated?
  • What about intersex people?
  • What about trans women?
  • What about cultures with radically different markers of womanhood?

You see, it only works if you pretend the world is simpler than it is.

The Language Insufficiency Hypothesis: Applied

This is precisely where the Language Insufficiency Hypothesis earns its keep.

The word woman is not a locked vault. It is a floating signifier, to borrow from Barthes — a term whose meaning is perpetually re-negotiated in use. There is no singular essence to the word. It is not rooted in biology, nor in social role, nor in performance. It is a hybrid, historically contingent construct — and the moment you try to fix its meaning, it slips sideways like a greased Wittgensteinian beetle.

“Meaning is use,” says Wittgenstein, and this is what frightens people.

If woman is defined by use and not by rule, then anyone might claim it. And suddenly, the club is no longer exclusive.

That’s the threat Maher and his defenders are really reacting to. Not trans women. Not intersex people. Not language activists or queer theorists.

The threat is ambiguity.

What They Want: A World That Can Be Named

The push for rigid definitions — for menstruation as membership — is a plea for a world that can be named and known. A world where words are secure, stable, and final. Where meaning doesn’t leak.

But language doesn’t offer that comfort.

It never did.

And when that linguistic instability gets too close to something personal, like gender identity, or the foundation of one’s own sense of self, the defensive response is to fortify the language, as though building walls around a collapsing church.

Maher’s defenders aren’t making scientific arguments. They’re waging semantic warfare. If they can hold the definition, they can win the cultural narrative. They can hold the gates to Womanhood and keep the undesirables out.

That’s the fantasy.

But language doesn’t play along.

Conclusion: Words Will Not Save You — but They Might Soothe the Dead

In the end, Maher’s definition is not merely incorrect. It is insufficient. It cannot accommodate the complexity of lived experience and cannot sustain the illusion of clarity for long.

And those who cling to it — friend or stranger, progressive, or conservative — are not defending biology. They are defending nostalgia. Specifically, a pathological nostalgia for a world that no longer exists, and arguably never did: a world where gender roles were static, language was absolute, and womanhood was neatly circumscribed by bodily functions and suburban etiquette.

Ozzy and Harriet loom large here — not as individuals but as archetypes. Icons of a mid-century dream in which everyone knew their place, and deviation was something to be corrected, not celebrated. My friend, of that generation, clings to this fantasy not out of malice but out of a desperate yearning for order. The idea that woman could mean many things, and mean them differently across contexts, is not liberating to her — it’s destabilising.

But that world is gone. And no amount of menstruation-based gatekeeping will restore it.

The Real Scourge Is Ambiguity

Maher’s tantrum wasn’t about truth. It was about fear — fear of linguistic drift, of gender flux, of a world in which meaning no longer obeys. The desire to fix the definition of “woman” is not a biological impulse. It’s a theological one.

And theology, like nostalgia, often makes terrible policy.

This is why your Language Insufficiency Hypothesis matters. Because it reminds us that language does not stabilise reality — it masks its instability. The attempt to define “woman” once and for all is not just futile — it’s an act of violence against difference, a linguistic colonisation of lived experience.

So Let Them Rest

Ozzy and Harriet are dead. Let them rest.
Let their picket fence moulder. Let their signage decay.

The world has moved on. The language is shifting beneath your feet. And no amount of retroactive gatekeeping can halt that tremor.

The club is burning. And the only thing left to save is honesty.