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?


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.

Figure 1: Five (of many) sex determination systems. A. XY system In humans, females are XX and males are XY. B. ZW system In birds, females are ZW and males are ZZ. C. XO system In insects, females have two sex chromosomes, but males have only one sex chromosome (while retaining two copies of all non-sex chromosomes). D. Haplodiploidy In honeybees, females again have two sex chromosomes while males have one, but in this case, males have only one copy of every chromosome. E. Thermal regulation In some reptiles, the temperature of the surrounding environment determines the sex of the offspring.
Figure 1: Five (of many) sex determination systems. A. XY system In humans, females are XX and males are XY. B. ZW system In birds, females are ZW and males are ZZ. C. XO system In insects, females have two sex chromosomes, but males have only one sex chromosome (while retaining two copies of all non-sex chromosomes). D. Haplodiploidy In honeybees, females again have two sex chromosomes while males have one, but in this case, males have only one copy of every chromosome. E. Thermal regulation In some reptiles, the temperature of the surrounding environment 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.

Figure 2: Sex determination in honeybees. A. Honeybee haplodiploidy Fertilized eggs inherit a set of chromosomes from their mother and a set of chromosomes from their father, and are always female. Unfertilized eggs receive half their mother’s chromosomes and are always male; males have no fathers. B. Sisters before mothers Each daughter receives all her father’s chromosomes and half her mother’s chromosomes. Thus, sisters are more related to one another (75%) than they each are to their mothers (50%).
Figure 2: Sex determination in honeybees. A. Honeybee haplodiploidy Fertilized eggs inherit a set of chromosomes from their mother and a set of chromosomes from their father, and are always female. Unfertilized eggs receive half their mother’s chromosomes and are always male; males have no fathers. B. Sisters before mothers Each daughter receives all her father’s chromosomes and half her mother’s chromosomes. Thus, sisters are more related to one another (75%) than they each are to their mothers (50%).

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

  1. To learn more about why honeybees can’t produce males from fertilized eggs, check out this brief article:
  2. An excellent review on the evolution of sex determination:

Featured image from Wikimedia Commons.

112 thoughts on ““I’m XY and I Know It”: Sex Determination Systems 101

      1. As adults we have the freedom to exploit ourselves if we are adults but pushing this junk science in children is a form of pedophelia in my position of peon ship to the deep state that is pushing this crap for profit Hey Politicians Leave them kids alone. How can such highly educated people be so ignorant of any common sense? Highly educated people in America could be our downfall try seem to be hypnotized by fakers of truth THE DEEP STATE, Inustrial military complex , or shadow government. People wake up and be free thinkers the left is a total lot and a portion of the far right are the same they feed off lost sheepWSKE UP AND BE STALLIONS FOR JUSTICE

        1. how do you know this to be true? and what do you mean by pedophilia exactly? can you define it, I have found in society people dont tend to use the actual definition of it nor understand where it comes from (there is over thirty years of research and meta reviews and systemic meta reviews on pedophilia showing how it arises, even a few suggestions on how to prevent it over long term or lessen its impact, are you interested in understanding that research?

        2. WH What does your comment have to do with transgender? It’s difficult ro explore these topics when there is so much emotion attached, as in your comment. Bottom line, we do not know what causes transgender from a scienific viewpoint. But it appears that a genetic mutation might be involved. Transgender surgery does not happen to anyone under the age of 18. Most transgender teens knew before the age of two! And it has nothing to do with sexual activity.

          1. X doesn’t become y or s or anything else in Homo sapiens. It is what it is. If y isn’t there it can’t come from z or w. We are only capable of producing other humans unless someone really has created sheeple!

    1. Male and female He created them:

      Chromosomes determine if you are male
      or female, not your state of mind. Not surgery, and not hormones.

      Simple scientific fact.

      1. Bro did you read the article at all?

        “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.”

          1. So your saying there could be variations other than the usual XX and XY combinations?

            Interesting how you simultaneously reject and confirm non binary gender expression.

          2. Ah, “malfunction” is probably correct in that we individuals who don’t match our chromosomal designation (for instance, I am a 46 XY FEmale) end up this way due to genetic mutations. But honestly— it hurts to be described as someone with a “malfunction” or “disorder” or even “different.”…cuz this is just how we ended up. We live and love and learn and contribute and age like everyone else. How about trying to think of us as just not chromsomally like you happen to be?

          3. You are correct. The scientific explanation does not describe the mental and emotional side of gender identity. From my exploration, I have come to believe that a transgender child is that way from birth. (Watch “I am Jazz” if you disagree. They have video of her at age 2 and up )
            That’s the part of transgender that we do not understand, and research does not explain. However, when does this manifest? If a child is transgender child knows something is different, might not understand, but they don’t always have the words. When it is like this, the child might think they are gay. I have personal experience of this. My sister assumed she was gay and she lived that way for years before revealing she was trans. I believe there is the physical aspect, but that does not explain the mental and emotional side.

          1. Awh shit you’re right. Guess we can just throw out the concept of Down Syndrome since there aren’t that many. If there are few they don’t exist of course

        1. I read the article and it throws out the same tired platitudes to try and make their research support their predetermined opinions. Trying to confuse the issues regarding human sex determination by flooding the article with her opinions about birds, fish, insects, etc. I do agree that the odd mammal platypus is a missing link in mammalian evolution. Evolution moves over millions of years. Except for the rare mutation or abnormal development, the current human species determine sex , gender or whatever you prefer to call the two normal outcomes of human reproduction is based on the xx-xy system. A male cannot decide her wants to be a female and that is it. No mutilation and hormones can make him a female nor cannot he bare a child. Until recently, a man who thought he was a woman, wore women’s clothing, wigs, etc., was a transvestite. That’s the only trans anything I can remember.

          1. Funny. She presented hard science showing many species have additional chromosomes that help their sexual development. She cites studies You’re just to lazy to research them, but you can’t wait to insert your opinion, which is only an opinion.

      2. Ha here we go. So you believe in an imaginary sky daddy but you reject the idea that people don’t all fit in a simple binary model and that science is starting to underhand that its3.ore complexe than that.

        Besides your religious fundamentalist ideas and bigotry. What other reason have you got to reject these ideas?

        None apparently

      3. I am an XY female. CHROMOSOMES alone do not determine if you are male or female. Genetic mutations have far more to do with sexual determination than whether one is a “pure” XX female or a “pure” XY male or a “hybrid” XY female or XX male or an XXY or XYY or even a mosaic. Wake up world! Humans are not chromosomally nor genetically binary!

        1. If you have a Y chromosome your genetically male. I’m familiar with your condition where due to genetic abnormalities you do not develop as a typical male the testicles do not descend they stay in the abdomen, external genitalia appear to be female. Yet you do not have ovaries, and you do not menstruate. Socially you are a woman. you were raised as a girl. You look like a girl. But on a genetic level you are male.

        2. Lol did you not read the paper? Literally says that xy can develop as female but that it has to do with an issue in sry but that you have female traits, ie breasts, labia, vagina, not that you feel like you are a woman, it has everything to do with the physical features present not what you think should be present, hermaphrodites are a real human genetic disorder, its 1 in 1 billion or trillion that have this abnormality, so this whole trans gender thing is not trans sex, its just what you identify as and not what you actual are biologically sorry not sorry, science has concluded on this

          1. It’s actually cited to be somewhere between 1%-2% of the population born intersex. It’s about the same as people born red-headed, so it’s not as rare as people think. Unfortunately, up until very recently, doctors would mutilate babies and choose the sex assignment at birth without consulting parents/guardians/family/the individual, which often caused serious issues as the child matured.

          2. “1 in a billion or trillion”. There are just over 7 billion people. Good statistics there, smooth-brian.

          3. Who is arguing that transgender = trans sex. Im a trans woman and i certainly am not. I am genetically male, but for some reason my inherent identity the image my brain has for who i am is in difference to my body. It is not a choice, or a want, it is a inherent sense of oneself being different. We know it exists, we know it is not a mental health disorder, now we need to discover why it exists, following on from this article, one hypothesis could be that it is related to genetics and biology.

        3. Here an old cliché suggests itself: an exception that proves the rule. An exception certainly does not prove that the rule doesn’t exist!

          I do feel there’s a middle ground here that gets lost. In a sexually reproducing species like ours with a well understood genetic underpinning the female/male binary is the default. But being the default shouldn’t mean that individuals that don’t fit the binary are not “normal” or are necessarily some kind of mistake. They’re just variations within a larger norm.

          Unfortunately in the present discourse both sides want to reject this complex reality and simplify by de-normalizing the other, whether its the anti-trans folk on one side wanting to exclude the non-binary, or on the other side those that would reject the basic reality of the binary default. We need to walk and chew gum at the same time, to cite another cliché. Accept the binary default while fully accepting and granting full rights to the exceptions.

      4. Did you even read the article? Honestly, how are people this ignorant. It’s all science, not one single opinion in this article. Yet you ignore everything and race to the comments with the knowledge from your bible study group.

      5. Can you find me an answer? I’m an xy chromosome woman who developed normally with uterus, ovaries and testicles; completely fertile and made myself pregnant 4 times; all healthy normal births xy chromosome.

        1. I’m just curious, if you impregnated yourself with your own semen, that would not only be a miracle but in every scientific/medical journal ever. so why is this not something that can be found anywhere, and yes your story would be published without your consent, they can to that they just have to follow HIPAA guidelines

    2. agreed, it seem to me that they are just pandering to the last brain cell to appease these people

  1. On strictly medical terms. there are 3 things that are possible, the baby has vagina or a penis. or in VERY RARE cases has a different condition that due to how nature decides to shape the human body, can end differently, usually denoted as a defect. modern practices have become better at solving this issue however.
    As a surgeon, i apologize if i seem slightly absorbed, but i have to take a firm stance on this topic. currently the two most logical medical solutions to gender are:
    1. you are what you are born with, body modifications are to be treated as nothing more than cosmetic. I can somewhat agree as whether you have a penis or vagina at this current time, you still carry either XY or XX in your genes and your size/muscle growth will reflect it.
    2. you are what you are equipped with at the current time. this is rather simple. if you have a penis, you don’t go in the women’s restrooms and vice-versa. this stemmed from what seemed to be a rise in alleged cross-sex rape cases from both sexes, in public restrooms. I see the point here, if you have a little girl. you don’t want her to have an encounter with a man in the women’s restrooms.
    Both seem pretty understandable.
    but the one thing that i cannot accept is the talk of non-binary gender spectrum things.
    gender isn’t a spectrum. you have male and female. subcategories of this are male and female. if your trans, then you are still either male or female. you are not nonbinary gender fluid whatever. i’m not saying your less human, but i am saying that you are not as to who you claim to be. i guess at this point we have to go as far as to say it like this:
    look at your hand right now. it is made of cells. those cells came from DNA. which is either XY or XX. nothing more, nothing less. both sexes have their far share of problems the other cannot fully understand, neither has it easy. but moving away from your self in order to feel like your self IS IN FACT a very bad mental state to be in. sure, it works for a moment. you get lost in the illusion and feel more free. but take a moment to put the illusion aside and reflect on your life choices and their consequences.
    physicality and medicality should always be put over opinions and politics. so its like a direct slap in the face that large, reputable universities, whose job it is to provide students with this valuable knowledge have turned. they are abandoning everything they once were for nothing.
    more people know what gender studies are than the are people who know what STEM even means. that should be a pretty large indicator right there.
    the fact that this is even a thing to discuss sickens me. we could have spent this time gaining a deeper understanding of cancer, or figuring out how to purify nuclear waste, build an animal shelter, go donate blood, go plant something. imagine all the time and money this new culture has demanded that could have went to better more productive things that have a practical purpose.

    1. Looking at the first and third comentors it would appear they are experiencing the back fire effect.
      1)Our first commentator jumps to calling this junk science. Not really helpful or insightful. The point was to get people thinking about gender and how we as humans perceive it.

      2)Our third commentator speaks of medical terms, but deviates from medical to personal matters and then includes scare tactics i.e. rape. Please don’t ignore that a disturbed individual will do horrible things regardless of what sign is on a bathroom door. It was also not mentioned that same sex rape happens.

      Both the article and the surgeon miss 2 conditions that make the gender based on DNA not so simple.
      A) Intersex, a condition where a person does not fit into a nice neat column A or B of gender/sex organs. So XX is a girl and XY is a boy. Neat, easy, no thought. Just look at you hand, well what if your hand’s DNA reads XXY or XYY. Not so neat and simple right. Is check their pants they say. Ah that can be a problem too. Many who have XXY do not hconditionnizable genitals. So what to do?
      B) the second condition chimerism is when one person hold DNA of more than one more individual. So that hand may not be XX like the rest of you. Google thus one if you’ve never heard of it. The part that makes this interesting is there was no way of telling if you have this without testing multiple parts of the body’s DNA. So yes, it is possible you’re brain (or at least the part of it) could be XY and the rest if you is XX. The thing is medical science can only guess at how many people have this particular condition since it requires multiple DNA tests and I don’t see many people signing up invasive surgery to have their brain tested just because they feel different.

      The real reason this is all being discussed is that gender matters to society. If male amd female were true equals then it would not matter if you were male, female, or inbetween. We have constructed roles and expectations based upon our (perceived) gender. It’s not about whether you are male or females; it’s the notion of conforming to assigned roles. It’s not about genitalia. It’s not about not about restrooms any more than it was about fountains or where you could sit in a bus. It IS about human beings. If you have never been discriminated against because of the way you look or act you will never unstand what it is like. I don’t want people to see my skin tone or hair and expect me to be something just because of my genetics. Treating people a certain way just because of their genetics is not a good idea, just ask a Jew.
      Unfortunately for us all what it comes down to is that humans see a thing that is different and don’t understand. What is not understood is feared; what is feared becomes hated. Thus what we hate we destroy.

      1. I could not stop laughing while reading your reply Lauren. As the facts stand this is all there is XX and XY. Everything else is physical or mentally retardation, or people in serious need of professional counselling. Which is less than .001 of 1% of the world population, without even needing to look it up to do the research. Which sums everything both of you have said. Nice and tidy. Truth is if gender was fluid, then so is race, which then means both are only a state of mind. Which in that case I identify as a polka dotted apache helicopter, and you should respect that. Then I should also be able to say I identify as a woman to be able to apply for and get a small business administration loan for Women-owned businesses, from the government which is specifically an advantage only for women. From the Funny part is that will never happen because people only want equal rights as long as it is in their favor. Fun world we live in. I probably wouldn’t have gone that far, but you brought in religion in your reply and lost credibility.

        1. You just said all non-binary individuals have mental retardation. Cute. I hope you share your opinion with everyone you can.

        2. Race is genetically non-existent though. Two identical-looking penguins might have more genetic variation between them than a black and white persons. Even “physical features” that distinguish specific “races” overlap across many “races.” In reality, people develop according to their ancestry’s geography, and these are merely small adjustments to survive in different climates (go closer to the equator for many generations and your family tree will develop a darker skin even if you somehow “maintained racial purity”) and conditions. Comparing race to gender is a waste of time from a scientific standpoint. Just tossing my two cents to the conversation.

        3. But, do you actually WANT to identify as a polka dot helicopter? I’m guessing not.
          Previously women weren’t allowed to go into certain places, or have a vote. People in this forum back then would have made awefull comments and thought these things abhorrent to change.
          But change them society did, and all based on gender politics.
          Things change, that is human nature.
          The naysayers just need to get on with their own lives without interfering in others, no-one is attacking them or telling them they are wrong, even though there may be ways in which they themselves are morally or legally repugnant.

        4. you do realize that the percentage of gingers with blue eyes is also like 1% right? so are all of them f-ed up?

        5. Unfortunately, Jake, you are wrong in this case. And I am scientific proof thereof. I am one of those that don’t fit neatly into the XX or XY category. I am – to classify myself according to your binary system – a classical male in appearance. Although even there I already display differences from the strict biological binary system: eg. while having a penis and what appears to be testes I also have had – my entire life and I assure you not by choice – breast development that would be more considered female. And the penis and testes in my case are devoid of their normal function. Testes have never been fully developed. My body does not produce any sperm cell and when comparing the testes to that of a normal male they are formed at a fraction of the normal size. Contrary to that underdevelopment sits a hormonal function in my body that is far beyond the normal boundaries. My FSH production is a whopping 40 times higher than that of a normal human. My testosterone levels are nearly non existent making the estradiol the dominant function of the two, which you typically associate with female characteristics. However, contrary to normal scientific understanding – where the link between testosterone levels determines the outward visible hairgrowth for example is the polar opposite of what you would find. Given my extremely low testosterone I should be displaying minimal hairgrowth, yet my reality was the opposite: head to toe covered in hair. None of this leads me to say that I believe gender is fluid. But I will say this: If you’re confronted with a body the likes of mine, I am sorry but it does mess with your head. The totality of all the things that are biologically divergent in my case have led to differences that really are not fun to experience. My life has always felt like a rollercoaster never knowing which way to go. Intercourse experienced from the male point of view has for me always been an experience that ends in pain. (at the moment of orgasm I literally am in pain, because of the malfunctioning in the testes) . And it really does mess with your head if you look in the mirror and have a body that doesn’t add up. As I mentioned, the breast development has for me always been a point of embarrassement because no matter how rigorously I exercised or watched my diet, they were always there. Socially, I was raised as a man because of how the appearance of a penis and testes. But it wasn’t until late in life when fertility tests came back with inexplicable results that the full image of my biological layout was formed. I can assure you, three fertility experts, one of which being Prof. Ombelet who is an world leading authority in fertility confirmed that they had never seen results like mine. Currently, and this is after long discussions with medical staff, I am undergoing hormone treatment whereby I am now being administered female hormones which create a more clear dominance of estradiol in my body. It has had a positive effect for me. It feels less messed up than I did before because my is also more clearly developing towards what you’d classify as female characteristics. That choice was not made because of some fetish pike dream. It was a choice based on the experience of the male characteristics that led to discomfort. One thing I can admit that is being achieved is that the physical discomfort I used to experience as male has decreased which obviously has had a positive effect on how I feel. I cannot even begin to describe the relief I have felt at being more in harmony with my own body. I am quite pleased with how medical staff as well are dealing with the situation. And perhaps that is a point that is still missing in this article: We are an evolving species. In evolution there is always divergence. It is in fact necessary in order to evolve. The science, even though far better than even a few decades ago, has not reached the point where we fully understand how the human body functions at most detailed level. If only society could learn to accept that even in an apparent binary system, you will still have exceptions when something doesn’t develop as you would expect. It’s like conjugating a verb in language….there are rules to adhere to but there are always exceptions that don’t neatly follow the rule. It doesn’t mean that the verb is malfunctioning and can’t be used. It just means it’s different.

          1. The fact that you have hormonal abnormalities does not mean that you’re not a man.

          2. Erwin, I am glad you are getting the medical care you deserve to allow you a to enjoy the human experience without pain and to feel comfortable. In my thoughts, you are precious and celebrated as you share uniqueness that in fact are minimal considering the similarities shared by all humans. Your uniqueness, particularly chemical advances understanding that broadens scientific inquiry and understanding of what is capable within the oue human species. In this, you are akin to with the most brilliant and artistic people who ever lived, as their DNA must have in some capacity been a combination that is not in accordance with “normal.”. With resolution of your pain with sex and comfort in your form, you remain a spectacular human and I admire your ability to survive and thrive beyond what was thought possible. You are a blessing, and I wish you wellness, confidence, joy, faith, fun, love, and goodness always. Thank you.

          3. I hope I can reply to you without offending you, especially since you didn’t ask for a reply. You are obviously very unique and I hope you can become comfortable with your body by what ever means possible. I am a conservative white male 65 years old and I am confused with gender fluidity. I feel the majority of people going through such issues are doing so out of an ideology by people that don’t even know what it is to truly be affected by the challenges you face. Record numbers of children are identifying as gender fluid and the have normal XX or XY chromosomes with normal genitalia. Why do you feel there has been such an increase in young kids wanting to change their gender. I don’t believe it is because society has become more tolerant so more people are coming out

        6. Jake, the fact is that there are people with XXY and XYY chromosomes and also chimeras that can have two sets of DNA in their bodies.

        7. People only want equal rights if it is in their favor? Frankly, it is difficult for me to comprehend why we can’t just do the right things from the get-go from the start cause we all know what the right things are as Equal Members of the Human race. I don’t have anything I can learn from a mind that believes that statement as truth. As a person who is not gay or whatever but I think therefore I am inclined to believe we have More to Learn about what is Factual in explaining why some folks are gay, and all the other letters used to denote, because I have two gay brothers and I’ve enjoyed the friendship of an assortment of friends with many differences, I happily embrace treating the differences as a positive instead of a negative. Sameness would be boring indeed. So, for me, believing in equal rights is the way to go buddy, just as letting outlooks, opinions, and ego define a person’s value as a human being- very shallow indeed. Science is ever evolving and it will one day become clear what determines or influences ones personal choice if Organized religion doesn’t continue to keep learning in a vacuum . But hey, these discussions are part of the evolution too. Science and spirituality are equal tools in the race to get out of the baby stages of human evolution. I’ll be happy when the facts of what and why are explained for what determines sexual preference because I tire of people I love being abused, misunderstood, and judged. Equal rights is not a burden, it’s the right choice of response… and women in my state were not even allowed to sit on a jury in 1970, so yeah, I’m all for equal rights. And hey, I drank from the fountain my whiteness was prevented from sipping from that they told us by sign and society, water tasted just the same. I been fighting for equal rights all my life because if all don’t have em, none are free… I probably wouldn’t have went this far but you brought equal rights into it.

      2. Lauren, humans have diseases, we all know a man is XY and a woman is XX, if we find a XYZT that is not standard or normal, it is an abnormality.
        Bottom line is that people do not change who they are just by thinking or feeling sth.
        I can wake up tomorrow felling I am a Bear, dressing as a bear, hibernating as a bear but this DOES NOT make me a bear, I respect the feeling and freedom of a bear-man to be who he wants to be, but it is a disease and I am not obligated to call him Mr. BEAR and pretend I am blind

        1. This, exactly. What’s more, we should help the individuals adapt to society, not society adapt to them. If you had a glove factory, would you adjust things to produce 4 or 6 finger gloves because a tiny percentage of the population either is missing a finger or has an extra one? Of course not. Certainly, you might take them into consideration, and prompts to you for doing so, but changing the entire program of your factory to adjust to that minority would lead you to bankruptcy because the vast majority of people have 5 fingers. Furthermore, I certainly don’t want my kid chopping off a finger because he feels like he has 4 fingers and having a 5th disturbs him. Now imagine that the 5th finger is, you guessed it, genitals. Then again, I also don’t want my kid to hang himself because we just won’t accept that he’s a 4-finger-having kid. The situation isn’t simple, so we must be very careful about how we go about things when it comes to these issues.

          Before anyone jumps on this (always happens), full transparency, the gloves and fingers comparison is for simplicity’s sake. It obviously isn’t a perfect parallel, so don’t go thinking I’m trying to demean or brush off what trans people go through.

          1. Hey Carlos,
            I think your idea that we should be helping individuals to adapt to society is a great starting point, but I think your perspective on gender dysphoria is, willfully or otherwise, disrespectful. Though you did say “it’s not a perfect parallel”, it’s still your main argument, so let’s dive into your finger analogy.
            I can see how it’s compelling to think of in this manner – it’s a very cut and dry, material argument, especially if you substitute the fifth finger for genitals – but I think that’s the exact point you’re missing.
            Sex and gender are two different things. Sex – biological sex – is what this article is about. It’s the layout of XY or XX chromosomes and how they determine the biological structures of your body. Gender is a set of societal expectations and – most importantly – self understanding. For many, this does stem from your biological sex, to some degree, but the science is set that “gender identity” is both real and exists on a spectrum. Studies show that personal gender identity is typically settled upon between 2-3 years of age, a year or two after the child recognizes a difference between genders, and does not usually change.
            To think that your son “feels like” a 4 fingered person, or “feels like” a bear is to equate a physiological fact of your son’s brain to a “feeling”, like one feels sad, lost, or frustrated. This is false equivalence. Gender dysphoria is not a trend, and not just a feeling. People do not go “trans” because it’s trendy, cool, or because everyone is doing it – that’s nonsense fearmongering.
            That would be like saying sociopaths simply don’t feel like having empathy, so they have turned it off. Or that someone with depression is just “feeling sad”, and really ought to quit it. It’s an outright denial of the concrete, material circumstance of the person’s mental experience.
            Let’s go along with the ludicrous metaphor and make it a little more equivalent, and hopefully we can come to a common understanding.
            Let’s say for the sake of argument that 4-fingered and 5-fingered people really are treated entirely different by society, that no one accidentally loses fingers, that the idea that the number of fingers you have is a part of anyone’s identity whatsoever, that there is a legitimately recognized psychological occurrence of people experiencing 4-finger dysphoria. Let’s also say that in the US, 1.5 million people feel the same way as your son – having been born with 5 fingers, but feel not at home in their own bodies because of the extra finger they have.
            Sure, your glove factory will most likely continue to produce 5 fingered gloves because, it is a factory, and making money is the most important thing. Systems that aim to make money tend to target the largest possible crowd – though a smart company (or startup that identified this niche in the market) might start selling 4 finger gloves at a smaller scale to capitalize on that factory as well.
            But who cares what a factory would do? Our government, and our personal lives, are not run like a factory would be. Our government should still pass laws stating that it’s illegal to discriminate against someone with 4 fingers, or 4 finger dysphoria. Our government should still pass laws saying that 4-fingered people are allowed to be in the millitary, despite perhaps having slightly worse gun-handling. Our government should still recognize, protect, and serve those members of our community, the same as you should, because you’re a human being – presumably with empathy.
            I feel like I should finish this by letting you know – the suicide rates of the trans community are largely attributed to the way they are treated. Hate crimes, discrimination, and the opinions of people like Ricardo, Jake, and Will – cisgendered folks who think that “the way things have been” is enough evidence to discredit the entire lived experience of hundreds of thousands of people they have never met.
            In short, I hope that if your kid – hypothetical or otherwise – truly does wind up questioning the difference between their gender identity and assigned sex, you don’t treat him the way this opinion implies you should. Being trans is not a disease, getting transitional surgery is not the same as cutting off a finger, and this sort of disregard from someone who isn’t directly affected by the subject is chilling to hear.
            I don’t mean to “jump” on you. You seem like a nice enough guy. I just want you to really think twice about your preconceptions about this topic. It doesn’t cost you anything to do.

        2. I don’t think you quite understand how people work.

          First off there is a gene typically found in Y chromosomes that stimulates the development of phenotypically (what is physically visible) male sex characteristics. However this is not always the case, so some people can have XX or XY and not be female or male, respectively.

          Additionally, it is not someone’s thoughts that determine a person’s identity, thoughts can be fleeting and elusive. A person’s identity is quite rooted in who they are, their consciousness/ego. Sadly, your example misrepresents the trans experience.

          However, the word “feeling” can have a variety of meanings depending on context. Typically, a trans person would use the word in reference to an “experience,” rather than a “fleeting emotion” as your context would suggest.

        3. Humans are not defined as only XX females or XY males. If there is XY females or xx males, then the xx female and XY males hypothesis was never correct and it has to be corrected legally, medically, socially. At this time, it seems it is best to categorize all people as homosapiens. Perhaps, as we advance in our knowledge or in development, it will change again. Simple XX female and XY male no longer represents out best knowledge of human life. Instead of fear and discrimination, it is best to embrace and celebrate what further knowledge this might bring and enhance our understanding.

        4. Yes, people can cope in poor ways. Mr. Bear man might have had a horrible childhood and needs to cope. Wanting to change your name and pronouns doesnt make you the gender you indenify as, but it helps you socially cope. Some people will use transgenderism as a coping skill not for gender/sex/genitalia discomfort but genral body discomfort. Alot of people can be harmed and will use transgenderism as a coping skill.
          Men with low Testosterone become depressed, they eat right exercise right, but still are depressed. Women with thydroid issues face the same issue. Hormones are readable in the human body on a subconscious level, its like dehydration. Your tounge isnt drying up and your lungs crackling when you finally think, “hey, i could use a drink.” You normally just drink water. This means humans are able to have a reading of self even when considered stablize. I will agree that it self and bun self are the mental disorders of transgenderism and not the sex determinartion syndrome effect it causes. Gender has for ever been a personalization of vibes. Girls soft boys rough. All vibes. Sex is whats in your pants. Sex can also be your chromosones. Sex isnt your hip shape (depending.). Men can have hippy hips, i think john mulaney made a skit about his hips. Sex can be seen in the bones, but that can also be influence by hormones. Can hormones really determine sex? Or are hormones a cause and effect of sex determinarion factors? People seem to be able to go on hrt with little backfire (depending on how they treat it, if its treated like candy, bye bye health, if its treated like a second puberty, then it should be fine, especially if the patient isnt taking bootleg hrt to double effects).
          Some people do have issues with hormones, wether taking medication like hrt or ssris (hormones generally not sex hormones only). Hormones are a reabale source. People can sense when their bodies arent matching up to a quota. Weather that quota be serotonin or estrogen.
          Remember, gender has always been a personalization, such as girl wear flowers and pink, boys wear blue and hats. Clothes are a personalization. Gender roles can even keep someone from running. They are very weird sometimes.
          Sometimes people become insecure about their gender and forgo ideas like painting or knitting, or the fem side of things, they may reject horse play or loud music.
          My point is, people yes can misuse the idea and make it emotional, while yes people are being emotionally impacted by not meeting a quota.

          Bunself is a disorder/coping skill. Its not science but phycology. Some people who are autistic or severly damaged as a child may use these terms to reject societal roles of fem and masc. Its human nature to cope with what is fear. Its a rare coping type and may only be seen as coping type used in those who reform back into a child like mindstate or those in depersonalization. (Someone mentioned here how moving away from yourself to get closer to yourself in using transgender idealogy.).
          Yes. Only 2 sexes.
          Non binary isnt a sex.
          But its there, imo in a gender context.
          Non binary is a gender standpoint of nutral and doing what you want, even if its against roles. I see alot of women who are nutral and come off as non binary, same with men who act more fem. They seem non binary.
          Gender is a personalization but its also a coping skill. Its a way to forge a new paths outside of ones self. The person we speak of may find their reflection of subconscious self a mess to clean. The emotional impact of trauma makes people act weird. Especially when done as a child. My other point is, transgenderism is real and biologically readable, but the idealogy of it (gender fluidly based upon the body and not mind) is a personalization of ideas.
          There is a fine line of biological and emotioanl in transgendered patients. Some benifit from the coping styles while others find they are moving away from orignally then metting the promised quota.
          Hormones are readable. The reason they are reable is just due to bssic cell communication. When my stomach has lets say…. old oil from popcorn in it. It will alert me and make me throw up. The old oil caused me food poisoning. I woke up in my sleep. This means that my body is awake and reading (hence why some wake up to a loud noise). This is disorder where subconscious distrupts consciousness. Like bipolarism or yada yada, they arent meeting a qutoa.
          There are certian systems that need to be in place, but if you talk like how your talking right now and ignore the fact of facts and dripple down into, no, and only no, and follow a linear pathway of this and no no not that then you lose the udea of science all together. Science isnt linear. You dont understand phycology well if you think mr.bear is just insane and only insane. Mr.bear was probably servely damaged as a child which is completely difference from traditional transgenderism of male and female (not bun or it self). Mr bear man wants to be in dreamland for a reason. Humans are not born broken unless (yknow.) But the genral populous isnt born with off (from linear set quotas of what is).

          You are still holding transgenderism as a mental disorder and it shows in your repersentation of mr.bear. as mr.bear doesnt have a bear quota in his body to meet while a transgendered person could have a qutoa of hormones to meet. You are really obscure with your hormone connections. Humans dont have bear hormones. That was redundent. Mr bear deserves to be seen as not mentally ill but damaged and transgendered people deserve to be seen as either coping wrong or not meeting a quota. Something your mr bear statement is hindering because we have to go through a whole process of redefining the ways people use transgendered idealogy again.

    2. So Will what if you were born with a vagina and have a XY chromosome?

      What if you were born with a penis and have a XX chromosome?

      Than what’s your gender?

        1. Not technical or scientific, I am a woman of 59, three children.
          I am xy, I have an introverted womb. Too much facial hair, normal puberty development etc. I do have family members of both sexes who identify as opposite, both male and female. So there is a lot more to it than than just xy…… I summise that other genes switch the sry gene on…. Mine are just broken

          1. Julie, no one has used the term “introverted womb” since 1914, in US appellate courts. There exists a condition referred to as retroverted womb, which is exclusively associated with fully XX chromosome females. It is not anything remarkable, it does not impede child birth, and it does not suggest that there are multiple genders!

            Homo sapiens is sexually dimorphic. We have XX females and XY males. There are sometimes chromosomal abnormalities. Surgeon Will describes this above. These are chromosomal defects, NOT evidence of anything other than sexual dimorphism.

            If you gave birth to three children, you are a woman. Period. End of story. Who told you that you are XY? They are wrong.

          2. Thank you for trying to help people to understand, I understand what you are saying. Sadly, most people absorb societal rhetoric typically spouted from unqualified individuals.

    3. Will, that you have a medical degree and are clearly against expanding your knowledge and learning continuation is terrifying.

        1. A surgeon that puts the bible over science and doesn’t even know the difference between your and you’re seems quite suspect. Does education for surgeons include remedial reading classes? Maybe it should have 100 years ago when he studied for it?

          1. Dr. Seuss – I thought the same. Also some help with grammar, re misuse of the word went, would be in order.

    4. ok will… i dont think ur a surgeon bc a real surgeon would completely understand how real the gender spectrum is. human bodies are incredibly complex and to limit ur understanding of gender to a black/white and inalterable LAW, is just embarrassing. humanity has been fighting back cancer and we already figured out how to purify nuclear waste. as a “surgeon” u should know that no scientific experiment ISNT worthwhile, because any knowledge gained is 100% better then ignorance. also, why do u care? should u, as a surgeon, want ur patient to be happy and mentally stable?? why take away options that could save someones life just because u dont like the cut of its gib u dummy.

    5. First, you are perpetuating a very SERIOUS misconception that trans people are molesting kids in bathrooms. Based on that, I’m guessing you’re from north Carolina & supported that garbage legislation. So now, I’m aware that you aren’t really looking into facts about the actual demographic of child molesters & just going off of your opinion. SCARY, considering you’re a doctor. Second, if you are actually a surgeon you would have had to go to medical school & tons of it. You of all people should know that genes are far more complex than what you see for sex organs. I also glean that you are probably religious, as you have completely bypassed hermaphrodites, you alluded to it but then called it a defect. The reason is because that would literally destroy your whole view on sexual orientation. As a medical professional, you should be ashamed of yourself for not being more open to the science you literally depend on daily. Shameful….

      1. Depends on how old the good dr is… my mother in law was an ER nurse in the late 1920’s and until the day she died she thought men had one less rib than women because of Adam… I wish I was kidding…

    6. Hey Will, sadly your a surgeon not a genealogist. It seems that you opinion contradicts the stance of hundreds if not thousands of more qualified individuals. Scientists that have actually performed peer-reviewed research on the subject.

    7. You’re a doctor? So then you would know that chromosomes can produce more than XY or XX. And that you are not simply born either male or female you can be born or hermaphrodite you can be born a female who with an XY chromosome and you can be born a male with a degenerating y chromosome. Chromosomes alone do not make you female or male. Nature doesn’t get it perfect every time.
      As a medical professional myself I have to say that I’m appalled by your answer.
      Looking at somebody who is transgender who has an XY chromosome but is female who is hermaphrodite or not I’m binary should not be as black and white as you make it because nature is not black and white it is not cut and dry. There’s always variations to everything and there’s variations to sex I mean did you even read that article? The platypus has 10 sex chromosomes and could be missing leak between an XY and a ZW? Did you read that part? Or did you decide to put your two cents in because you’re a doctor and you think you know it all?
      This in the medical profession is what we call the God complex. We’re one doctor has tried to save too many lives and thinks now that he can say one thing and it be true but no matter what you say it’s not true science proves that. You’re probably one of those doctors if they delivered babies that would do a genetic test on a child and at the chromosomes didn’t completely match up to the sex that that baby was supposed to be you might ask them to abort it or you may say this might be the best option I’ve met doctors like you I’ve worked with doctors like you.
      When are you guys going to learn that not everybody not every human being as evolution is proved is going to be the same in fact evolution is going to continue you think it stops with us you think that humans are the great creation? If we can go from Little things swimming around in the sea to legs walking on water to walking in the forest to procreating to being all one color to migration and then turning into different species of humans then it’s fair to think evolution is far from done with us. So it’d be extremely small-minded to be doctor to think that everything you know everything that you’ve learned will not adapt and change. If you haven’t learned anything from science class maybe you should have learned this energy is neither created nor destroyed it simply changes form and humans are nothing but energy, eventually we will evolve to something bigger or we will die out. And as it looks right now we are a virus we destroy everything in our path we cared about nothing but ourselves so it looks like we will die out and something bigger will evolve in our place but until then bodies will continue to evolve and new chromosomes will be found so everything that you’ve learned in medical school if you went to medical school will change eventually just like it has for centuries this isn’t the final word and everything the 2021 isn’t the end of medical research you don’t have the final say on anything and neither does the Bible.

    8. >if you have a penis, you don’t go in the women’s restrooms and vice-versa.

      Wrong. That’s simply not the case. Unless you plan on having genital inspectors in every restroom. Could be a lucrative new job.

      >which is either XY or XX. nothing more, nothing less.

      Scary that a supposed surgeon isn’t aware of Kleinfelters.

      >moving away from your self in order to feel like your self IS IN FACT a very bad mental state to be in

      Prove it

      > more people know what gender studies are than the are people who know what STEM even means

      Need a source on that one, cheif

      > the fact that this is even a thing to discuss sickens me.

      Ugh, yeah, imagine science studying things and adapting to new information. We shouldn’t discuss anything that isn’t intuitive, for… Science? I guess. Germtheory is bunk, it’s all humors. Our ancestors in science know that, no need to updat anything

  2. A couple different thoughts here, and I hope I can keep them coherent. All of the discussion of sex determination is interesting. I understand that certain species of plants and animals use different systems to determine biological sex. Also, that certain systems can be non-binary, etc. That being said, we are are not talking about bees, or melons, or fish or turtles. We are talking about human beings. XXY and XYY are mutations and defects of the genetic code. To use these disorders in an argument for non-binary gender is intellectually dishonest. The larger problem here really has nothing to do with gender. For the most part it is still OK to shame people for being fat, or poor, or not as smart, or just plain different. People will make fun and discriminate based on so many things. Growing up is hard, adolescence is hard, and there are a lot of challenges out there. Legislation that singles out trans people for humiliation are not good laws and are not good for society. That being said, I do not believe in non-binary fluid gender. I hate the use of the word “assigned” when talking about biological sex. Physically, you are either a boy or a girl, and anything else is an anomaly. But it’s probably good policy to have gender neutral bathrooms. It makes the line go more quickly. To Will’s point, my niece claimed that she is really a boy, and is transitioning FTM. She was always saying that she is lost, not fitting in, and that changing her gender would make everything better. She is an 18 year old girl, still developing as a person but now taking a whole bunch of hormones. And guess what? She is still lost, and doesn’t know what she is going to be doing with her life. Furthermore, the hormones have made her snarky and straight up obnoxious. Not fitting in can be very painful, but it would seem to me that when those around you don’t know who/what you are – that isolation would seem to be more painful. If you are feeling insecure about your identity, learn to accept yourself for who you are not transition into something that you are not. If the Queen of England had balls, then she would be the King……

    1. if they are claiming to be ftm then you should respect his choice to want to be called a him. you are chosing to make him uncomfortable because you refuse to believe something that is very true. you dont deserve to be related to that child because you dont even respect him enough to call him what he wants to be called. and if he is more comfortable transitioning then let him. it doesnt effect you in any way shape or form.

  3. I greatly appreciate this blog post. It’s very informative.

    Is there a good journal article that summarizes the current science on sex determination in humans that deals with all the various issues like SRY migrating to the X chromosome that can give rise to XX males and similar situations where XY individuals can turn out to be biologically female?

    1. While not amazing, this touches on a few things you mention.

      It touches on amniocentesis tests showing a pregnant woman can be XY. That ” DNA sequencing and cell biology are revealing that almost everyone is, to varying degrees, a patchwork of genetically distinct cells, some with a sex that might not match that of the rest of their body.” That cells can cross over during pregnancy, called microchimaerism. So an XY chromosomal child can gain XX cells from a mother and vice versa. A mother can gain XY cells from that child that can be active and form unique functions for the entirety of their lifetime. ‘Men’ can have cells from their mother active in their bodies.

      There is much more to this than chromosomes and I think we should be glad for that. This level of diversity is vital to our well being more than it is an issue.

  4. I agree with the gender as social construct thing. I don’t feel like a woman, or at least not the version of woman that society expects of me. In fact if anyone could tell me what it feels like to be a woman, please enlighten me. I am however a biological female and my life experiences are based on this fact. My hormones define my feelings, behaviour and actions, I cannot avoid it. As a biological female I have experienced inequalities based on having a vagina and a womb, not on what I identify as. My identity as a female is based on biology not on the whims of my mind. I don’t identify as a woman because woman is a gender construct and I wasn’t raised that way. That does not make me trans, a man in the wrong body, or any other such nonsense. I am still biologically female. And if I want to piss in a room that only allows other biological females in there why shouldn’t I be able to?

    1. Because being trans is not as u said…that’s all. This is much deeper than just not fitting into society. Even if we have one day equity into our society, trans would still be there. Because it has always existed, if u look into older societies we can find traces. But of course maybe there is people who r defining themselves as trans to escape the society, which is understandable. After all we r all different, let’s not forget that.
      Also, please note men will not being trans to rape anyone (ur case about bathroom seems so. Sorry). It costs way too much to do that. And they will not wait for that to rape anyone. Understand that.

      U feel u r a biological female, u r okay with this ? This is good for you. They don’t feel as they r in their defined gender, that’s all. And it is not based on society. They just know they r not fitting as u know u r fitting. This is THIS feeling u said. Please note this and don’t say this is ”nonsense”, try to hear them at least. To get a real idea of it. This is really dangerous to not help them.

  5. Okay, there are a few things I would like to clarify. One is that there are many gender abnormalities that happen, one of which is Klinefelters syndrome, which can still be identified genetically. What cannot be identified genetically is someone that is born as a girl with XX chromosomes and then somehow the girl is a boy. All forms of gender can be identified through an individuals genetic code and in the case of Klinefelters syndrome, it happens in .004 percent of the population. It is a medical anomaly as is any other genetic offset.

    Now, if an XY decides they are a girl and wants to have an operation to make themselves a girl, it does not change the fact that every cell in their body still identifies genetically as a male except for maybe some of their sperm cells. Furthermore, the discussion about equality is absurd. When males that decide they are female start raiding the female sports world, you will understand what I am talking about. But the inequalities work in both ways and neither sex is better than the other. Men are no better than women, and studies show that women are better at multi-tasking, tasks that involve social interaction, are more apt to be artistic, etc. Men really just carry the genetic strength that comes from the hormone difference of testosterone.

    There was a story I read about a 42 year old man trying to use a defense in court that he identified as a 14 year old girl. He was having sex with a 14 year old girl, so this whole thing was basically him declaring himself insane. He lost the case but the idea that an individual can identify as they please is insane. And as it is becoming more common, there are people that had spent their entire life identifying as a heterosexual female that all the sudden are a pansexual male because the people around them experimented with sex and determined that they have to be different. It was not a revelation, it was just someone feeling left out and wanting to be part of the what is going on.

    What makes my entire comment said is that someone will be offended by it. Genetics is able to tell the individuals sex and it has been that way for over a century. Stop trying to give excuses for people to identify in 400 different ways because it makes them feel better.

    1. You wrote: “ Now, if an XY decides they are a girl and wants to have an operation to make themselves a girl, it does not change the fact that every cell in their body still identifies genetically as a male except for maybe some of their sperm cells.”

      I am an 46XY FEmale. THAT WAS NOT SA DECISION I MADE. “Every cell in my body” is NOT “identifying genetically as a male.” My external genitalia is female. Until my hysterectomy, I had a uterus….the size of a walnut. I had Fallopian tubes and a cervix, albeit micro-sized. I had one ovary with no ova and one “streak” ovary — a one-dimensional , eighth-inch strip of non-egg bearing ovarian tissue.

      But neither you nor I nor the best current scientific studies can claim that “every cell in my body” identifies as male OR female. Life is not black and white.

    2. gender and sex are not connected, also transgender women tend to underperform in sports due to the incredibly low level of testosterone you have after HRT, it is lower than the average for cis women. the person who was declared insane happened because you cannot identify as a different age, it has nothing to with gender.

      you have no idea what you are talking about, you are just transphobic

  6. A very interesting article!

    Everyone seems to be focused on the possible political side of this posting. I understand there is an undertone of that, particularly with some of the intro, but what I got out of it was a fascinating documentation of reproductive methods across the animal kingdom. It even touched on cantaloupes at one point!

    I’m sure there’s much we don’t understand on these processes, and possible some things we have wrong. As with almost everything. It is amazing how many different systems there are in place for different types of animals. The honeybees and tortoise variation on what affected outcome of sex was something I’d never heard of before and was a bit dumbfounding to me. I actually laughed out loud when it was mentioned that Platypus have 5 pairs of sex chromosomes. I figured, of course they would. Very strange animals.

    It looks like the second link you’ve provided is the source material. I’ll be giving it a look.
    In the chance that is not your source material: citations would be appreciated.

    Thank you for the informative and entertaining writing.

  7. Contributing medically! sex determination system in a genome and how chromosome(xy and xx) are formed in male/female provided sperm and ovum during interface could tell that a supernatural being really molded, designed and created these hormones in human body!

  8. This was a great article to read. It is information rich while still being very enjoyable, which is not the case with all scientific papers. Dear God, some of the papers and books are so dry and dense it’s almost impossible to get through them. This is such an excellent blend of deep scientific research and juicy entertaining writing. Thank you.

  9. 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

  10. 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. <

  11. 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.

  12. 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.

    1. 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,

      this is the body God gave me

      … and He was right.

  13. 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.

    1. 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.

    2. 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.

      1. “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?

  14. 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”,

    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,

    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.

  15. 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

  16. Great article. That gave me some information i didn’t know, but also made sense. I’m not an educated scientist myself, only auto-didact. I enjoyed the article a great deal, though i am saddened that the whole comment section has turned into a whole political discussion about irrelevant matters. So much of the people around us, are influenced by mis-information, that they out right refuses sound science, and that why we have “flat earthers”, who believe Australia doesn’t exist, and Rome is a myth.

    Really people. If you have nothing constructive to say, shut the hell up. And leave science to those of us, who actually have an interest in science.

    Sorry, for my little outburst. Keep up the good work.

  17. The wording “by default” is an erroneous approach. What is his mistake? And the fact is that you just say, if the embryo is without a Y chromosome (i.e. there are no genes needed for the development of a female embryo), then the default gender is female. But if you think about it that way, it’s ridiculous. XY embryo – the default gender is male. A lot of genes are needed for the development of a female embryo. WNT4, DAX1, etc. And think for yourself. Why does the default gender need genes that suppress male genes?) DAX1 located on the X chromosome suppresses the SRY gene. XX males without a Y chromosome and SRY genes also exist. It turns out that the female gender is not the default gender of people. I am sure this also applies to birds, where the male is hardly the default sex. There is a whole pool of genes that control the hormonal environment, etc. And there is no default gender. For ovarian development, at least a WNT4 generator is needed. And the genes that are needed for the development of men are also located throughout the human genome (on autosomes) like genes, they are needed for women. Currently, science is gradually starting to move away from the “default” paradigm.

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