by Katherine J. Wu
figures by Daniel Utter
Let’s talk about sex.
Seriously. Not intercourse, though – more about how genetic sex is programmed during development. Sexual identity has been in the news often lately, and unsurprisingly so: the past few years have yielded sweeping reforms in civil rights, spurring new conflicts surrounding everything from age-old battles in gender equality to legislation enforcing anti-transgender bathrooms. It’s a complicated subject, to say the least. With regards to science, we don’t know enough about gender identity to draw any conclusions about its biological underpinnings, and certainly not about what is “right” or “wrong.” We are only now beginning to fully understand how mammalian sexual identity has evolved, and its dependence on the sex determination systems that allow biological development of sexual characteristics in different organisms.
The sex determination we’ll discuss today is (unfortunately?) not the dogged resolve to copulate. Most multicellular organisms, humans included, use sexual reproduction to reproduce. Compared to asexual reproduction, in which cells can simply create carbon copies of themselves, sexual reproduction allows for the introduction of genetic diversity into a population. In most sexually reproducing organisms, there are two sexes – but the ways in which these sexes are determined and the ways in which they manifest vary greatly. What are the ways in which sexual characteristics are encoded? Why are there so many systems for one seemingly common result?
SRY not SRY
We were all taught the classic recipe in grade school: an X chromosome from mom and an X chromosome from dad will yield a genetic female, while an X chromosome from mom and a Y chromosome from dad will yield a genetic male. The XY sex determination system (Figure 1A) is certainly what’s most familiar to us, and it’s used in most other mammals, as well as a few select insects and plants. Briefly, human cells all carry chromosomes, which carry our genes. When egg meets 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[1].
Following fertilization, a fetus begins to develop. At first, its sexual organs manifest as a genderless gonad, or sex gland – basically a small, thick ridge of tissue near what will become the abdomen. The “default” sex (i.e., without any other further input) is actually female – however, the presence of a gene called SRY on the Y chromosome initiates the release of testosterone and the formation of male sex organs. SRY is a transcription factor – a genetic element that can turn on the expression of other genes. In this way, SRY is like the master switch to turn on the suite of “male” genes in a developing organism. Thus, the presence of a single Y chromosome switches on the male pathway, something that is clear in what’s called Klinefelter Syndrome, in which individuals carry two X chromosomes and one Y chromosome, but develop testes and appear generally “male.” Without the presence of a Y chromosome, and thus without SRY, cells secrete estrogen instead of testosterone, and an XX baby develops female sexual organs.
It seems like a pretty clear system – but it wouldn’t be biology without exceptions and extra rules muddying the waters. When it comes to sex chromosomes, X’s and Y’s are not the only ingredients available. Many other sex determination systems exist, and the concept of “male” vs. “female” isn’t quite as simple as humans once thought.
The Birds and the Bees (and Some Other Things Too)
Unsurprisingly, with the immense variation observed in our natural world, more than one sex determination system exists. Ours, XY, is not even predominant. A few key examples tend to predominate: the ZW system in birds, XO in insects, haplodiploidy, and environmental sex determination systems.
The ZW system (Figure 1B) exists in birds and some reptiles, and operates opposite of XY: females get the mixed set of sex chromosomes (ZW), while males are ZZ. Thus, unlike in humans, the mother’s contribution determines the sex of the progeny[2]. Just as the mammalian Y chromosome carries the male-determining SRY, the avian W chromosome carries similar master switches FET1 and ASW, which are necessary for female development of the offspring, which will otherwise “default” to male.
In the XO sex determination system (Figure 1C), which is found in several insects, females are still XX, but instead of carrying a Y chromosome, males simply carry a single X – the “O” in “XO” indicates the absence of a second sex chromosome. Each sperm carries either an X chromosome or no sex chromosome at all – but once again, as in XY, the father’s contribution determines the sex of the offspring.
After this, things start to get a little weirder. Honeybees utilize the system of haplodiploidy (Figure 1D), in which unfertilized eggs (which carry only one set of chromosomes and are thus haploid) develop into males and fertilized eggs (which carry two sets of chromosomes and are thus diploid) develop into females. Importantly, this is distinct from the XO system, where progeny inherit two copies of all non-sex chromosomes, regardless of sex; in haplodiploidy, males inherit only one copy of all chromosomes, sex and non-sex (Figure 2A).
Honeybee colonies typically center around a single fertile queen, serviced by an army of male drones and female workers. The queen lays a vast number of eggs, some of which are fertilized and develop into females. Those that remain unfertilized develop into males. Thus, in this system, males have no fathers and can produce no sons. Furthermore, if a queen chooses only one drone to mate with, all her daughters will share 75% of their genes with each other (unlike in humans, where siblings share 50% of their genes) because they each inherit the full set of their father’s genes, rather than just half. While this system seems vastly overcomplicated, it is believed to have been evolved to promote the social nature of honeybees: as a female worker, it turns out to be more evolutionarily advantageous to protect your sisters (with whom you share 75% of your genes) than it is to produce daughters of your own (with whom you share only 50% of your genes) (Figure 2B). Thus, the community structure revolves around the queen. This is an interesting case where the genetically determined sex of individuals shapes their role within the larger community.
Finally, there exist systems in which sex determination isn’t dependent on chromosomes at all. In alligators and some turtles, the temperature at which the egg is incubated during a sensitive period determines sex: lower temperatures produce females, higher temperatures produce males (the phenomenon of “cool chicks” and “hot dudes”) (Figure 1E). However, this rule does not hold true in every species – sometimes the opposite rule is in effect, or temperatures at either extreme produce one sex, while an intermediate temperature produces the other. Some snails and fish are actually able to reverse sex midway through life, depending on environmental conditions, in a process called sex reversal. Thus, genetic sex is a far more fluid process than one might assume.
The fact that genetic sex can be directed by the flip of a single switch may be surprising. Sex is complex – but then again, there are a lot of other factors at play and, clearly, environment can have a big influence on how sex expresses itself. Additionally, there are many documented cases of humans with a genetic sex that appears “contrary” to their physical appearance. For instance, we know of genetically XX persons who have developed testes and external characteristics of men, and genetic XYs who develop as females. An example of the latter case occurs in Swyer Syndrome, often when there is a mutation in the SRY gene. While the rest of the Y chromosome is left intact, a malfunctioning SRY means that the male “switch” is never flipped, and the indifferent gonads do not get signals to become testes. Swyer Syndrome patients develop externally as female, but do not have ovaries and are infertile.
Finally, inheriting extra or too few chromosomes can considerably alter how sex manifests. Klinefelter is a common example, as well as Turner Syndrome (XO), where a sex chromosome is missing, often leading to developmental defects. Thus, all it takes is a small genetic change to turn SRY, or any of the genes it targets, on (or off).
(De)Generation Y
We know very little about how sexual reproduction and sex determination systems evolved – the theories are, of course, difficult to test. But another important question is, once sexual reproduction did evolve, why did it branch off in so many ways? And, perhaps more pressingly, is it still evolving in ways that could affect us?
The answers are still mostly elusive. There has been some indication that the XY and ZW systems are still connected to a common ancestor, even though they manifested a complete reversal somewhere down the line. One small but interesting line of evidence lies in the platypus, which encodes a whopping 10 sex chromosomes (males are XYXYXYXYXY instead of XY – apparently, size matters to platypodes) that bear great similarity to the bird Z chromosome, but technically operate under XY sex determination rules. Interestingly, though, the platypus Y lacks SRY. Thus, platypodes may end up being the “missing link” between these two systems.
Furthermore, analysis of the Y chromosome has indicated that it probably evolved from the X chromosome, acquiring some literal “man power” along the way. This “differentiation” event solidly distinguished the roles of the two chromosomes, and they began to evolve away from each other over time. In its current state, the Y chromosome is much smaller than the X chromosome, and appears to have lost the unnecessary X genes[3] along the way. Y continues to exhibit signs of this (very, very slow) Y degeneration as time progresses. In fact, the XO sex determination system is believed to have arisen from complete loss of an effective Y chromosome that was ultimately discarded for its relative inefficiency. There’s no need for panic, though, XY readers – your Y chromosome is unlikely to be going anywhere anytime soon, or maybe ever. Complete loss of Y is a pretty extreme event, and much evidence has accumulated that the loss of genes from the Y chromosome will ultimately plateau.
Plenty of Fish (Sexes) in the Sea
Sex determination in humans is fairly well established. But our system is neither the dominant mode of sex determination, nor a more “correct” version of it. A final lesson comes in with the fairly new discovery of polygenic sex determination (PSD), wherein multiple genes and chromosomes contribute to the ultimate sex of offspring. This can take the form of XY and ZW systems being combined into the same species, for instance. Domesticated cantaloupes (yes, the fruit) produce four sexes, and there is some evidence that several species of fish rely on PSD). This system is still poorly understood, but importantly, the added variation on each side of the equation indicates that even genetic sex is often not a binary trait. Perhaps it’s time to rethink our preconceptions about the divides between “male” and “female.”
Katherine Wu is a third-year graduate student in the Biological and Biomedical Sciences Program at Harvard University and is, as far as she knows, XX and not XY.
[1] … Making King Henry VIII’s decision to behead a bunch of his wives for failing to bear him sons a little misinformed. Oops. Not that he could have known at the time – no one did. So, moot point.
[2] If only Anne Boleyn had been a pigeon.
[3] For the most part, the genes on the X chromosome only need to be present in one copy, hence the favoring of “loss” of duplicates on the Y chromosome. In fact, in women, who have two X chromosomes, one X chromosome in each cell is packaged into a dormant state called a Barr body. This actually happens at random in each cell (that is, it’s not always the X from mom or the X from dad that’s turned off – it can be one or the other), resulting in “mosaicism.” This is actually how the coats of calico cats are patterned, and why the vast majority of calicos are female! Cool fact: if you stumble upon a male calico cat, it is almost certainly XXY.
Further reading
- To learn more about why honeybees can’t produce males from fertilized eggs, check out this brief article: http://mbe.oxfordjournals.org/content/early/2013/12/06/molbev.mst232.full
- An excellent review on the evolution of sex determination: http://journals.plos.org/plosbiology/article?id=10.1371/journal.pbio.1001899
Featured image from Wikimedia Commons.
I really love what I reading
Please sorry dont worry m
I decided to read the article because I was looking for any updates to this human condition, the how’s and why’s of Science, you know, Facts. I know it is far more than a “choice”made because I listen. While I enjoyed the article and learned some new things, it didn’t really address what I was hoping to learn.
I have much love for humans and I still have faith in us to grow thru enlightenment. I read the comments because ya can glean helpful info in comments ya may miss otherwise. I tripped and fell though, I read and responded to an inane comment that forced me to say something because of his remark equating the equality of such claims be extended reciprocated as being valid. Sent me on a tangent I don’t apologize for because I meant it, But that wasn’t what brought me here, science and further info did that. And I returned this next morning because your reply so moved me.
Bravo, well said, thank you for so eloquently saying every word of it.If he isn’t enlightened, it wasn’t for your response! Can’t take some people nowhere. Lol
I can’t bring myself to scroll on by these disgustingly sexist, offensive and closed minded opinions.
Gender is a combination of social and biological factors which are very complex. Chromosomes as you suggested are not the sole deciding factor of how sex is expressed. Neither is society. Trying to place people in a strict binary gender is just not realistic.
It has been widely accepted by the scientific community sex expression is bimodal and expresses itself on a spectrum. Sex and gender are more like dials not switches. Biologically there are five components that lead to sexual expression by birth: chromosomal, genetic, gonadal, internal genital, and external genitals. Then there is pubertal (hormones) and psychological factors which come into play later on in development. Each component can be expressed individually or together normally or atypically in vast and unique combinations.
To say an intersex individual are rare or calling it a disorder does not negate the existence of this atypical expression of the two typical expressions. It is regularly referenced as a 3rd expression in scientific communities.
Using an example of atypical fingers and toes makes zero sense to me. It’s not even a very clear analogy. It’s like comparing apples and oranges.
We don’t categorize people by thier fingers and toes. We also don’t introduce people with atypical fingers and toes as defective. e.g. “This is my friend Groerge, they are defective with 9 fingers.” Or “This is my friend Anita, they removed thier finger with a saw and is now defective, should have used a SawStop.” Nor should we as it lacks empathy.
In all reality it wouldn’t be our place to call this out in the first place; it’s the individual who should decide how to address this if at all. We could notice a missing digit and politely ask if they could tell us about it. However, even asking is a little rude. Gender is really no different in that respect.
We do categorize people by gender and it has caused psychological and physical harm to “ram”, as you say, this point socially. As a society we should have empathy and accept people who are more comfortable using non-binary terms if they do not fit in with the typical male and female gender expressions. We should also be respectful to people who wish to identify separate from their gender assigned at birth.
I’m not really sure how transgender individuals are proof of anything except it is up to them to decide how they are comfortable expressing themselves.
Transgender individuals are not mentally ill. “Being a transgender person is not a mental illness. But a transgender person may experience an emotional condition known as gender dysphoria. This can happen if the discomfort with one’s physical self is very distressing. It is most commonly experienced prior to a person transitioning. And it can cause dysfunction in their day-to-day activities like work or social events.” Deb Thorp, MD
If anything the struggle of mental illness in the transgender community has more to do with societies poor treatment and lack of empathy in my opinion. If our society didn’t put so much pressure into conforming to unrealistic binary gender roles perhaps some of the mental health issues would lessen.
Science does not prove homosexuality is unnatural. Homosexuality is common in over 1500 species. Homophobia is unnatural and only found in the human species. Furthermore, a “study published Tuesday in The Journal of Sexual Medicine suggests that it may be homophobia — not homosexuality itself — that has elements of a psychiatric disorder.”, Rebecca Harrington author for Business Insider.
There is absolutely no evidence to prove “If you are a single mother and have your son grow up only around women he will more likely to be a homosexual than ever.” In fact phycologist Peggy Drexler’s research on the subject concludes “boys who are raised in single-mother homes are just as likely to develop into happy, healthy adults as boys raised in households with both a mother and a father.”
Your sexist rant “A society starts to fall when the gender roles are being mixed or breaking down. There’s a reason why men are more physically mentally and emotionally stronger than women.” and “women don’t make good leaders they are emotionally weak.” and more is highly offensive and again incorrect. If anything “harmful gender norms such as this deny millions of girls their rights to education, health and independence”, ~savethechildren.org
I would say lopsided sexism such as yours has contributed more to an unhealthy society than neutral or swapped gender roles.
Your constant assumptions and projections are exhausting and out of date but despite this I must keep going because this ignorant, abusive and hateful rhetoric cannot be left unchallenged.
More women are not single and unhappy now. Once again I will site a research article indicating single woman without children are actually happier, ~psychologytoday.com
You go on to make a ton more disgusting assumptions about woman being useless, sexual objects and some more dated dribble about aesthetics of women. It’s not valid to the point in anyway, highly offensive and really makes me question your mental health status and childhood upbringing.
I sincerely believe society is and will continue to move past your outdated, sexist, harmful, narrow views and become more accepting, empathetic and equitable for all.
Your view of humanity is revealing and alarming at best. I cannot express enough of my disgust regarding your rant. I really hope you do not have children.
Enjoyed the article! Not so much on the unsolicited anti-trans comments.
I agree with you
Various topics will be kept in this comment. Gender is not a social construct gender is binary. In nature reproduction is the rule you humans reproduce sexually meaning it takes one man and one woman to reproduce XX and XY. There are two genders and only two genders XX female XY male respectively. There are multiple other birth defects that are brought up in discussions like this claiming and supporting there are three or more genders or sexes. In school we are taught we have 10 fingers and 10 toes. There are people who have 11 toes or 9 fingers but we don’t say they are normal. Trying to ram intersex or a birth defect into a tradition is absurd. Existing proof is trans gendered people they could either believe they are a man or a woman. It’s either or my friends there’s no in between. Trans gendered people come to speak of it are mentally ill. They persistently consistently believe they are something they aren’t. No one is born in the wrong body. It’s all in their confused minds. They have the highest suicide rates and self harm. Actually the entire LGBT community has the highest suicide and self harm rates ever. These people need mental help. Science proves homosexuality is unnatural. If you place 100 homosexuals on an island and 50 straight men and 50 straight women on an island which generation will last longer. There won’t even be a generation for the homosexuals. It’s self explanatory guys and I don’t know why these people don’t get the help they need. You can’t really blame them. Humans are emotional creatures. They can easily be manipulated and deceived. People are influenced by others. If you are a single mother and have your son grow up only around women he will more likely to be a homosexual than ever. It is honestly sad to see the world like this. That is why the best way to raise a child is by loving parents one man and one woman that is how healthy women and men are formed. Childhood is everything it determines the type of man or woman you will be in the future. A messed up childhood can cause detrimental damages to society family or thyself. The absence father in a child’s life has been a problem in America more crime from the children or adults who’ve grown without a father figure. People are trying to confuse children now with LGBT when those people need severe mental help. A society starts to fall when the gender roles are being mixed or breaking down. There’s a reason why men are more physically mentally and emotionally stronger than women. Since the start of humanity man has taken care of his wife and children. The woman takes care of the house and children and has always had that femininity in them they are born loving and emotional. That is why we don’t have a female president yet because women don’t make good leaders they are emotionally weak. They beg for power and when you give it to them they don’t know what to do with it. This is why more women are single and unhappy now. They don’t need a man to provide at all they are independent through hard work or simply spreading legs on the Internet. Women make their own money now and don’t need men. This generation of women will be the worst. It comes to reason why women don’t want this protection men provide for them and his children. We will never know why women have a problem with a man providing for them and their children. Men have invented the essentials in life. The light bulb the wheel and have made weapons that can kill the earth. We’ve made species go extinct without trying. If women were a different species they would be dead. The only reason why women are valued is reproduction and sex. Men look at women as sex objects. This is why men love a skinny woman who is in shape and fit. It’s your human instinct to look for a mate to reproduce with. This is why men don’t like fat women. If a woman can’t take care of herself then what makes a man think she can take care of children. Women are born valued men have to work themselves up to be a man. Women look at men as success objects that’s why women love tall strong rich men. They want someone who can provide for them and a family. Now the narrative is shifting into the opposite and they complain why. This is my idea of humanity and if it doesn’t make sense I will gladly try my best to answer your questions.
hah of course your sexist. you cannot change your sexual orientation. your attracted to who your attracted to. you cant control it. the only thing you can control is how you act upon those feelings. by means of ignoring them or acting upon them. you seem to believe a womans only job is to take care of children and to be a personal incubator for men when in reality they are not. you need to open your eyes to the changing world around you and adapt to it. Also, having 2 fathers or 2 mothers or just 2 non-binary parent does not effect how they love and care for the child. Having a woman and a man have a child does not always mean that, that child wil grow up knowing what a healthy relationship will be. Newflash my parent were straight and gave me very wrong ideas on what a healthy relationship should be. i said it before and ill say it again. please open your eyes to the world and stop being such a sexist prick.
A sexist and stupid answer.
Obviously a humans worth shouldn’t be measured by how well they can reproduce. If you place 100 men on an island obviously no children will result. This doesn’t mean there is anything wrong with men of course. The LGBTQ+ community has these high rates of suicide and self harm just because of people like you. People don’t accept them, punish them, kick them out of their homes. They aren’t allowed to get married in many places, and aren’t accepted socially. Two women or two men in a relationship is shown as shameful, and having to hide this constantly from judgmental people (like yourself) is exactly why they have the most mental health issues.
An extremely sexist answer as well. Women do not look at men as success objects. I can say that confidently as a woman, along with all my female friends. “Women love tall strong rich men.” This made me laugh. You mean attractive men? Of course! Why wouldn’t women like attractive men the exact same way men like attractive women? It’s human nature. The reason men invented all these things (wheel, lightbulb, whatever) is because women were locked up in the home to take care of children. Being a housewife was the only profession available to them, and the world was extremely misogynistic. Female inventions had credit stolen by men. Really, women were treated horribly back then. Now women invent brilliant things just the same as men. Albeit, because of sexism, we still haven’t caught up just yet.
Yes, being gay or lesbian or transgender may fit into the category of mental illness. But then, so should not liking certain foods, being colorblind, and being left-handed. There is nothing wrong with any of these things. Being homosexual is not something that can be changed. You seem to think people can “turn” homosexual. That is not true, you are simply born that way. The same way you know you are straight, you will know you are gay, bisexual, lesbian, etc.
If you have any problems with this reply ask and I will answer.
“Yes, being gay or lesbian or transgender may fit into the category of mental illness. But then, so should not liking certain foods, being colorblind, and being left-handed.”
Strange comparison.
Being gay or lesbian or transgender has no relevant comparison to dominant hand, color blindness, or taste preference. A person’s dominant hand does not preclude reproduction, nor does it significantly lessen the individual’s survivability. Taste preference is simply a preference, arguably based on taste bud development and placement..along with other experience-based stimuli. Colorblindness is caused by deformation of the cones in the eye.
None of the three things you brought up for comparison are indicative of a mental illness. They are physical traits.
A more apt comparison would be to pedophilia, which is a mental illness and has no cure. It is the most apt comparison because it deals with an individual’s sexual urges and preferences, and is not a choice. Nor is it a mental illness we have a cure for. Would you argue that an adult having sexual feelings towards a child is something we should accept because they were born that way and have no choice regarding how they feel? Or would you advocate for them to receive whatever medical care and therapy is available so as to come to terms with the affliction and thereby do their best to integrate into society?
Ok, boomer.🙄 You sound like a very religious person who has been under a rock for 30 years .
At 5, realizing the clothes, types of toys, underwear I would have to endure through this new journey I found myself in, was going to be lifelong, no changing it. I was going to be a girl, always, and that sucked. When my mom cut my hair (dad said it was always messy, so cut it) I was ecstatic! People in stores thought i was a boy and i didn’t correct them. Going into new schools, kids would tell me later, they thought i was a boy by “the way I walked”. I rode a minibike before a bicycle at 6. Easter was torture being forced to wear a scratchy dress. I was always jealous of the boys getting the better toys, having short hair, and having muscles without really trying. This isn’t about sexual attraction as all of this was going on before high school! With that said, I had little crushes on my pretty teachers, older sister’s friends, then Jodie Foster, Madonna, etc. Dad taught me the world is narrow-minded, so go ahead and wear baseball hats, no makeup, and boots all your life, that’s your prerogative, but don’t be surprised if you lose opportunity. Harsh? Maybe, but this one journey around the earth was the best, once I made the best of it.
I would never want to oppress myself by taking extra hormones and shots, cutting off body parts, or adding them. Who knows how this will affect your body, bones, nerves, endocrine system, immune system, neurons, brain later?
Many people aren’t their ideal self, have disabilities, or dealt a hand of bad health. There’s blindness, MS, Cushings Syndrome, Diabetes, dwarfism or hundredsof other permanent anomolies. They had to make the best of it, and had to work around the society of the time, why shouldn’t I? Hollywood stars with lots of money,
no contentment may want to spend their way into happiness thinking they can jusr become the sex they felt like. But to me, this is a terrible role model for our young society. They have the money to fix it if they get it wrong, or it doesn’t make them happy, where many young people, especially lower income, cannot. Do we really know how many transgender people really become happy after radically altering their body, and hormones? We need to grow as a society by ACCEPTING one another, in the part of the spectrum we were born at. Men in dresses and makeup, with a penis, could be normal. Women in baseball caps, or 3-piece suit is normal and ok.
Then we can truly teach our youth about acceptance and loving themselves.
I KNOW my brain has always been different than my body, and I don’t know why, but maybe this is evidence of 2 more genders, a brain/body opposite and if society would understand this, people wouldn’t feel they had to change their outside to match as we would all be “normal”.
It’s the body God gave me and, thankfully, my dad told me how the world was going to be in my one and only little girl journey on this Earth.
Terry56, your father and mother were wise and it seems like you are aware of it.
I am an XX chromosome female, a woman. When I was a little girl, I liked blue colored everything, I hated dresses, and I preferred playing with boys. My mother cut my hair very short because it was so thick and curly, usually full of knots. I was often mistaken for a boy. As an adolescent, I hated itchy pantyhose, pumps with heels, and wearing cosmetics. I liked science and math, and studied engineering. I liked boys, very much! I still like science, math, engineering, and being in the company of men.
My mother is beautiful and feminine. I am not. Until about age 12, my father taught me everything that he would teach a son, but also insisted that I be my mother’s helper, as a good daughter should be. My mother and grandmother needed me to help with cooking, laundry, and growing food. My father told me, many times, that I shouldn’t be dependent on a man’s goodwill for my livelihood, but that it was important to listen to my mother about how to be a good hostess. (I didn’t grow up to be much of a hostess but have mastered the basics lol).
If I were an adolescent now, I might believe that I am transgender, and thus pursue FTM “gender transition”. That would have been a terrible mistake! My adolescent self would have probably enjoyed the drama and excitement of being different, of needing treatment for an exotic medical condition. I was grumpy, depressed, anxious, full of self-doubt from age 12 through 20. My adult self is grateful for being normal and healthy, the way I was born. Just as you said,
… and He was right.
Fascinating article and the comments have been equally enlightening. I’ve long felt I understood why sexual reproduction evolved, but now I better understand it’s also really an umbrella term for a host of different variations that nature has explored.
Sexual dimorphism is a reality that helped the human species to survive a dangerous world. Otherwise we wouldn’t be here or would be a different kind of organism. Most human beings now live in less brutal times, with a long life span and minimal existential threat. The full possibility of gender identity, once unexpressed in the struggle to survive, emerges. We understand more about all the variations on the human theme that are possible, even if such a variation occurs in less than one percent of the population. We can acknowledge that nature ‘s strategy is to make XX and XY people, but the creation process isn’t perfect, and then 9 long months of fetal development adds more variables. So the question for society is, now that life is about more than survival and we have become more aware of variations on the human theme, how do we define human rights for everyone. Along with this, how do we construct conditions for a good outcome of future civilization and avoid stagnation or self-destruction. How to allow all people to be the best, happiest, most self-fulfilled versions of themselves, while making sure society also functions well and is productive and advancing.
Statistically, it does certainly appear nature is trying to make people into two sexes. But as human society advances, it also has to acknowledge the complexity and fuzziness that surrounds this rule. As trillions of tiny building blocks of life self-assemble, it doesn’t always go according to plan. The ramifications of acknowledging this “fuzziness” are many, and demand us to think and perhaps be ready to challenge our own assumptions of who to accept in our human tribe. In the wisdom of acknowledging the complexity of life, we can acknowledge gender dysphoria or gender fluidity as possible outcomes of human development, even if statistically somewhat rare outcomes. This acceptance shows scientific understanding and, moreover, compassion borne of a more inclusive understanding of our human family. However in this fuzzy, but generally more inclusive arena, the challenge is where to deploy new objective definitions of gender status so laws and protections can be written for the greatest good. In our wider accommodations of gender, I personally don’t believe we should descend into total relativism regarding gender identity, decoupling it completely from biology. I think this would be exploitable and potentially destabilizing to the ideal goal of a high-functioning society. At one extreme, society can no longer humanely ignore the full spectrum of gender outcomes, but at the other can’t function by granting rights to all possible self-proscribed identity realities. Thus, for example, allowing XY trans-females competing with XX females is a rightly debatable decision. It speaks directly to the hard realities confronted in that gray area. “It’s not fair to true women.” “Well wait a minute, what is the definition of a woman?” Perhaps as gender re-assignment technology improves in the future, we will be able to minimize the XY/XX phenotype difference to a degree where much of that particular debate is not an issue. Of course, once we are in that brave new world, new debates about what it means to be human will make the gender argument seem quaint.
For now the effort continues to define a world with the most good for the most people, given the knowledge of the time. Hopefully, with a more widespread and nuanced understanding of the complexity inherent in human evolution and development, it will lead toward more inclusiveness of variation on the human theme.
McGill University. “DNA Not The Same In Every Cell Of Body: Major Genetic Differences Between Blood And Tissue Cells Revealed.” ScienceDaily. ScienceDaily, 16 July 2009. <www.sciencedaily.com/releas
People are forgetting how genes play in developing genitals, not just chromosomes. The one and off switch…
This along brings a lot of possibilities in how hormones can change things