Let’s Talk Biology Again

I’ve discussed this before, in bits and pieces, here and there, now and again. But perhaps it’s wise to assemble all this under one roof where it can be easily referenced.

Approximately 1 in 15000 females, at birth is XY. They are females with female genitals, the works. XY does not mean male. Of these, 1 in 80,000 is Swyer’s Syndrome, and 1 in 20,000 has complete androgen insensitivity syndrome. Another subset has partial androgen insensitivity syndrome and estimates of those born female vary greatly there, from 1 in 20,000 to 1 in 50,000. The cumulative numbers for these three groups are generally assessed at 1 in 15,000, but the frequency could be even higher. The vast majority of XY females are sterile, but rarely some are not, as documented in this study.

1 in 20000 males at birth is XX, also called de la Chapelle syndrome. They are males with male genitals. XX does not mean female. However, the frequency of XX males where the SRY gene crossed over from the Y chromosome to the X may be even higher than that, as this study suggests SRY gene crossover happens more often than previously suspected.

1 in 600 children is XXY, Klinefelters. For the longest time, doctors assumed XXY were always male, because only XXY males had fertility issues, until some biologists decided to go look. And suddenly they found lots of XXY females. This breakthrough came in the last decade so it is relatively “new” news and not all doctors may have heard this year.

The above situations are all scientific facts and prove, conclusively that sex and gender are not determined solely by 5th grade biology lessons about XX and XY, which were simplified for you because at that point in your life, you couldn’t have handled the complexities involved.

So what determines sex and gender? What sex is a male soldier who loses his legs and genitals to an IED. It’s all gone. He has no testicles, no penis, so what sex is he? Stupid question, isn’t it?

It’s stupid because sex and gender are determined in the brain, specifically in the white matter structures of the brain.

Every fetus starts out female and stays female until week 8. That’s when sexual differentiation begins.

The brain is the first human organ to sexually differentiate. This occurs between weeks 8-16. The fetus doesn’t even have genitals until week 14 and then it’s only the unisex “genital tuber” which will later become clitoris, vagina, labia, or penis, testicles, and scrotum.

What drives sexual differentiation? Not genes. Not XX. Not XY. What drives sexual differentiation in the fetus is hormones. Males develop as male because they received about 4 times as much testosterone as estrogen. Females develop as females because they receive about 5 times as much estrogen as testosterone. This is another scientific fact. Cry about it all you want but this is what creates sex and gender.

Consequently, if the mother, during pregnancy for some reason has hormonal interactions that change the basic hormonal ratios away from the median described above, you can get a child whose brain develops one way then their body develops another. Not enough testosterone in weeks 8-16 then returning to median hormonal ratios for weeks 16 and onward? Transgender child with a female brain and male body. Too much testosterone in weeks 8-16 then returning to median hormonal ratios for weeks 16 and onward? Transgender child with male brain and female body. Here is the American Medical Association’s 2011 Annual Meeting Presentation on how hormonal ratios can vary and thus produce the entire spectrum of LGBT people. The presentation is about 70 minutes long, but informative, so be prepared to sit and listen.

So why not fix the brain? We don’t know how without killing the patient. Further, “fixing” the brain would likely destroy the entire personality of that person, a severe violation of their personal liberty and autonomy. So what do we do? We fix the body, which turns out to be relatively easy.

This is the reality of what being transgender means. And I, for one, am tired of ignorant people not understanding science and trying to impose their small minded bigotry against transgender people.

Educate yourself. The science is all available if you want to understand it. The American Psychological Association, the American Psychiatric Association, the American Medical Association, and the American College of Physicians all support the above statements, and all support social transition, hormonal therapy, and surgery as the proper treatment for being transgender. The AMA supports hormone treatment and surgery for transgender patients. The American Psychiatric Association supports transition related medical care for transgender people.

Those of you who choose to wallow in ignorance and hate are what drive transgender kids to suicide, not being transgender but being hated by small minded bigots like yourselves.

Grow up, and stop hating. And stop claiming 5000 year old superstitions that you call a “bible” are somehow right when compared to science. The rest of us are tired of your narrow minded, childish, and anti-scientific ways of thinking. Transgender women are women. Transgender men are men. Deal with it.

11 thoughts on “Let’s Talk Biology Again

  1. Excellent post. I have studied XXY over the years. I have long felt that I have virtually all of the characteristics of an KS XXK Mosaic. When I asked my doctor to test for it, he just laughed.

    I’m featuring this post on T-Central.

  2. I am so pleased to have stumbled on you blog, this post, and your previous list. I’m fascinated with the etiology of transgender people like us. I wonder, are there any articles or references on diagnostic tests? As it is now determining that one is trans is so subjective and fraught with emotion, misinformation, and people like Blanchard, Lawrence, etc. Having a definitive test would help a lot I think.

    Thanks again,


    • I am not aware of any diagnostic lists, but I’ve been told that new diagnostic criteria are very very accurate. In the past, children who were considered “gender curious” would be very difficult to separate from children who are really transgender, and thus the 80% desistance myth was born. However, in recent years, I’ve told the new criteria are separating these two groups accurately, and they are now identifying transgender children with very high accuracy, thus there is very little desistance as they get older. These criteria are apparently subconscious cues that differ between the sexes, and a trans girl will show the same subconscious cues as a cisgender girl and likewise for a trans boy and cisgender boy. Using these techniques, they are accurately identifying trans kids as young as two years of age.

      In the sidebar should be a link to my “One Stop Transgender Brain Research List” which includes a few articles about this very topic.

  3. *

    A child wants to understand their world; they may imagine themselves as another person, a tree, a dog, a chair. Acting school teaches their students to imagine the world through the eyes of their character. Those are transient, educational experiences; those individuals do not surrender their inner persona.

    Other transient experiences that children may also seek to comprehend is that of another person of a different sex – by imagining themselves in that role in their culture.

    The trans child and adult encounter those learning experiences same as any other person. At some point, they (okay, ‘we’) come to their own sense of their gender identity same as any other person. The problem they encounter is their eventual realisation that their gender identity is incongruent to their anatomy.

    Perhaps not so scientific, yet equally telling, are three words that continually arose – whether from my numerous counsellors during the past 40+ years or through my own education:

    – insistent
    – consistent
    – persistent.

    Thus, the trans child will present with expressions of insistence, consistence, and persistence in their self identify rather than of those transient experiments we all do throughout life. ‘I AM a girl!’ While I can’t place my self as being any other person, I can only perceive of my gender identity self as female. My ‘insistent’ female identity never diminished from the time of my earliest memory; it ‘consistently’ has been ‘persisting’ throughout my entire life.


    • Agreed, and those three criteria are what therapists look for when discussing this with clients. But the purpose of my article was not to discuss the psychotherapy side of the question, but the neurobiological basis for why a child (and later, adults) continue to feel that way.

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  5. Dear Cara,
    Thank you so much for this post. I’ve tried to follow the link to 2011 AMA slide presentation on how hormonal ratios can vary and thus produce the entire spectrum of LGBT people. It takes me to the site but the slide presentation won’t load. Do you know another source for this presentation?

    I am in therapy, but haven’t begun transition out of fear of losing my wife. I’m looking for information on the pain and anxiety of gender dysphoria and also information, like this presentation, showing the science of why I am transgender and have gender dysphoria and that is something I wouldn’t wish on anyone. Maybe if she understands my condition she will be willing to at least stay for a trial period after I come out to her.

    I wish I could have met you when I lived in Houston (’97-’04).

    Tami Lynn

    • I just checked and it is only partly loading for me as well. I’m not sure if this is temporary or if the presentation has been lost.

      Another resource I maintain is the “One Stop Trans Brain Research List”. The URL for that is at:

      That list is absolutely not exhaustive. It is just a part of the total number of studies that have been done on this topic.

      I don’t really have anything positive to offer about existing marriages. I know that some survive. I had hoped that mine might but it did not. I also learned some things, hard things, about the people I loved and who I thought loved me, but turned out to only care about me so long as I didn’t disrupt their nice placid suburban lives. I wish you luck but I am not the person to ask for advice on trying to preserve your marriage since mine blew up so spectacularly when I transitioned.

      Good luck to you. One thing I can say is that, despite the pain of loss, after working through that, I am happier and more content today as myself than I ever was as the mask that I wore for so many years.


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