If anything, it’s its biggest opponent.
Science offers a unique look at the trans experience through three areas of study: genetics (physiology), neurobiology (psychology) and endocrinology (hormones). The genetic lens looks at biological sex. Most of us learned sometime in middle school that female and male biological attributes are determined by chromosomes X and Y. Individuals with XX chromosomes are female, and individuals with XY chromosomes are male. But the truth is, this isn’t set in stone; like any living system, biological sex has the potential for change.
Intersex individuals, for example, can have any combination of X and Y chromosomes, such as X or XXY. These differences may not even be detectable without chromosomal testing. On the other hand, individuals with XX chromosomes can develop male reproductive organs, and vice versa. During fetal development, cells clump together to form the basis of human sex organs called the bipotential primordium. These cells are neutral, not aligning with male or female characteristics quite yet. After formation, a specific gene from the Y chromosome called SRY may activate. SRY acts to push the bipotential primordium towards developing into male gonads and testes, but it is not yet fully understood. PhD candidate Simón(e) Day, at the NYU Langone Medical Center’s Tsien Lab for Neuroscience, summarizes the function of the SRY gene: “SRY is not a simple on/off switch, it’s a precisely timed start signal, the first chord of the “male gonad” symphony. A group of cells (instrument sections) must all express SRY (notes of the chord), at the right time (conductor?). Without that first chord, the embryo will play a different symphony: female gonads, or something in between.”
As we grow into adulthood, other genes maintain sexual characteristics. Should these genes stop functioning, gonades can physically change to begin displaying characteristics of the ‘opposite’ sex. The waters of biological sex can be muddied further; none of the above genes are directly involved in biological sex! So-called secondary sex characteristics, like penis/vulva behavior and appearance, are all shaped by hormones, environment, and even experience. This is where the neurobiology lens steps in: by looking at the overlap between behavior and biology.
Let’s get one thing out of the way right off the bat: there is no such thing as the male or female brain. By that, I mean there are no scientifically useful observable differences in appearance and chemistry. Essentially, the notion of a gender binary is scientifically useless–and what’s more, trans (cisn’t) people have the brains to prove it. Over the past 50 years, the field of neuroscience has become increasingly interested in studying the transgender brain. These studies have come to some very interesting conclusions. n both pre and post-transitioned individuals (it should be noted here that transitioning is not mandatory for trans people, many choose not to for varying reasons and are still valid). Overall, trans people have brains somewhere in between what is considered the typical “male” and “female” brain, both pre and post transition. In other regions of the brain, pre (and post) transitioned individuals show characteristics which closely resemble the brains of cisgendered individuals with the same gender identity. Further, many transgender brains, often of nonbinary or other identifying individuals, show structures completely different than cisgendered and other trans individuals!
That being said, the idea of a sexually demographic brain is, as I’ve said above, essentially junk science. There are average observable differences in traditionally male or female brains, however these are just averages and the typical “male” and “female” brain structures vary greatly. For instance, the brains of many gay males present more similarly to the female brain than the male, although this is not true for gay females on average. Hormones play a substantial role in the development of the brain and how it interacts with the rest of the body. Therefore, hormones are another key player in understanding the transgender biological and neurological experience. Vasopressin, for instance, is a hormone linked to the differences and similarities between sexes that fall within the widely accepted binary. What causes this hormone to activate in either direction (tending towards male/female) is still unknown.
Separating gender by hormones alone is just as problematic as trying to do it by physiology or brain structure. Everyone has the typically “male” and “female” hormones of testosterone and estrogen respectively active in their body. In fact, for the most part, male and female bodies display similar levels of these hormones, the biggest difference appearing in higher testosterone levels in adult males, typically. But even across the binary, measurements of these sex hormones change so much between individuals, it is nearly impossible to establish an accurate baseline. A recent study suggests that only about 56% of an individual’s testosterone levels can be explained by genetics. Meaning that nearly half of the probability of someone’s hormone levels are determined by external factors. Essentially, even for cis people, there are no “normal” hormone levels, so how could hormones even be used to separate trans individuals?
At the end of the day, the science is pretty clear. Not only is a gender/sex binary wrong, its nearly completely scientifically useless. Scientists have a hard enough time defining what the cisgender brain and body look like because as much as it would be scientifically helpful for humans to fit neatly inside little boxes, that is just not the reality we live in. Humans are complex and unique creatures, no two are exactly the same. It is the differences in humanity that make us so strong as a species and as communities. Transgender people are a reality and not a rare one. They live and walk among us everyday. They have interacted with you, at some point or another. At the end of the day, they are just people, lovers, adventurers, students, teachers, baristas, artists, engineers, parents, pet owners, athletes, scientists, scholars, and siblings, just like any one of us.