****Note: this was actually written several days ago. I wanted to let this settle for a few days and see if I still felt the same way about the incident before publishing it. It still hurt deeply after several days so I published it today.****

I've just had my first run-in with a viewpoint that hurt me deeply. As the parent of a trans teenager, I have expected this to happen and have been educating myself with facts and working very hard at understanding the culture in order to educate those who don't understand. What I didn't expect is that this encounter would come from a friend and ally. I know that she did not intend to hurt me or belittle the world in which we find ourselves, but she did. I'm now shaking as I write this with tears of anger, hurt and humiliation running down my face.

We were having a discussion about C's chosen pronouns and this friend mentioned that she and her son had come up with a gender neutral pronoun. They combined "Man" and "Her" and came up with Mer. I mentioned that there are, in fact, many people who chose to use gender neutral pronouns like "it/its/itself" and "they/theirs/themself" and it's important to use their preferred pronouns. She rolled her eyes. She actually rolled her eyes. Then she said, "Well, that's ridiculous. There are only two genders, genotypically, so they can only be one or the other." I explained that, first of all, there are only two "universally" recognized genders but, in fact, there are more than just XX and XY. Additionally, the physical body is not the only indicator as research has shown that trans people's brains more closely resemble the brains of the gender with which they identify than the gender they were assigned at birth. She stated "It's about chromosomes. Genotypically they're either male or female. If they have Y chromosomes, they're male." I tried, very badly, to defend my stance. I reminded her that as cis people we are in a position of privilege and so we assume that everyone should follow the labels we have. But I have discovered so much more out there in the world through this process - non-binary, trans, etc. and that male and female just aren't enough now. We should try to accept people's own definitions of themselves. It does us no harm at all to validate others. I suggested she spend a bit of time in our world before she makes these proclamations. But she wasn't interested - not in the slightest. I even tried to explain that there was a time when white people used genetics to defend their positions as bigots and racists. When the majority refuses to consider issues faced by a minority, there's a problem. Recognizing that imbalance is essential to progress.

Thankfully our conversation was interrupted by someone who doesn't know the situation so we shifted topics and I left holding back tears. I felt like my child's world was completely belittled. This friend was telling me she knew more about this world because she has a science degree. She was telling me that my daughter and her friends just need to stop being so tricky, to stop making others conform to their standards that don't make sense anyway. I'm heartbroken. If I can't have this conversation with an accepting friend, what chance is there?

I've gone back to review all the information I've found over these past weeks to arm myself for future encounters. I cannot find one that I originally located about the links to chromosomal differences, which was this friend's specific argument -- chromosomes make you male or female -- but I'll keep looking. In the meantime, this little article does a great job of explaining it: http://www.popcrunch.com/if-you-think-biology-is-anti-transgender-you-dont-know-biology/. I think I may send it to my friend. If I get the courage.

Articles and scientific reviews:

http://www.nature.com/nature/journal/v378/n6552/abs/378068a0.html

"TRANSSEXUALS** have the strong feeling, often from childhood onwards, of having been born the wrong sex. The possible psycho-genie or biological aetiology of transsexuality has been the subject of debate for many years1,2. Here we show that the volume of the central subdivision of the bed nucleus of the stria terminalis (BSTc), a brain area that is essential for sexual behaviour3,4, is larger in men than in women. A female-sized BSTc was found in male-to-female transsexuals. The size of the BSTc was not influenced by sex hormones in adulthood and was independent of sexual orientation. Our study is the first to show a female brain structure in genetically male transsexuals and supports the hypothesis that gender identity develops as a result of an interaction between the developing brain and sex hormones5,6."

http://www.ncbi.nlm.nih.gov/pubmed/10843193

"Transsexuals** experience themselves as being of the opposite sex, despite having the biological characteristics of one sex. A crucial question resulting from a previous brain study in male-to-female transsexuals was whether the reported difference according to gender identity in the central part of the bed nucleus of the stria terminalis (BSTc) was based on a neuronal difference in the BSTc itself or just a reflection of a difference in vasoactive intestinal polypeptide innervation from the amygdala, which was used as a marker. Therefore, we determined in 42 subjects the number of somatostatin-expressing neurons in the BSTc in relation to sex, sexual orientation, gender identity, and past or present hormonal status. Regardless of sexual orientation, men had almost twice as many somatostatin neurons as women (P < 0.006). 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."

http://www.jneurosci.org/content/22/3/1027.long

"Gonadal steroids have remarkable developmental effects on sex-dependent brain organization and behavior in animals. Presumably, fetal or neonatal gonadal steroids are also responsible for sexual differentiation of the human brain. A limbic structure of special interest in this regard is the sexually dimorphic central subdivision of the bed nucleus of the stria terminalis (BSTc), because its size has been related to the gender identity disorder transsexuality. To determine at what age the BSTc becomes sexually dimorphic, the BSTc volume in males and females was studied from midgestation into adulthood. Using vasoactive intestinal polypeptide and somatostatin immunocytochemical staining as markers, we found that the BSTc was larger and contains more neurons in men than in women. However, this difference became significant only in adulthood, showing that sexual differentiation of the human brain may extend into the adulthood. The unexpectedly late sexual differentiation of the BSTc is discussed in relation to sex differences in developmental, adolescent, and adult gonadal steroid levels."

http://www.pinktherapy.com/portals/0/CourseResources/Aetiology.pdf

"The androgen receptor (AR), also known as NR3C4, is activated by the binding of testosterone or dihydrotestosterone, where it plays a critical role in the forming of primary and secondary male sex characteristics. Hare et al. found that male-to-female transsexuals were found to have longer repeat lengths on the gene, which reduced its effectiveness at binding testosterone.[18]

A variant genotype for a gene called CYP17, which acts on the sex hormones pregnenolone and progesterone, has been found to be linked to female-to-male transsexualism but not MTF transsexualism. Most notably, the FTM subjects not only had the variant genotype more frequently, but had an allele distribution equivalent to male controls, unlike the female controls. The paper concluded that the loss of a female-specific CYP17 T -34C allele distribution pattern is associated with FtM transsexualism.[19]

In a first-of-its-kind study, Zhou et al. (1995) found that in a region of the brain called the bed nucleus of the stria terminalis (BSTc), a region known for sex and anxiety responses, MTF transsexuals have a female-normal size while FTM transsexuals have a male-normal size. While the transsexuals studied had taken hormones, this was accounted for by including non-transsexual male and female controls which, for a variety of medical reasons, had experienced hormone reversal. The controls still retained sizes typical for their gender. No relationship to sexual orientation was found.[20]

In a followup study, Kruijver et al. (2000) looked at the number of neurons in BSTc instead of volumes. They found the same results as Zhou et al. (1995), but with even more dramatic differences. One MTF subject who had never gone on hormones was also included, and who matched up with the female neuron counts nonetheless.[21]

In 2008, a new region with properties similar to that of BSTc in regards to transsexualism was found by GarciaFalgueras and Swaab: the interstitial nucleus of the anterior hypothalamus (INAH3), part of the hypothalamic uncinate nucleus. The same method of controlling for hormone usage was used as in Zhou et al. (1995) and Kruijver et al. (2000). The differences were even more pronounced than with BSTc; control males averaged 1.9 times the volume and 2.3 times the neurons as control females, yet once again, regardless of hormone exposure, MTF transsexuals lay within the female range and the FTM transsexual within the male range.[25] Phantom limb syndrome is a common, often painful experience after the loss of an external organ. Ramachandran (2008) found that while nearly two thirds of non-transsexual males who have a penis surgically removed experience the sensation of a phantom penis, only one third of MTF transsexuals do so after sex reassignment surgery. Perhaps more remarkably, two-thirds of FTM transsexuals reported the sensation of a phantom penis from childhood onwards, replete with phantom erections and other phenomena.[29]"

http://transcience-project.org/brain_sex.html

"The first study of its kind was conducted by Zhou et al (1995)[1]. The study found sex a-typical differences in the stria terminalis of the brain stem when studying transgender subjects.

A follow up study by Kruijver et al (2000)[2] confirmed the findings and provided greater insight.

The central subdivision of the bed nucleus of the stria terminalis (BSTc) is sexually dimorphic. On average, the BSTc is twice as large in men as in women and contains twice the number of somatostatin neurons. These numbers do not appear to be influenced by sexual orientation or hormone replacement therapy - and both were controlled for by Zhou and Kruijver.

A paper by Chung et al (2000)[3] studied how the volume of the BSTc varied with age in both male and female subjects. They found that the dimorphism was only prevalent in adulthood. Suggesting that the differences found by Zhou and Kruijver are not a cause of gender dysphoria but rather a result.

In Luders et al. (2009)[4], 24 trans-women who hadn't started hormone-replacement therapy were studied via MRI. While regional grey matter concentrations were more similar to men than women, there was a significantly larger volume of grey matter in the right Putamen compared to men. As with many earlier studies, they concluded that gender dysphoria is associated with a distinct cerebral pattern.

In contrast, Savic et al (2011)[10] did not find any sex a-typical differences in the Putaman, or other investigated areas of the brain. They did however find differences between their trans-women group and both the male and female controls.

Two studies by Rametti et al (2011)[5][6] looked at white matter differences in both trans-men and trans-women.

In their study of trans-men they found that control males have significantly higher fractional anisotropy values (FA is a measure often used in diffusion imaging where it is thought to reflect fiber density, axonal diameter, and myelination in white matter) than control females "in the medial and posterior parts of the right superior longitudinal fasciculus (SLF), the forceps minor, and the corticospinal tract".

Compared to control females in the study, trans-men "showed higher FA values in posterior part of the right SLF, the forceps minor and corticospinal tract. Compared to control males, trans-men showed only lower FA values in the corticospinal tract."

The study concluded that there was evidence for an inherent difference in the brain structure of trans-men.

In their study of trans-women they found that trans-women "differed from both male and female controls bilaterally in the superior longitudinal fasciculus, the right anterior cingulum, the right forceps minor, and the right corticospinal tract." The nature of these differences suggests that some fasciculi do not complete the masculinization process in trans-women during brain development.

Berglund et al (2008)[7] demonstrated that brain activation in trans-women was similar to female controls (and dis-similar to male controls). The researchers' conclusion was, that in terms of pheromone activation, trans-women occupy an intermediate position with predominantly female features. The paper further speculates that the cause for the observed differences may lie in the structure of the hypothalamus.

Garcia-Falgueras and Swaab (2008)[8] investigated the hypothalamic uncinate nucleus, which is composed of two subnuclei, namely interstitial nucleus of the anterior hypothalamus (INAH) 3 and 4. They showed for the first time that INAH3 volume and number of neurons of trans-women is similar to that of control females. The study also included analysis of a single trans-man who also had a INAH3 volume and number of neurons within the male control range.

An interesting study by Schöning et al (2010)[9] found that male controls exhibited significantly greater activation of the left parietal cortex when performing mental rotation tasks, in addition they found that trans-women (both those who has started hormone replacement therapy and those who had not), exhibited strong activation in the temporo-occipital regions in comparison to controls males."

**Please note transsexual is often viewed as a slur among the transgender community.