Transgender Brains and Mad Scientists—A Question of Identity

Few topics within the contemporary culture wars have generated as much controversy, confusion, and even outright rage, than topics surrounding transgender individuals. From the proper characterization of their gender identities, to their workplace rights, to their place within sports, it seems virtually every facet of their social existence becomes fodder for debate and rife with discord. A perpetual characteristic of the debates surrounding these topics is just how confused everyone seems to be on all sides. Their foes tend to have a childishly simplistic view of sex and gender, which they wrongfully and arrogantly believe is plain fact supported by biological science, and think that anyone who thinks otherwise must be more concerned with feelings than facts. Their would-be friends often seem equally oblivious to the science behind transgender biology, instead preferring to be ecumenical to all perspectives of marginalized LGBT groups, with the result being a way of speaking surrounding these topics that is linguistically clunky, often confusing, and sometimes flatly incoherent.

Of particular importance and centrality, and drawing perhaps the most controversy, is the question of whether we should consider trans people to be the gender they say they are. Are trans women women and trans men men, and in need of medical gender affirming care, or are they hopelessly deluded and in need of some form of psychological treatment? It would do much good, I think, to get a solid handle on some of the relevant basic biological factors at play, then to bring some philosophical tools to the table, so that some light rather than the usual heat can be shed upon certain serious ethical questions involving transgender individuals.

We’ve all heard the cries from members of the anti-trans camp, to the effect of “Facts don’t care about your feelings! There are X and Y chromosomes, and only two biological sexes: XX, and XY. If you’re XX, you’re a woman. If you’re XY, you’re a man, period. It’s basic biology!” Now, the common reply from the pro-trans camp is typically something like “Biological sex is not the same thing as gender.” Now, this is true, but the latter term is confusing for reasons that will become apparent. It also requires some explanation to elucidate the relationship between the two terms and the centrality of the latter to the questions at issue. One important issue is that ‘biological sex’ is itself an ambiguous term. In employing this term, we could mean any of several distinct things that all fall under the umbrella of what one might call ‘biological sex.’ Equivocation amongst them invites confusion, and an understanding of these distinctions is important in understanding what it is to be transgender.

Firstly, there is what could be termed a person’s chromosomal sex, that is, what combination of sex chromosomes a person has. You might think that there are only two possible such arrangements, but you’d be mistaken. In fact, there are far more arrangements of sex chromosomes beyond just XX and XY that occur in humans. The variety of human karyotypes, or combinations of sex chromosomes, includes X (Turner Syndrome), XXY (Klinefelter Syndrome), XXX, XYY, XXYY, XXXY, XXXX, XXXXY, XXXXX, and others. These typically result in intersex or sexually ambiguous phenotypic characteristics.

Secondly, we might talk about reproductive sex, the sex type of the gametes—the haploid cells that combine to form the diploid zygote that becomes the embryo of a new individual in sexual reproduction, which a person produces. In this gametic sense, sex is binary, as there are precisely two types of gametes—sperm and egg. Some people have pointed to this feature of sexual reproduction as a supposed debate stopper, claiming that what makes one a man or woman is simply which type of gametes a person produces, and that’s all that need be said (Bracketing the intersex conditions that involve producing both gametes in a single body).

This, however, widely misses the mark about just what is controversial surrounding trans identity, intersex conditions, and other sex and gender related issues. No one involved in any of the debates surrounding trans issues on either side is primarily concerned with gametes or their role in the sexual reproductive process. They are rather almost exclusively concerned with people, their different sex-related phenotypic traits, and the social expectations surrounding those traits, making this concern with gametes a giant red herring that is irrelevant to most trans issues. It also elides several crucial biological facts that are themselves much more relevant to these issues.

Apropos of the preceding, and most importantly, there is phenotypic sex, or the sex-related bodily characteristics of a fully developed human being, which in almost all cases are what we use to categorize individuals sociosexually. It is important to note that phenotypic sex does not perfectly map to chromosomal sex. XX and XY genotypes usually develop into the typical phenotypes of female and male, respectively, and the atypical chromosomal variants mentioned above often develop into intersex phenotypes, but the typical XX and XY genotypes can also produce intersex phenotypes, due to either other genetic variations or embryological or environmental factors. One such set of conditions involve a person with XY genotype having a genetic insensitivity to androgenic (masculinizing) hormones, which results in the development in an outwardly female phenotype.

Phenotypic sex can itself be broken down into subcategories. There are the outward sexually dimorphic phenotypic characteristics that we typically use to distinguish between typical members of different sexes, e.g. breasts, body shape, fat deposition patterns, genitalia, facial characteristics, hair growth patterns, etc. Then, there are the sexually dimorphic brain phenotypes that lead to various differences in cognitive styles, sexual behaviors, mannerisms, sense of self-identity, etc. between typical human men and women. So we have a distinction between external phenotypic sex and phenotypic brain sex, and the resulting mental properties characteristic of each sex. We can simply refer to this as gender.

At this point, the latter term needs to be further clarified. What I do not mean by ‘gender’ here are certain ancillary things the term has also been used to represent, such as social norms, expectations, and roles associated with each sex. What I’m referring to is mental differences dependent upon sex-differentiated brains. The second sense of ‘gender’ might be in part socially constructed, but the first is simply a biological fact. Conflation of these two senses has made the debate landscape confused. It perhaps would’ve been better to use the term ‘mental sex’ for the biological sense, given the ambiguity of the term ‘gender,’ but the latter is so embedded in the lexicon that to get rid of it one would have to tear down the entire edifice and rebuild anew, and that would invite yet more confusion to an already fraught issue.

In light of the foregoing distinctions, we can understand the science of what it means for a person to be transgender. The biology of human sexual dimorphism has been extensively studied by neurologists, finding that the anatomical structures of certain brain regions differ between typical male and female brains, so that by analyzing these regions of a person’s brain, one can predict the sex of that person to a high degree of accuracy. In light of this knowledge, several studies have been performed looking at these sexually dimorphic regions of the brain in transgender individuals, finding that indeed these sexually dimorphic regions in their brains more closely match those typical of the sex associated with the gender they identify with than those typical of the chromosomal sex or outward phenotype they possess. One study examining a brain region called the bed nucleus of the stria terminalis (BSTc), found that:

“The number of neurons in the BSTc of male-to-female transsexuals was similar to that of the females (P = 0.83). In contrast, the neuron number of a female-to-male transsexual was found to be in the male range. Hormone treatment or sex hormone level variations in adulthood did not seem to have influenced BSTc neuron numbers. The present findings of somatostatin neuronal sex differences in the BSTc and its sex reversal in the transsexual brain clearly support the paradigm that in transsexuals sexual differentiation of the brain and genitals may go into opposite directions and point to a neurobiological basis of gender identity disorder.”

Now, the sample size of this study is quite small, but several such studies, including a previous 1995 study of the same brain region have produced similar findings. Another study from 2011 examining the white matter microstructure in the brains of trans men against that of cisgender men and women as controls, found that:

“the white matter microstructure pattern in untreated FtM transsexuals is closer to the pattern of subjects who share their gender identity (males) than those who share their biological sex (females). Our results provide evidence for an inherent difference in the brain structure of FtM transsexuals.”

Yet another study examining a different sexually dimorphic region of the brain, the interstitial nucleus of the anterior hypothalamus (INAH), found that:

INAH3 volume and number of neurons of male-to-female transsexual people is similar to that of control females. The female-to-male transsexual subject had an INAH3 volume and number of neurons within the male control range…

Again, these and other similar studies have small sample sizes, but the conclusions all point in a single direction to the fact that the structures of sexually dimorphic regions in the brains of transgender individuals are shifted away from what would be expected based on their outwardly presenting phenotypic sex, and towards that of the opposite sex. This gives us a working definition of what it means for someone to be transgender: a person is transgender if their mental phenotypic sex/gender does not match their external phenotypic sex. That is to say, to be transgender is to have a brain closer to those typically found in people with the opposite phenotypic sex. In such individuals, this mismatch can result in a felt sense of gender dysphoria, which can profoundly affect well-being.

With this in mind, we are far better equipped to engage with some of the ethical and social questions often raised in relation to transgender people. Are transwomen women? Are transmen men? The answers would seem to depend upon what the determinant feature of a person’s identity is. Is it the person’s outward bodily features, or the person’s brain and mind that we should look to for the answers to these questions?

A variant of a philosophical thought experiment often brought up in questions of personal identity may help us shed some light on these questions. The setup goes as follows: Imagine two men, Bob and John, are captured by an unscrupulous brain scientist who wishes to perform a trial run of a brain-swap surgical procedure he has been developing. He puts them both under anesthesia, and removes each of their brains, then replaces each of them in the opposite body, so that John’s brain now resides in (what was) Bob’s body, and vice versa. When the two are eventually resuscitated, the scientist calls out Bob’s name, and the person who appears to be John says, “Yes?” the same applies to the converse. We are then invited to consider who is rightfully John and who is rightfully Bob. Overwhelmingly, the intuition most of us have is to take Bob to be the person with Bob’s brain, who of course has Bob’s mind, his memories, his preferences and dispreferences, his unique sense of psychological continuity and self-identity, etc.

Now let us imagine our mad scientist has kidnapped a third victim, a woman named Alice. He repeats the procedure a second time, this time swapping Bob and Alice’s brains with each other. Now when they awaken, each is surprised to find that they have the body of someone from the opposite sex. If we are consistent with our previous intuition, we will say that it is now Bob who has the female body previously belonging to Alice and Alice who has the male body that was Bob’s. Upon realizing what has occurred, Bob is horrified upon seeing his feminine form, protesting “But I am a man!” The same is true for Alice of course. What are we to make in this case? Are Bob and Alice deluded as to their claimed manhood and womanhood? If we are again to be consistent with our former intuitions about self-identity, and we take one’s manhood or womanhood to be a component of said self-identity, then we must say that Bob is indeed a man and Alice indeed a woman, though the former may now be walking around with female sex characteristics and genitals, and the latter with male sex characteristics and genitals.

Given our previous analysis, this is roughly the situation in which trans people find themselves—only it was not brought about by a mad scientist with his brain swap surgery, but by some confluence of genetics, epigenetics, embryology, and environment etc. It is in this sense that trans people really are the gender they say they are—they have brains that are in important ways characteristic of the gender they claim rather than that which would be predicted by looking at either their external phenotypic sex characteristics or their sex chromosome karyotype. Just as our Bob and Alice felt a profound dysphoria by the incongruity of their external body with their own mental sense of self, so too do trans people.

It of course doesn’t follow that trans women and trans men, respectively, are women and men in every possible sense of these terms. Chromosomally, they are not. Phenotypically, they cannot attain the status of a cisgendered person of their gender, though they can come closer to it through medical intervention. They are not reproductively identical to cisgendered people of their gender, either. These other senses are also relevant to certain ethical questions surrounding trans issues, such as how trans people should be included in sport, or how certain reproductive issues particular to their unique situations should be discussed and treated. Nonetheless, in the sense that matters most for personal identity, in their brains and minds, they are similar, and that is ethically relevant to how we ought to treat them as people, and how medicine should treat them for their gender dysphoria.

If one’s brain and peripheral body are mismatched in terms of sex differentiation, and this is a cause for profound psychological distress, there are two options in order to bring them into congruence—change the body or change the brain. At least two factors tell against the latter option. The first is that we simply lack the technology and knowledge to perform such a change in brain morphology, let alone to do so without causing great and irreparable harm. The second is that, as we saw before in our brain swap case, the brain is the seat of the self, not the peripheral body. Even if we could do so, it would seem backwards to change the self to fit the body rather than the converse. It would be as if, upon hearing Bob’s protest against being embodied in Alice’s female body that he is instead Bob, a man, our mad scientist came up with a brilliant new idea. Instead of returning Bob’s brain to his old body, he would instead perform a new nanosurgical procedure on Bob’s brain with the effect that Bob would forget that he was Bob and a man, and instead feel that he is Alice, a woman, and thereby solve the problem. It seems in this case, the mad scientist hasn’t cured Bob so much as he has simply erased Bob’s identity. Similarly, to try to change a trans person’s brain to match their body, rather than the converse, would be to engage in a sort of identity erasure. This leaves the option of changing the peripheral body to more closely match the brain’s sense of gender, which is precisely what gender affirming care does through hormonal and/or surgical treatments.

Aside from such questions of personal identity, there are of course many other questions that have been raised surrounding the social status and ethical treatment of trans people. These include the proper leagues for trans people in competitive sports, whether trans women in particular should be included in spaces hitherto reserved for cisgendered women, designed to shield them from violence perpetrated by male aggressors—places such as womens’ shelters or gender segregated bathrooms and locker rooms, whether having dating preferences for cisgendered people is an unethical prejudice, among other questions. There is also a set of topics that are often lumped into trans issues by people on both sides of the political spectrum which are actually separate issues. These include various political or social ideologies surrounding various theories of gender (often involving the other sense of ‘gender’ and notions of social constructivism), questions about various proposed gender categories, concerns about people claiming to be trans who are not, issues surrounding other gender-norm nonconforming people, etc. Each of these topics deserves in-depth discussion, which is beyond the scope of this article.

What I’ve sought to do here is to clarify certain notions of sex and gender and to shed light on how the neurobiological basis for what it is to be transgender bears upon the philosophical question of the validity of transgender identity claims, and what that says about how they ought to be understood and treated with regard to that identity. In short, because our brains are the primary determinants of our identity, and because brains are sexually dimorphic, i.e. gendered, and because trans brains are shifted toward the gender they claim to be, there is a relevant and important sense in which trans people are just who they say they are.