Transgender identity has been in the news lately—and unsurprisingly so. The charged political climate of this month has yielded many contentious issues about gender and LGBT rights to use public restrooms—and it’s clear that these discussions are long overdue. But before we delve and expound on whether transgender individuals like Gretchen Diez should be allowed to use the ladies’ bathroom, it is important for us to set aside our eons-old assumptions about sex and gender. We must first assess our knowledge on the topic because there are so many misconceptions being peddled by netizens about their biological underpinnings. It’s a complicated subject, to say the least, because the science of sex and gender occurs at the intersection of many biological disciplines, including molecular biology, genetics, neurobiology, endocrinology and evolutionary biology.
First, let’s talk about sex. The word “sex” is perhaps one of the most complex words in science and it has a broad range of meanings defined by biology. I am not here to talk about sexual intercourse but more about the science of sexual determination system, sexual differentiation, or how biological sex is coded or programmed during development. Another point to consider is what it means to be male or female. Is gender determined by chromosomal sex, genetics, anatomical features, or behavior? What about sexual orientation and transgender identity? Is sexual orientation determined by experience in childhood or neuroanatomical features and genetic makeup? Does gender live in the brain? These are challenging questions and I will try to answer them all by looking first at the basic biology of sex and gender.
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The ABC’s of XX, XY, and SRY
The science of sex and gender is provisional at some level. We thought that gender was static; now we know it’s dynamic and complex. We were all taught in school that sex is supposed to be simple and immutable—at least at the cellular or molecular level—and an examination of the venerable XY determination system is instructive. As virtually everyone learned in grade school or high school biology, the explanations that appear in our textbooks is that, within the nucleus of every human cell, DNA provides a person’s blueprint—all the information needed to build an individual. And the classic recipe was simple: Females have two X chromosomes, an X chromosome from mom and an X chromosome from dad, while an X chromosome from mom and a Y chromosome from dad will yield a genetic male. When eggs meet sperm, each parent contributes 22 non-sex chromosomes and one-sex chromosome—always an X from the mother, and either an X or Y from the father. Thus, the contribution from the father determines the sex of the baby because the defining gene for male genotypic and phenotypic sex is found on the Y chromosome: a single gene that is commonly called SRY (an acronym for sex-determining region of the Y chromosome, which codes for a protein called testis-determining factor (TDF). The TDF/SRY gene product is the sole determinant for establishing male gonadal tissues that yields a male phenotypic sex.
It seems like a pretty simple and straightforward system—but it wouldn’t be biological science without exceptions and extra rules muddying the waters. Now we know that it becomes increasingly crystal clear that a pair of chromosomes do not always suffice to distinguish girl/boy—either from the standpoint of sex (refers to the biological traits male and female) or of gender (social and cultural attributes traditionally attached to sex). It’s well established in science that, in most instances the XX genotype leads to the development of female sex organs such as uterus, ovaries, fallopian tube, cervix, clitoris, labia and vagina; the XY genotype typically leads to the development of testicles, vas deferens, seminal vesicles, penis and scrotum. In few instances, however, the XX determination system follows an atypical trajectory that muddles the waters i.e., XX yields to the development of male phenotype and XY leads to the development of female phenotype.
Mismatches Between Chromosomal Sex and Hormones
Humans are conditioned by society to view sex and gender as binary attributes or linear spectrum. Before most infants are named, they are assigned a sex based on the appearance of their external genitalia by a third party and we are definitely labeled “boy” or “girl”. Yet the modern science of sex and gender points to a much more ambiguous reality. Determination of biological sex is now getting enormously complex and intricate, involving not only anatomy but a combination of genetic, enzymatic and hormonal factors that unfolds over time. For example, intersex individuals like the guevedoces or colloquially referred to as “testes-at-12” in Dominican Republic and Haiti—those for whom sexual development follows an atypical trajectory because of consanguineous pedigrees—are characterized by a diverse range of conditions, such as 5-alpha reductase deficiency in the embryonic genitalia and maintenance of another in the brain yields . These conditions and the pathways they follow add additional layer of complexity on the gender with which a person identifies does not always align with the sex they are assigned at birth, and they may not be wholly with male or female. As infants and children, the genitalia of these individuals resemble those of females more than males because of the enzyme deficiency. At puberty, the surge of androgens the clitoris enlarges to a penis and the testes descend, changing these individuals into phenotypic males.
The case of guevedoces is proof that chromosomal sex, phenotypic sex, and gender are not always aligned, and genetic differences in humans challenge the usual definitions of female and male. Because hormones, not chromosomal sex, largely determine the sexual characteristics of the nervous system, it is possible to have genetic males with female brains and genetic females with male brains. It is also possible to have female phenotypes despite having XY genotype or male phenotypes with XX genotype.
There are also various conditions in which normal sex differentiation does not occur. For example, in androgen sensitivity syndrome (also called testicular feminization), the genotype is XY and testes are present, but the phenotype (external genitalia and vagina) is female. It is caused by a mutation in the androgen receptor gene. Hence, genetic males (XY) who carry a defective androgen receptor gene may have profound androgen insensitivity because the androgen receptor gene is on the X chromosomes; males thus have only one copy of it, and males with the defective gene cannot produce functioning androgen receptors. In a nutshell, the person with androgen insensitivity syndrome is missing the androgen receptors and without these receptors the physical features will be adversely affected. The testosterone will not be detected by the pituitary gland and thereby can’t detect the negative feedback. Luteinizing hormone (LH) will go up and testosterone will continuously go up which causes increased production of estrogen due to the negative feedback mechanism. These individuals develop normal and functional testes and produce ample testosterone, but they appear outwardly female because their tissues cannot respond to androgen; they have a vagina, a clitoris and labia, and at puberty they develop breasts and a female body shape. They do not menstruate, however, and remain infertile. Androgen-insensitive genetic males not only look like females, but they also behave like them. Even when they are aware of their biological conditions, they prefer to call themselves women; they dress like women, act like women, and they choose men as their partners.
On the other hand, some people have a condition called congenital adrenal hyperplasia (CAH), which literally means overgrown adrenal glands present at birth. The majority of CAH cases are the result of mutations in the gene encoding 21-hydroxylase, an enzyme responsible for synthesis of two additional steroids secreted by the adrenals: cortisol and aldosterone. In XX genotype, CAH leads to overactive secretion of testosterone during development Although they are genetically female, because their adrenal glands secrete unusually large amounts of androgen, CAH females are exposed to abnormally high levels of circulating androgens early in their development. CAH girls often exhibit behavioral traits more often associated with boys than girls; they are more likely to describe their behavior as aggressive or tomboyish. As adults, these women may be more likely to form sexual relationships with female partners.
Gender is neither binary nor linear spectrum
Mounting evidence from clinical studies shows that sex is not an immutable condition determined at birth because there are multifarious factors that play a role into whether someone is male or female, or somewhere in between. But where does the feeling of gender come from in the first place? The science is still far from conclusive because the neuroscience or genetics of gender identity is still in its infancy. Little is known about the causes of transgender phenomenon but scientists have made great strides in recent years in unlocking the biological basis of several factors by looking for genetic and neuroanatomical signs in transgender people. Clinical studies of transgendered individuals show that they report deeply held identities that oppose their genotypic and phenotypic sex. Their experiences, usually thoroughly assessed in rigorous diagnostic evaluation, often lead to hormonal or surgical reassignment of phenotypic sex. Current understanding of transgendered men and women thus reinforces a sense that their perception of sex and sexuality has biological underpinnings.
Scientists often look at twins in studying the genetics of transgender individuals. A major difference between identical and fraternal twins is that the former share more of their genetic material than the latter. If researchers find more agreement in transgender identity among identical twins than in fraternal twins, they infer that genetics play some role. And, in fact, this is exactly what early studies are finding. For example, in one 2012 review of the literature, Ghunter Heylens of Ghent University in Belgium and his colleagues looked at 44 sets of same-sex twins in which at least one twin identified as transgender. They found that in nine of the 23 identical twin pairs, both siblings were transgender, whereas in no case among the same-sex fraternal twin pairs were both twin transgender, suggesting transgender identity has some genetic underpinnings.
Similarly, some neuroscience studies have shown that trans people appear to be born with brain structures that resemble those of the individuals with the same gender identity, rather than people with the same sex at birth. In 1995 and 2000, two clinical studies by independent teams of researchers decided to examine a region of the brain called the bed nucleus of the stria terminalis (BSTc) in trans- and cisgender men and women. The purpose of these two studies sought to look closer into the brains of transgender individuals to figure out if their brains better were similar in neuroanatomical structures to their assigned or chosen sex. Both teams discovered that male-to-female transgender women had a BSTc more closely resembling that of cisgender women than men in both size and cell density, and that female-to-male transgender men had BSTcs resembling cisgender men. What was also astounding was that these differences remained even after the scientists took into consideration the fact that many transgender men and women in their study were taking estrogen and testosterone during their transition by including cisgender men and women who were also on hormones not corresponding to their assigned biological sex (for a variety of medical reasons). These findings have since been confirmed and corroborated in other studies and other regions of the brain, including a region of the brain called the sexually dimorphic nucleus, that is believed to affect sexual behavior in animals.
These findings suggest that gender is certainly neither binary nor linear spectrum. Like many other facets of identity, it can operate on a broad range of levels and operate outside of many definitions. It also appears that gender may not be as static as we assume. At the forefront of this, transgender identity is enormously complex with multicausal causes – it’s unlikely we’ll ever be able to attribute it to one neat, contained set of causes, and there is still much to be learned in the future. But we know now that several of those causes are biological. Most of these individuals are not “choosing” a different identity on a whim. The transgender identity is multi-dimensional – but it deserves no less recognition or respect than any other facet of humankind. Nobel Prize-winning Steven Weinberg once said that the spread of scientific spirit during the Enlightenment in the late seventeenth and early eighteenth centuries was one of the reasons that stopped the burning of witches. Learning the new science of sex and gender may not end mankind’s persistent superstitions and misconceptions but it might help stem the surge of homophobia and transphobia in the country. Lastly, being knowledgeable about sex and gender holds the prospect of helping shape public opinion and policy making to acknowledge this reality.
[Parts of this article were culled from Neuroscience: Exploring the Brain by Bear, et al. and Neuroscience by Purves, D., et al].
11 Replies to “Why the Modern Science of Sex and Transgender Identity Matters for Every Filipino”
Thanks, Mr. Quilon; your website article is too scholarly and too academic; ordinary people like me cannot understand the scientific terms and interactions of the terms. I bet that our leaders, who are mostly in mental average IQs; some are even undereducated; some are on the level of mentally retarded cannot understand, nor comprehend what you want them to understand.
There is a guy, a friend of mine, who is a Hindu from India, who believes in re-encarnation. That is, if you die, and may go “heaven”…you decide to come back again, to further your learning for the development of your soul and being. He believes, that the Planet Earth is a ‘school house’, by which we humans with souls , use as a place of learning.
So, you live today as a man…then you die,,,your soul go to heaven…then you decide to go back to Earth , to further your learning…you go back as a woman. Unfortunately, some of your characteristics as a man were not erased, in your previous mind records…So, you become a man trapped in a woman’s body…
Maybe, this is the case; because no science can still prove that there is a soul. No science can still prove that there is re-encarnation.
Only our religions, tell and teach , terms us such: God, soul, re-encarnation, heaven, hell, afterlife, etc…we still don’t know , why these things happen …I am happy that the Philippines is slowly entering its Age of Enlightenment…it is late, but it is better that nothing.
Thanks to the internet; to the netizens and to the Website bloggers . You are doing a good job !
If reincarnation (https://en.wikipedia.org/wiki/Reincarnation) does exist why does nobody know what we were in a previous life and the life before that?
Wouldn’t it be nice if it is true. On your previous life , you used to be the oppressor, now re-incarnated you are now the oppressed, you use to be rich but now you are poor, you use to be white but now you are black, and if you become aware of your previous life you would wish that you would have done something different to make sure everyone in the future will have a good life.
I’m just saying, there are many issues today that needs to be solve, you don’t want to get re-incarnated( assuming it’s true) in the future where all these issues were never solved.
in case reincarnation does exist, I dont know who decides in what I will return. In my previous life, I may have been a plant, an egg, a tree, a leaf. Or was I a human being (a slave?).
To be honest I have no recollection and I dont believe in reincarnation. What I do know is that I live about 80-90 years on this planet earth and that I have to “create” my own happiness and my own wealth. I myself am just a tiny part in a big machine and only you can make your own life a success (or ruin it). If you come from a poor background, I am really sorry for you (pls blame your parents for that) and pls dont make the same mistakes your parents made (by not procreating while being dirt poor).
In case you are the oppressed then its time laws are changed or pls leave your country.
“I’m just saying, there are many issues today that needs to be solve, you don’t want to get re-incarnated( assuming it’s true) in the future where all these issues were never solved.”
Change a few (or a lot of) laws in PH, migrate to a different country but for sure do not let your kids be in the same situation (so stop procreating).
In the Buddhist religion, especially the Tibetan Buddhism. If the Dalai Lama, die….the way they choose his successor is the have a monk, have a vision of a reincarnated “boy.”..who will succeed the previous Dalai Lama. The monk will have a vision, where they could find this boy; who his parents are…
So, the Buddhist monks will go and search for the “reincarnated boy”…Once they find the “reincarnated boy”. They will test the “reincarnated boy”, with the properties of the previous Dalai Lama…they will ask also about important parts of the departed Dalai Lama’s life…
Once the Buddhist monks are convinced; that this is the “reincarnated Dalai Lama”, indeed. They will take the “reincarnated boy” and raise him as the new Dalai Lama.
I don’t know , if reincarnation is true or not…I, myself, have never have a vision of my previous life. I never felt , I was reincarnated…
Their belief is also: you can be reincarnated as : a dog; a swine; a monkey; a cockroach; a man; a woman; etc..
If in this life you are a man, who rape a woman…in the next life , you will be reincarnated as a woman who will be raped also …most of our Filipino politicians will surely be reincarnated as: monkeys; swines; dogs, or cockroaches…
Some of our Filipino politicians, looks like swines already, even if they are not reincarnated yet !
Thank you for sharing good and important information .. Happy Blogging
Only when Pilipinos gets interested in science. As for now, who cares?
And even if they do get interested in science will they be given the accessibility to learn it?
I’m expecting the next installment to say, yes, while there are exceptions existing to the more common occurrence (i.e., the rules) of male and female, there are hermaphrodites and other oddballs. But they are still the exceptions, and while accommodations can be made for exceptions, they can never be made part of the rule.
But I’m getting ahead and assuming things, so, up to there.
Tang ina, so much pseudo-science and fraudulent jargon to attempt to cover for perverted fetishes. Why must we as society cater to the demented minds of these degenerates? Appeasing outrage from the twitter mob? Call it a day, and call faggots faggots.
No, it does not. The most honest conclusion one can make is simply this: something is wrong with them(trans).
It is the same phenomenon when it comes to extremely high IQ individuals. Almost all of them exhibit a form of autism called Asperger’s Syndrome. And yet we do not arrive to the conclusion that this is a normal expected conditions.
A good amount of study (with consistent conclusions) have shown that it is prenatal hormone exposure that decides gender (https://onlinelibrary.wiley.com/doi/abs/10.1111/j.1467-8624.2005.00843.x).
“The most honest conclusion one can make is simply this: something is wrong with them (trans).”
So what do you want to do with them? Kill them? Heal them? Put them in a mental hospital (from away from people who are NOT wrong)?