If your reaction to these tweets is “No they aren’t!” then check yourself, because thats transphobia talking. If your reaction is “That’s not how biology works”, please, stay a while and listen.

Let’s talk about biology, anatomy, and sex. I swear I had this essay already written before Indya’s tweets went viral.

What Makes a Man

If you’ve seen Jurassic Park then you may remember this scene:

All vertebrate embryos are inherently female anyway. They just require an extra hormone given at the right developmental stage to make them male.

In human male fetuses the SRY gene on the Y chromosome initiates a Testosterone surge starting during the 8th week of pregnancy, and then falling off by week 24. This surge is responsible for the development of primary sexual characteristics in the fetus. Genital formation starts around week 10 and becomes identifiable in the 11th week. The strength of that surge affects how strongly the masculinization occurs, and if the surge is not strong enough then the genitals feminize.

If there is an interference in this process then you can end up with the “wrong” bits. Sometimes this is a partial formation and you get intersex people, but we’re starting to discover that an unknown percentage of the population experienced this fully.

In 2015 an XY woman who was born without ovaries successfully carried and gave birth to a child via IVF. The condition is known as Swyer Syndrome, and usually results in completely non-functional ovaries, but in 2008 a woman was found with Swyer Syndrome who had gone through puberty, menstruated normally, and had two unassisted pregnancies. Her condition went undiscovered until her daughter was was found to also have it.

The fact is, the vast majority of the population has never been tested for karyotype, so we don’t know how common these cases actually are. Where does this come into affect for gender identity? Well, the exact same process occurs for the brain.

The prenatal brain doesn’t really start to develop until between week 12 and 24. The cerebral cortex, the thin outer layer of the brain that contains most of what we think of as consciousness, grows substantially during those periods of time. Prior to that, the structure present is more like a scaffolding, the basic parts of the nervous system necessary for bodily function. The primary sulci (the wrinkles in the cerebral cortex that allow for more surface area) start to form at week 14, well after the genitals have developed.

Boy Interrupted

It has been confirmed multiple times via MRI studies that there are small but significant differences between cis male and cis female brains, differences which align with the gender identities of trans people in the study. Note, this does not mean that anyone with those differences will have that gender, because gender identity isn’t that simple, but it provides evidence that there is a clear difference in masculine and feminine brains.

A change in the testosterone levels in the fetus after the 11th week can directly impact the masculinization of the cerebral cortex, as well as changes in other parts of the brain structure. This has been examined over and over again in studies of female assigned children with CAH (congenital adrenal hyperplasia) and CAIS (complete androgen insensitivity syndrome).

We found a significant relationship between fetal testosterone and sexually differentiated play behavior in both girls and boys.

Fetal Testosterone Predicts Sexually Differentiated Childhood Behavior in Girls and in Boys

An excess of testosterone in the mother’s body during the second trimester can (and does) cause masculinization of the brain in an externally female fetus, and an interference in testosterone production or uptake can (and does) cause feminization of an externally male fetus.

Gender is biological.

What Goes Around Comes Around

Now, here’s the kicker, it doesn’t have to take an external influence to cause this to happen. Last year a fairly large study of transgender individuals found several key genes which were statistically more likely to be longer among trans women (longer, as in having more repeated fragments). Individually these genes may not have an impact strong enough to cause a malfunction of masculinization, but collectively they absolutely could reduce the ability for the fetal brain to masculinize. These genes are all passed from parent to child, giving credence to a tendency for trans parents to have trans children.

Content Warning: Suicide

My family on my fathers side has a long history of mental health problems. My great grandfather is listed in his obituary as having died from a long battle with illness, but within the family it is known that he committed suicide. My grandfather one day, while working in the field alongside my father, one day suddenly fell over and said to him “I’m going to die now.” Our belief is that he intentionally overdosed. One of my uncles spontaneously locked his son in the house, went out to the garage, and shot himself in the head, seemingly out of the blue. I have another uncle in prison after a psychotic break, and his son is also in prison for substance abuse. My aunt experienced a dysphoric breakdown after her first pregnancy, refusing to believe the children were hers or that she ever had even been pregnant.

And then there’s my dad, who I have written about here before. Intensely misogynistic, of the “women belong in the kitchen” variety. I remember having to listen to him rail on about how women were the source of all of the woes of the world. His attitudes remind me extensively of those expressed by MRAs and MGTOWs. He has demonstrated clear signs of depression and disassociation, and in recent years appears to have developed Dissociative Identity Disorder, as he now believes that he hears the voice of God. To me, all of this point to signs of repressed Gender Dysphoria.

After my uncles death, his widow invested considerable effort into studying what could have been the source of his sudden depression. She was the one who learned most of this history and then passed it on to my mother. With this family knowledge came a warning: “Watch your son.” She eventually learned that there was a gene passed through the family line that expressed itself in the males, but my mother and I have not learned what specific gene that is. I’m betting it’s one of the genes described in the above article.

My gender is genetic!

There are, of course, numerous social influences which can have an impact on gender identity, but those largely have an affect on the awareness of gender, not on its existence. The vast majority of trans people were not directly aware from childhood that their sex does not align with their gender. They just know something is wrong (some don’t even know that), and without the language to quantify that wrongness they have no idea the source of the problem. Or, they may know the problem, but feel like they have no options to change it. I did not know I was trans until that night in 2017 when I finally learned that it was possible.

And even still, just because a person’s brain manifests with these traits, that does not mean that their internal gender aligns, because there’s still so many other factors to the brain that medical science has no understanding of. That’s what science is, though! We observe the world, we make predictions, and we test those predictions until the results prove we’re wrong. Science changes, and 200 years ago the idea of someone taking hormones to change their sexual characteristics was so foreign that it wasn’t even fantasy!

Anatomy of a Shapeshifter

Chart of my hormone levels over the last two years.It has been 656 days since I started hormone therapy. Now, it took a month for my levels to normalize, so for practical purposes that means that I have been hormonally female for about 620 days. My testosterone fell to female normal levels almost immediately, and my estradiol has been over 100 pg/mL since my first blood test (cis female normal range is 30-400, varying across the menstrual cycle). In September of 2017 I was practically at pregnancy levels after switching to a much too strong dose of Estradiol Valerate. This has had significant effect on my secondary sexual characteristics.

Some of these are extremely obvious: breast development, fat migrations from my waist and upper torso into my hips and butt, hair and skin changes. My hands and feet have shrank. My pelvis has rotated, making me shorter by an inch and a half and increasing the curve of my back. I’ve lost _so much strength_, and can barely lift the packs of water bottles that we buy at the store (I used to heft two at a time). Jars have become my nemesis.

Changes that aren’t obvious: My prostate has shrank from the size of a golf ball down to roughly an almond, equivalent to its AFAB analog, the skene’s gland. This has eliminated my prostate cancer risk. I have erogenous zones now, and my libido & sexual attraction has changed significantly, manifesting now as a tightness in my abdomen and an ache in my chest, where previously it was entirely centered in the genitals. My sense of smell has dramatically improved, not always for the better (male body odor is so disgusting, and it carries way too far). I feel temperature extremes much stronger, alternating from feeling cold all the time to sweltering in my own flesh. I sweat differently now. Even my bone structure will change over time.

Medically, my body is identical to a post-hysterectomy cis woman, save for the construction of a few bits of soft tissue, and even those have feminized significantly since my orchiectomy. When I have blood work done, I am tested as a woman. For anything not having to do with my reproductive organs, I am treated just like any other woman.

The reality is that humans are not sexually dimorphic. The vast majority of traits that we associate as male or female are entirely flexible and dynamic. Biology is the physiology, behavior, and other qualities of a particular organism, and all aspects of this organism now align female.

I am biologically a woman, and that’s just science.

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