Can Archaeologists Really “Disprove” a Transgender Person’s Gender Using Their Skeleton?

People who oppose the idea that transgender people should be allowed to exist and have rights often promote the claim that archaeologists can determine a person’s “true sex” based solely on their skeleton. They claim that, by examining a trans woman’s skeleton, archaeologists in the future will be able to prove that she was “really” a man and that, by examining a trans man’s skeleton, these archaeologists will be able to prove that he was “really” a woman. They claim that this proves that trans people are delusional and their genders are invalid.

In this post, I will show that the argument I have just described is hopelessly wrong on many levels. First, I will show that sex and gender are two different things and that a person’s skeletal structure says absolutely nothing about their gender. Second, I will show that guessing a person’s sex from their skeleton is actually much more complicated than opponents of trans rights regularly portray it. Third, I will show that, at least in some cases, a transgender person’s skeleton may actually be noticeably different from the skeleton of a cisgender person of the sex the trans person was assigned at birth.

Fourth and finally, I will show that reducing a person’s biological sex to their skeletal structure is extremely reductive and misleading, especially since gender-affirming hormone replacement therapy (HRT) can cause drastic, scientifically observable, physical changes to many other aspects of a person’s body, including their brain.

A common transphobic talking point

Fair Play for Women is a U.K.-based political activist group that opposes rights for transgender people under the guise of what they call “gender critical feminism.” They have a whole post on their website published on 7 July 2017 titled “Biological sex differences: bones & muscles,” which is dedicated to trying to prove that men and women are innately biologically different and that this means trans people’s gender identities are invalid. The post specifically cites the ability of archaeologists to identify the sex of a person from their skeleton as supposed “proof” that trans people are delusional:

“The biological sex of an adult skeleton can be determined with 95% accuracy by measuring the hip bones alone, 83% accuracy by the skull, and 80% accuracy by the long bones (femur & tibia).”

To give another example, in 2020, someone made a post in the subreddit r/IAMALiberalFeminist with the tag “Gender Critical” and the title “Differences in Male and Female Skull” with a diagram that shows a skull with features that are conventionally considered male alongside a skull with features that are conventionally considered female. The sexually dimorphic features shown in the diagram are real, but the diagram greatly exaggerates them for visual effect. In real human skulls, sexually dimorphic features are usually far less obvious.

In a comment directly beneath the aforementioned post, someone else remarks:

“In college I took a forensic anthropology class and learned the very basics of how to identify human bone fragments, including sex. I remember the sex differences particularly in the skulls and pelvic bones. It was an interesting and challenging class.”

“Here’s the deal: if someone’s remains, God forbid, need to be identified by a forensic team, you better believe that they are going to identify their biological sex if they can. Asserting that you are of another sex than you biologically are doesn’t matter in these situations. Biological sex has a basis in reality no matter what anyone tries to convince you.”

These are just a few examples of the talking point in action. I could cite more examples of it, but I am not going to because they would just be repeating the exact same claim.

ABOVE: Screenshot of the Reddit post referenced above showing exaggerated sexual dimorphism in human skulls as supposed evidence that trans people’s gender identities are invalid

People who oppose trans rights apparently use this argument so frequently that trans people themselves commonly share memes making fun of it. For instance, r/traaaaaaannnnnnnnnns is a subreddit for trans people to share memes “making fun of themselves, others, and the situations they find themselves in.” I don’t really follow the subreddit all that closely, but I have occasionally scrolled through it from time to time and, from what I’ve seen of it, memes making fun of the transphobic talking point about future archaeologists finding trans people’s skeletons seem to be a regular staple.

I will share just a few examples of this kind of meme that have been posted in the past few weeks. Below is a screenshot of a meme posted in the subreddit on 12 March that has a transphobe randomly telling a trans person that archaeologists will find their skeleton and “know” that they are “really” the sex they were assigned at birth. The trans person responds with a giant thumbs-up and goes back to what they were doing.

ABOVE: Screenshot of a meme posted in r/traaaaaaannnnnnnnnns on 12 March 2022

Below is a meme posted on the same day that similarly has a transphobe randomly telling a trans person that archaeologists will find their skeleton and know their sex assigned at birth. This time, the trans person responds by simply ignoring them. The transphobe tries to pester them again, but the trans person continues to ignore them. Finally, the transphobe starts angrily shouting at the trans person.

ABOVE: Screenshot of a meme shared in r/traaaaaaannnnnnnnnns on 12 March 2022

Finally, here is a meme posted on 14 March in which the author of the meme says that they are going to have a so-called “Viking funeral” so that they won’t leave behind any bones for future archaeologists to find that they might be able to use to misgender them.

As I discuss in this post I made in February 2020, there is actually no historical evidence to suggest that the medieval Norse ever really gave people funerals by sending them out to sea in a boat and then setting the boat on fire with a flaming arrow. In fact, the odds of a flaming arrow fired from a significant distance successfully hitting a boat and setting it on fire are slim to none. The meme is still pretty funny, though, as long as you aren’t overly analytical about it like I always am.

ABOVE: Screenshot of a meme shared in r/traaaaaaannnnnnnnnns on 14 March 2022

Sex: neither binary nor immutable

Given that this talking point seems to be so common, in this post, I want to explain in depth precisely what is wrong with it. Let’s start out by defining a couple of important terms that have already come up and that will continue to come up throughout the rest of this post.

The word sex refers to a person’s biological characteristics that can be observed or measured. The word gender refers to a person’s social and cultural identity or role as a woman, man, or nonbinary person. I talk about the complexities of sex and gender at much greater length in this post I wrote back in March 2021, which I highly recommend reading to anyone who is interested, but I will summarize some of the most important points here.

People who publicly oppose trans rights like to claim that they simply believe that biological sex is “real” and that people who support trans rights deny that it is “real.” This, however, is a willful and blatant misrepresentation of the nature of the debate. I do not know of anyone currently alive on earth who denies that biological sex is a thing that exists. I know a lot of trans people and every trans person and trans ally I know of acknowledges that biological sex exists.

The real difference between people who oppose trans rights and people who support trans rights is that people who oppose trans rights believe that biological sex is binary and immutable (i.e., unchangeable) and that a person’s gender is automatically determined by their biological sex. People who support trans rights, on the other hand, hold that these three assumptions are incorrect.

The talking point that future archaeologists being able to identify a trans person’s sex assigned at birth from their skeleton somehow disproves the person’s gender only makes sense if someone already believes all three of the assumptions that opponents of trans rights hold. As I will now demonstrate, opponents of trans rights are wrong, supporters of trans rights are correct, and the talking point about archaeologists is therefore based on a false premise.

Sex is much more complicated than a simple binary of “male” and “female” and it has many complex, interrelated aspects. Some aspects of a person’s sex include their chromosomes, their hormones, their physical anatomy, their ability or inability to produce certain kinds of gametes, and so forth.

Some people are born intersex, meaning they are born with biological characteristics that do not fit conventional notions of “female” and “male.” Instead, they are born with some combination of biological characteristics that are typically associated with one sex and others that are typically associated with a different sex. There is a whole plethora of different ways this can happen and many different intersex variations, proving that sex is not a simple binary, but rather a complicated spectrum.

Sadly, the medical establishment has wrongly pathologized intersex people. It is routine practice for doctors to perform medically unnecessary surgeries on children with certain intersex variations shortly after they are born or while they are still very young, long before they are able to give any kind of informed consent, to make their reproductive anatomy look more like what is considered “normal” for a male or a female. Currently, one of the main goals of intersex rights activism is to stop these medically unnecessary, nonconsensual surgeries on intersex children.

ABOVE: Diagram from Wikimedia Commons illustrating a sagittal view of what is considered a typical female reproductive system (left) and diagram from Wikimedia Commons illustrating a sagittal view of what is considered a typical male reproductive system (right). Reproductive anatomy is just one aspect of a person’s sex and variations in it are more common than you might expect.

Sex is not immutable either. As I will discuss in much greater detail later in this article, some of a person’s sex characteristics can change over the course of their life, either naturally or through human efforts. A transgender person who has been on hormone replacement therapy for a significant length of time is actually physically and biologically different from a cisgender person of the same sex that the trans person in question was assigned at birth.

Of course, to be very clear, no reasonable person who knows what they are talking about will claim that a trans man is biologically identical to a cisgender man, nor will any reasonable, well-informed person claim that a trans woman is biologically identical to a cisgender woman, since, in both cases, there are undeniable biological differences.

I have never personally met a trans person who does not acknowledge this fact. I am sure that there are probably really a few trans people out there somewhere who think that they are biologically identical to cisgender people of their gender identity, but those people, if they exist, are a very small, very fringe minority.

In fact, if I were to make a subjective assessment based on the trans people of whom I personally know, I would say that trans people actually tend to be significantly more conscious than the vast majority of cisgender people are of the physical differences that exist between themselves and cisgender people of the same gender. For many trans people, these physical differences are a major source of gender dysphoria (i.e., pain or discomfort with characteristics related to the sex a person was assigned at birth), which is precisely what motivates the majority of trans people to transition in the first place.

Gender is not necessarily determined by biological sex

This brings us to gender. The anti-transgender position that a person’s gender is automatically determined by their chromosomes, their genitals at birth, their bone structure, their ability to produce a certain kind of gamete, or what it says on their birth certificate is philosophically untenable and is disproven on many different grounds. As I have already argued in my post from last year that I have already linked, although sex and gender are related, neither of these things necessarily determines the other.

Arguably the main problem with the anti-transgender position from a theoretical standpoint is that it tries to dictate how a person is allowed to live socially based on factors that have little or no relevance in the vast majority of social contexts. I’ll start with chromosomes. Proponents of the anti-transgender position love to claim that these are what defines a person’s gender, but yet a person’s chromosomes are microscopic and completely socially irrelevant. Indeed, basically the only social situation I can think of in which a person’s chromosomes could be relevant is if the person has a chromosomal abnormality that they need to talk about.

Historically speaking, the notion that gender has anything at all to do with chromosomes is a very recent invention, since, for the vast majority of human history, no one knew that chromosomes even existed. Sex chromosomes were only first discovered in 1905, meaning scientists have only known about their existence for a little over a century at this point.

ABOVE: Size comparison from the website Punnett’s Square showing a human X chromosome (left) and a human Y chromosome (right)

Even today, it is not even possible to know for certain which chromosomes a person has unless they have had a sample of their DNA tested in a lab. There are intersex cisgender women who have conditions like complete androgen insensitivity syndrome (CAIS) or XY gonadal dysgenesis (also known as Swyer syndrome) who have XY chromosomes, despite having been assigned female at birth, having naturally female features, and regarding themselves as women. (Those with CAIS are also born with internal, undescended testes.)

Meanwhile, there are intersex cisgender men who have XX male syndrome (also known as de la Chapelle syndrome) who have XX chromosomes, despite having been assigned male at birth, having naturally male features, and regarding themselves as men. There are also intersex people with other chromosomal combinations.

There are documented cases of people who have intersex chromosomal variations who either only found out about it in adulthood or never found out about it at all in their whole lifetime. For all we know, there may be transphobes out there who go on and on about how chromosomes dictate a person’s gender who unknowingly have a different set of chromosomes from the one they think they have.

ABOVE: Photograph from Wikimedia Commons of a group of women with androgen insensitivity syndrome and related conditions. All of these women have a Y chromosome, but they have naturally developed with female appearances.

What sort of genitals a person had when they were born is likewise completely irrelevant to the vast majority of social situations in the present, especially since their genitals may have changed since the time when they were born. Indeed, even what sort of genitals a person has currently is irrelevant to the vast majority of social situations, since, the vast majority of the time, other people are not going to be seeing or interacting with their genitals in any way. (I personally honestly cannot remember the last time anyone other than I myself even saw my genitals; all I can say is that it has been many years.)

A person’s internal reproductive anatomy is really only socially relevant in three situations: 1) if there is some kind of medical situation involving that anatomy, 2) if someone is menstruating (which can occur in most, but not all, people assigned female at birth who are of reproductive age) or they are talking about menstruation, or 3) if someone is trying to produce offspring. A person’s ability to produce a certain kind of gamete is only ever socially relevant in one situation, which is if the person in question is trying to produce offspring.

It is plainly nonsense to say that any of the more-or-less socially irrelevant factors I have mentioned above should dictate what socially constructed gender group a person is allowed to belong to, what kind of name people should call them, what pronouns people should use to refer to them, how the person should be allowed to interact with other people in gendered situations on a daily basis, how other people should interact with them, what kind of clothes they should be allowed to wear, how they should be allowed to wear their hair, which restroom they should be allowed to use, what hormones they should be allowed to put voluntarily in their body, or what kind of genitals they should be allowed to have.

The anti-transgender position also blatantly ignores what is the lived reality for many trans people. The fact of the matter is that there are trans people who are successfully living as their gender identity, including trans people who pass completely as their gender, who are automatically regarded as their gender by everyone everywhere they go, and who are, for most social purposes, no different from cisgender people of their gender.

Proponents of the anti-transgender position, however, insist that such trans people are not “really” the thing that everyone else recognizes them as, on the basis of socially irrelevant attributes that no one interacting with them in person on a daily basis can even detect.

So, what is gender?

Since I have discussed what gender is not, I suppose I should say a few words about what gender is. This is a somewhat more difficult question to answer, because there are many different philosophical interpretations and theories that have been applied to gender.

One theory that tends to be popular among professional academics who study gender is one that was first proposed by the American philosopher Judith Butler (who identifies as non-binary and uses they/them pronouns) in their influential book Gender Trouble: Feminism and the Subversion of Identity, which was first published in 1990 by Routledge.

Butler argues that every society has norms and expectations for how a “woman” or “man” is supposed to look, sound, speak, and act. They argue that an individual person’s gender is not an innate identity, but rather a role that is created through a person’s constant, usually unconscious performance of actions and forms of self-presentation in conformity with or defiance of culturally-specific, constructed gender norms.

Writing from this perspective, Butler adamantly rejects the idea that gender is necessarily fixed or that it is necessarily binary. They also hold that, because gender is created through performance, a person cannot have any kind of gender at all until they start performing gendered acts. (They include speech acts, such as declaring oneself to be of a certain gender or non-gender, within the category of gendered acts.)

ABOVE: Photograph from Wikimedia Commons of the American feminist philosopher and gender theorist Judith Butler (left) and front cover of their 1990 book Gender Trouble: Feminism and the Subversion of Identity (right)

How this ties back to archaeology

Now that I think I have shown that the assumptions underlying the anti-trans talking point are false, let us return to how this relates to archaeology. It may be possible for archaeologists to guess a person’s sex from their skeletal remains, but a person’s skeleton does not necessarily say anything about their gender.

It is true that it has been common for archaeologists in the past to assume that a person with a skeleton with features that are conventionally considered “male” was necessarily a man and that a person with a skeleton with features that are conventionally considered “female” was necessarily a woman. Most archaeologists nowadays, though, are aware enough of the distinction between sex and gender that they are much less likely to make these mistaken assumptions.

Nowadays, when archaeologists find a skeleton, they usually try to assess the person’s gender based on where the person was buried and what kinds of objects they were buried with. If there is an inscription or grave marker or something that indicates the person’s name, archaeologists can tell usually tell the person’s gender from their name.

If there are grave goods, archaeologists can use the kinds of objects that are included among the grave goods to guess the person’s gender. Nonetheless, archaeologists are well aware that grave goods do not always reliably indicate gender, since a person might have been gender-nonconforming or, alternatively, they might be buried with objects that they never used in life.

For instance, friends or relatives of the person who were alive at the time of their burial might have left objects that they owned that they regarded as valuable in the person’s grave as a way of honoring the person. A person might also be buried with family heirlooms that belonged to an already-deceased family member of a different gender.

ABOVE: Illustration of the grave of the so-called “Birka female warrior,” published in 1889

How the human skeleton develops

Now that we have established the difference between sex and gender, let’s talk about how guessing a person’s sex from their skeleton actually works. A trained specialist in analyzing human remains can usually guess the sex of a cisgender, non-intersex adult human with a relatively high degree of accuracy if they are able to examine the person’s complete, intact skeleton. You may have noticed that this sentence contains a lot of qualifiers, and that is for very good reason.

Guessing the sex of a pre-pubescent child based on the shape of the child’s skeleton is generally at best only slightly more reliable than a coin flip, since the skeleton of male and female pre-pubescent children are so close to identical that even highly trained specialists find them nearly impossible to tell apart, even if the skeletons are both complete.

This, however, begins to change during puberty. During puberty, the gonads begin to produce sex hormones in much higher quantities than they did previously. There are two main kinds of sex hormones in humans: androgens (i.e., male sex hormones) and estrogens (i.e., female sex hormones). The primary androgen in humans is testosterone and the primary estrogen is estradiol. Testosterone is the primary hormone responsible for the development of male secondary sex characteristics and estradiol is the primary hormone responsible for the development of female secondary sex characteristics.

Every human being with fully functioning gonads has some amount of testosterone and some amount of estradiol in their body at all times. Both hormones fulfill important biological functions in people of all sexes. (For instance, we’ll talk more about the very important role that estradiol plays in skeletal development in people of all sexes in a moment.) The relative quantity of one hormone or the other, however, is usually determined by the kind of gonads that a person has. Generally speaking, people with testes have much higher levels of testosterone than estradiol and people with ovaries have much higher levels of estradiol than testosterone.

As a result of the differing levels of sex hormones, during puberty, a child with ovaries and a child with testes typically begin to develop different skeletal structures. This process, however, happens very gradually and at different rates in different people.

A specialist can generally guess the sex of an adolescent from bone structure with a higher degree of accuracy than the sex of a pre-pubescent child, but still not with as high a degree of accuracy as is possible when guessing the sex of an adult. As an adolescent grows closer to adulthood, skeletal dimorphism increases and it typically becomes easier for an expert to guess the adolescent’s sex based on their skeleton.

At the end of puberty, estradiol causes the epiphyseal plates at the ends of the long bones to seal, causing the bones to permanently stop growing. In people with ovaries, this usually happens between the ages of thirteen and fifteen. In people with testes, it usually happens a bit later, usually between the ages of fifteen and seventeen.

ABOVE: X-ray photograph from Wikimedia Commons showing the epiphyseal plates between the distal tibia and fibula of a twelve-year-old child

How the process of guessing an adult’s sex from their skeleton works

Before we discuss any of the specific features that are commonly used to guess an adult person’s sex from their skeleton, we should discuss how the process in general works. A person who has gone through female puberty and a person who has gone through male puberty have all the same bones with all the same basic structures, but the way these structures are developed tends to be slightly different.

Generally speaking, a person who has been though male puberty tends to have somewhat larger, more robust bones that are more developed around the areas where the muscles connect to the bone, while a person who has been through female puberty tends to have smaller, more gracile bones that are not as developed in muscle-connecting areas. There are also specific parts of bones that often tend to show more distinctive sexually dimorphic traits.

At the same time, though, there is considerable skeletal variation, even among individual adult humans who went through the same kind of puberty. Specific features in specific individuals may display a greater or lesser degree of sexual dimorphism.

When an archaeologist or forensic anthropologist is trying to guess a person’s sex from their bones, they typically assess each individual skeletal feature that is considered to display sexual dimorphism. They rate each feature on a scale from one to five, with a one being “most likely female” and a five being “most likely male,” with three additional points on the scale in between. Once they have assessed each feature, they assess the bones as a whole.

It is very common for individual skeletal features to be marked as threes on the scale, indicating that they are ambiguous and are not distinctly characteristic of a given sex. Sometimes the skeleton as a whole may be labeled “indeterminate” if it lacks sufficient sexual dimorphism to make an accurate assessment or if it displays too much of a mixture of traits.

The pelvis

By far, the most important bone structure for guessing the sex of an adult based on their skeleton is the pelvis, because the pelvis is by far the most sexually dimorphic bone structure in the human skeleton. If an archaeologist has the intact pelvis of a non-intersex human adult who did not have any kind of hormonal abnormalities, they can guess the sex of the person it came from with an extremely high degree of accuracy.

A study conducted by the anthropologists Marija Durić, Zoran Rakocević, and Danijela Donić, published in January 2005, titled “The reliability of sex determination of skeletons from forensic context in the Balkans,” found that an experienced anthropologist was able to correctly identify the sex of an individual based on the pelvis alone 100% of the time.

Typically, the pelvis of a person who went through male puberty is narrower and taller, with a higher iliac crest. The pelvic cavity is typically smaller and roughly heart-shaped. The pubic arch has an acute angle of roughly between sixty to seventy degrees, making a V shape. Meanwhile, the pelvis of a person who has gone through female puberty is typically broader, shallower, and roughly bowl-shaped, with lower iliac crests. The pelvic cavity is much bigger and shaped like a slight oval rather than a heart. The pubic arch has a less acute angle of roughly between eighty to ninety degrees.

ABOVE: Diagram I made myself using illustrations of male and female pelvises from the 1918 edition of Henry Gray’s Anatomy of the Human Body to show the differences between a typical male pelvis (left) and a typical female pelvis (right)

The skull

After the pelvis, the next most sexually dimorphic bone structure in the human body is the skull, which is significantly less sexually dimorphic than the pelvis. The skull still contains some sexually dimorphic features that can most commonly be used to guess the sex of the person to whom the skull belongs, but female and male skulls resemble each other much more closely than female and male pelvises.

It is possible for even a highly experienced expert to misidentify the sex of an individual based on their skull alone. The same study by Marija Durić, Zoran Rakocević, and Danijela Donić that I cited earlier found that, based on the skull alone, the experienced anthropologist was able to correctly identify the sex of an individual 70.56% of the time.

The skull of a person who went through female puberty is usually smaller and more gracile overall. The top of the skull is usually more rounded and the sides tend to slope gently downward. The supraorbital ridge (i.e., brow ridge) is usually much smaller and less prominent, while the supraorbital margin is usually sharper. The zygomatic bone is less prominent and the mandible is more rounded.

The skull of a person who has gone through male puberty, by contrast, is usually somewhat larger and thicker overall. The top of the skull is typically blockier, the supraorbital ridge is more prominent, the supraorbital margin is more rounded, the zygomatic bone is more prominent, and the mandible is more squared.

ABOVE: Diagram I made myself using this photo from Wikimedia Commons to show the differences between a typical male cranium (left) and a typical female cranium (right)

The shoulders, torso, and femur

There are discernable sexually dimorphic tendencies when it comes to bone structures other than the pelvis and the skull, but these tend to be very subtle, more variable, and less reliable for determining the sex of an individual.

Generally speaking, a person who has been through male puberty usually has wider and higher shoulders than a person who has been through female puberty. A person who has been through male puberty usually has a shorter torso, but a longer, more robust femur. The femur of a person who has been through female puberty usually attaches to the pelvis at a more oblique angle, which can be observed by examining the end of the bone that connects to the pelvis.

ABOVE: Diagram from this article published in the journal Scientific Reports in 2020 showing the very slight, but observable, differences between the head of the average male femur and the head of the average female femur at age eighteen

Overall height

On average, people who have gone through male puberty are taller and have a larger frame than people who have gone through female puberty. The average height for a cisgender man in the United States is 175.3 centimeters (5 feet, 9 inches) and the average height for a cisgender woman is 161.3 centimeters (5 feet, 3¹⁄₂ inches).

Archaeologists can usually estimate an adult person’s height based on the measurements of certain bones. If they have the person’s complete skeleton, they can usually estimate the person’s height with an extremely high degree of accuracy. If the person is physically very tall and large, they are more likely to have gone through male puberty, while, if they are physically very short and petite, they are more likely to have gone through female puberty.

This is, however, only a general tendency, not a hard-and-fast rule, and I myself am a pretty clear example of an exception to the trend. I was assigned male at birth, I went through the full male puberty, and I am currently a twenty-two-year-old adult at the fullest height I will ever grow, but I am only 158.75 centimeters tall (5 feet, 2¹⁄₂ inches) and I have a very petite build. According to this “Height Percentage by Age Calculator for Men and Women in the United States,” I am shorter than 99% of U.S. men and 72% of U.S. women. The average woman is a full inch taller than me.

ABOVE: Photograph from Wikimedia Commons showing the so-called “lovers of Cluj-Napoca,” a pair of female and male skeletons found buried together in the cemetery of a former Dominican convent in the city of Cluj-Napoca, Romania, believed to have been buried there at some point between 1450 and 1550 CE. The slightly smaller skeleton on the left has been identified as female and the slightly larger skeleton on the right has been identified as male.

The bones of the hands and feet

The bones of the hands and feet also display some degree of sexual dimorphism. Regardless of overall height, the hands and feet of a person who has been through male puberty are typically proportionally larger than the hands and feet of a person who has been through female puberty.

According to this webpage, which cites data from three different studies conducted in North America in the late twentieth century, the average hand length for a person who has been through female puberty is 18.03 centimeters (7.10 inches) when measured from the crease at the bottom of the palm to the tip of the longest finger, the average hand breadth is 7.70 centimeters (3.03 inches) when measured at the thickest part of the palm, and the average foot length is 24.33 centimeters (9.58 inches) when measured from the end of the heel to the tip of the longest toe. The average hand length for a person who has been through male puberty is 19.02 centimeters (7.49 inches), the average hand breadth is 8.94 centimeters (3.52 inches), and the average foot length is 26.75 centimeters (10.53 inches).

There are, of course, plenty of variations and exceptions to the general trend. My own hands and feet are really tiny, even in proportion to my very small body size. My hands are only 16.5 centimeters (6.5 inches) long and only 7.62 centimeters (3 inches) wide and my feet are only 23.1 centimeters (9.1 inches) long, which means my hands and feet are actually significantly smaller than those of the average person who went through female puberty.

If an archaeologist were trying to figure out my sex assigned at birth based on my tiny hand bones without my pelvis or skull, I’m pretty sure they would conclude that I was assigned female. Meanwhile, there are plenty of cisgender women who complain about having big “man hands.”

Additionally, the relative lengths of the fingers on the hand can also be used as a clue to a person’s sex assigned at birth (albeit one that is not especially reliable). People who were exposed to higher levels of androgens while they were in the womb tend to have shorter index fingers than ring fingers, while people with lower levels of exposure to androgens tend to have index and ring fingers that are the same length or index fingers that are longer than their ring fingers.

Because of this, people assigned male at birth are much more likely to have shorter index fingers than ring fingers, while people assigned female at birth are more likely to have either index fingers of the same length or longer index fingers than ring fingers.

As I mentioned before, though, this is not an especially reliable indicator of sex assigned at birth, since there are many people assigned male at birth who have index fingers and ring fingers of the same length or longer index fingers than ring fingers and there are many people assigned female at birth who have shorter index fingers than ring fingers. My own index finger and ring finger are exactly the same length, which evidently means that I had low levels of exposure to androgens in the womb.

Interestingly, one study published in 2006 found that transgender women were significantly more likely to have female-typical digit ratios, which suggests that lower levels of pre-natal exposure to androgens may be a factor in influencing some people assigned male at birth to be transfeminine. (To be very clear, though, this does not by any means imply that all people assigned male at birth who had lower levels of exposure to androgens in the womb will turn out to be transfeminine; there are surely many factors involved, including genetic and cultural factors.)

ABOVE: Photograph I took myself of my left hand, with a ruler I borrowed from my parents, a book I happened to have on hand at my desk because I am using it as a source for the honors thesis I am writing, and a penny for scale

Kinds of gender-affirming hormone replacement therapies

So far, I have mostly been talking about cisgender, non-intersex people; trans people’s skeletons can be a bit more complicated. Before I talk about trans skeletons, though, I need to explain a little bit about how gender-affirming hormone replacement therapy (HRT) works. First, to be clear, not all trans people necessarily want to go on HRT. From what I’ve seen, though, the vast majority of binary trans people do eventually choose to go on it and a significant minority of nonbinary people choose to go on it as well.

Popular media coverage of trans people tends to fixate heavily on genital surgeries (which are often referred to somewhat euphemistically as “bottom surgeries”). It is true that many trans people do choose to undergo various kinds of bottom surgery, but there are also a lot of trans people who either decide not to have those surgeries or cannot afford them. HRT is far closer to universal among trans people than any particular kind of surgery. Even for those who do choose and can afford to undergo any of the various gender-affirming surgeries that exist, medical transitioning always starts with HRT.

Contrary to the narrative that people on the political right are trying to promote, under current medical ethics guidelines, pre-pubescent transgender children are never supposed to be given any kind of medical intervention; they do not receive any kind of surgery or hormones. For them, transitioning is exclusively social, not medical.

Once a transgender child enters pubescence, then, if it is legal in their jurisdiction, with their parents’ consent and a doctor’s prescription, they may be able to go on puberty blockers. These do not cause any changes to the body; they merely prevent the child from going through puberty for as long as the child continues taking them. They are generally considered safe and have been widely used for decades to delay the onset of puberty in cisgender children who begin puberty too early.

One of the most commonly prescribed medicines to block puberty is leuprolide acetate, which is typically administered via subcutaneous injection. It works by acting as an agonist (i.e., a competitor for the same hormone receptor) for the gonadotropin-releasing hormone (GnRH), which is the hormone that tells the anterior pituitary to release follicle-stimulating hormone (FSH) and luteinizing hormone (LH), which are the hormones that tell the ovaries and testes to produce estradiol and testosterone. Through this process, leuprolide acetate limits the amounts of both estradiol and testosterone that the gonads can produce.

Puberty blockers are useful in treating transgender pubescent children because they allow the child the chance to wait until they are older and more mature to decide if they want to begin cross-sex hormones, without forcing the child against their will to go through puberty and develop the secondary sex characteristics associated with the sex they were assigned at birth. (These secondary sex characteristics are the main source of body-related dysphoria for the vast majority of adult trans people.)

If the child decides at any time that they aren’t really transgender and they want to live as the gender associated with the sex they were assigned at birth, or they still consider themself transgender, but they decide they want to quit puberty blockers for some other reason, they can simply stop taking puberty blockers and go through puberty exactly the way they would otherwise.

ABOVE: Photograph from RxList showing a vial of leuprolide acetate meant for subcutaneous injection

Cross-sex hormone replacement therapy is only ever prescribed to older adolescents and adults. Generally, someone has to be at least sixteen to get a prescription for HRT and, even then, if they are under eighteen, they can only do so with their parents’ consent.

In some countries, getting a prescription for HRT is extremely difficult, even for an adult trans person. It often requires waiting on a list for many years and going through multiple sessions with a psychologist before someone can even be eligible. I have been told by trans people I know who live in the United Kingdom that, over there, all the waiting lists just to get an appointment to talk to a psychologist to maybe eventually go on HRT are all four years at the absolute minimum and some of them are as long as twenty years.

This means that, in the U.K., a person could try to schedule an appointment when they are a new parent in their early twenties and not actually get an appointment until they are in their early forties and their child is a fully-grown adult who is halfway through college. Meanwhile, here in the U.S., there are some clinics that operate on an informed-consent model where an adult person can schedule an appointment in as little as two weeks and go on HRT within only a few months.

HRT for trans men and transmasculine nonbinary people usually consists solely of testosterone, which is, as I mentioned earlier, the primary male hormone. In the U.S., it is most commonly prescribed in the form of a liquid that is designed to be administered via intramuscular injection.

ABOVE: Photograph from Wikimedia Commons of a vial of testosterone meant for intramuscular injection

Meanwhile, HRT for trans women and transfeminine nonbinary people usually consists of two medications. The first of these is estradiol, which is, as I mentioned earlier, the primary female hormone. In the U.S., estradiol is most commonly prescribed in the form of a small, blue, oval-shaped tablet that is meant to be taken orally.

Because testosterone is a much stronger hormone than estradiol, though, transfeminine people are normally also prescribed an antiandrogen (i.e., a medicine that blocks testosterone and other male hormones by acting as an agonist for the androgen hormone receptor).

In the United States, the most commonly prescribed antiandrogen for feminizing HRT is spironolactone, which is most commonly prescribed in the form of a large, round, pinkish-orange-colored pill that is usually described as “chalky” in taste and texture. In addition to its use in feminizing HRT, spironolactone is also commonly prescribed to treat acne and unwanted body and facial hair in cisgender women.

In countries other than the U.S., transfeminine people usually take a different antiandrogen known as cyproterone acetate, but cyproterone acetate is not approved for use in the U.S. because it can increase a person’s risk of developing blood clots, benign brain tumors, and liver damage.

ABOVE: Photograph of estradiol in oral tablet form (left) and spironolactone (right), the two medications that are most commonly used in feminizing hormone replacement therapy in the United States

The complexities of trans skeletons

If a trans person goes on puberty blockers before the cusp of puberty to prevent them from going through the puberty associated with the sex they were assigned at birth and, when they are old enough, they decide to go on cross-sex hormone replacement therapy, then they will go through puberty in a very similar way to how a cisgender person of their gender identity would—and their skeleton will develop similarly.

As a result of this, it would most likely be impossible for an archaeologist to distinguish the skeleton of a trans woman who never went through male puberty and only went through female puberty as an adolescent from the skeleton of a cisgender woman. Likewise, it would most likely be impossible for them to distinguish the skeleton of a trans man who never went through female puberty and only went through male puberty as an adolescent from the skeleton of a cisgender man.

If a trans person goes through the puberty associated with the sex they were assigned at birth, but they go on cross-sex HRT before their epiphyseal plates are fully sealed, their bone structure will stop developing in the manner of the sex they were assigned and birth and begin to develop more in the manner that is typical of the sex associated with the gender to which the trans person in question is transitioning.

A person’s bones cannot shrink once they have already grown. This means that, if a trans man has already grown a broad pelvis, his pelvis will not become any narrower. Likewise, if a trans woman has already developed broad shoulder bones, her shoulder bones will not become any narrower. A trans man whose epiphyseal plates have not yet sealed, though, will most likely start to develop broader shoulders and a trans woman whose epiphyseal plates have not yet sealed will most likely start to develop broader hips.

Finally, a trans person who goes on HRT after their epiphyseal plates have already sealed will not experience any significant changes in the size or overall shape of their bones as a result of hormone therapy. Some of the details on the surface of their bones, however, especially in the areas where the muscles connect to the bones, may gradually shift to become closer to what is considered typical for a person of the sex associated with their gender identity.

Some trans people choose to undergo facial feminization or facial masculinization surgery. What these kinds of surgeries involve naturally varies depending on the specific individual in question, but they often involve surgically reshaping certain parts of the person’s skull to make the person’s face more closely resemble what is considered typical for a cisgender person of that person’s gender identity. For a trans woman, for instance, it might involve a surgical reduction of the brow ridge, while, for a trans man, it might involve surgically enhancing the brow ridge.

At least in the United States where I live, these surgeries are very expensive, they are usually not covered by health insurance, and they carry some serious risks, including the risk of possible disfigurement, so most trans people either cannot afford them or do not want them. Nonetheless, they do exist and they are available to those who can afford them. (There are also, of course, the various genital surgeries that receive so much attention, but none of those involve any kind of bone alteration, so I will leave those aside.)

In conclusion to this part of my argument, the notion that there will never be any discernable difference between the skeleton of a transgender man and a cisgender woman or between the skeleton of a transgender woman and a cisgender man is simply untrue.

The extent to which a trans person’s skeleton will resemble what is considered typical for a person of the sex they were assigned at birth versus a person of their gender identity will depend on factors such as whether they are taking HRT, at what age they started HRT (assuming that they are taking it), and whether they have undergone any kind of surgery that has involved bone alteration.

A lot more to a person’s sex than just their skeleton

As one final note, it is essential to point out that the structure of a person’s skeleton is just one limited aspect of a person’s biological sex out of many. Indeed, it is one of the relatively few aspects of a person’s sex that are impossible or extremely difficult to change once a person has reached full adulthood. Reducing a person’s biological sex to nothing more than their skeleton and their chromosomes can be very misleading.

To show what I mean, allow me to briefly describe some of the very real biological changes that gender-affirming HRT causes in a trans person who has already gone through puberty and whose epiphyseal plates are already fully sealed. I’ll start by describing the effects of feminizing HRT and then I will describe the effects of masculinizing HRT.

Effects of feminizing HRT

Within the first month, feminizing HRT typically causes a transfeminine person’s skin all over their body to become thinner, softer, smoother, and less oily, resulting in a clearer overall complexion with less acne. It also decreases the melanin in their skin slightly, causing their skin tone to become slightly lighter in color. It causes their sweat glands to produce less sweat and the smell of their sweat itself to change.

Also usually within the first month, feminizing HRT causes those who are on it to begin to grow breasts. These will continue to develop over the course of the next year or more. Once they are fully developed, they will be fully visually, anatomically, and functionally identical to those of a cisgender woman and, under the right hormonal conditions, they can actually produce milk just like a cisgender woman’s breasts. (If a transfeminine person starts HRT after, say, roughly their mid-twenties, though, the size of their breasts is likely to be quite small, since they are past the age of prime breast development.)

Within the first two to six months, depending on genetic factors, most or all of the terminal hair on a transfeminine person’s body, apart from their underarm and pubic hair, may revert back to thin, invisible vellus hair. Even if it does not completely revert back to vellus hair, it will still become much thinner and lighter. Their facial hair will usually also become thinner and lighter, but it will not disappear completely. If the person in question has male-pattern scalp hair loss, this hair loss will cease its progression. In some cases, scalp hair that has already been lost may grow back, but this does not happen in all cases.

Within the first year, feminizing HRT causes a trans woman or transfeminine nonbinary person’s testicles to atrophy and shrink to less than half their original size. Sperm production will decrease and eventually cease entirely, although the precise point at which this occurs is highly variable. Some transfeminine people may permanently lose the ability to produce sperm within a matter of weeks; others may retain the ability to produce sperm for months or even years.

Their body fat will begin to redistribute into a feminine pattern, with fat being stored in the breasts, hips, and thighs more than in the gut. As a result of this global redistribution of fat, a transfeminine person’s face will gradually start to look more feminine; their cheeks and lips may become fuller, their chin may become more pointed, and their overall face may start to take on a more heart-shaped appearance.

Meanwhile, their muscle mass and strength will significantly decrease. As a result, tasks of physical strength that used to be easy may become more difficult or impossible. These last few changes will continue until they reach their maximum effect after about three to five years.

ABOVE: Photograph of Hunter Schafer, a trans woman who is an actress and model known for her role as Jules in HBO’s Euphoria (left) and Laverne Cox, a trans woman who is an actress known for her role as Sophia Burset in Netflix’s Orange Is the New Black (right)

Feminizing HRT also causes significant changes in a transfeminine person’s sexuality. Bear in mind that everything I am about to say is very generalized. Each person’s individual experience is unique, so, for some people, the sexual changes are very drastic, while, for others, they are less extreme. I debated whether or not to talk about this at all, but I feel it necessary to say something on this because it is an area in which the effects of HRT are especially evident.

Testosterone and estradiol both play important roles in regulating a person’s sex drive, but their respective effects on sex drive are different. These effects have not been formally well studied, but, anecdotally, higher testosterone levels tend to be associated with a greater incidence of feelings of raw, animalistic lust that are often cued by visual turn-ons. Higher estradiol levels, on the other hand, tend to be associated with a mellower, less urgent attraction that tends to be based less on visual cues and more on emotional and/or personal connection.

People with higher levels of testosterone often report feeling a constant, burning need for sexual gratification that only goes away right after they experience orgasm. The trans woman Natalie Wynn memorably describes the feeling of her own pre-transition libido in her YouTube video “Autogynephilia,” which she posted in February 2018, as “a demonic possession or alien infection.” The trans writer Ana Valens describes her own pre-transition libido in a post she wrote for The Daily Dot in November 2018 saying “sex constantly hummed in the back of my head like an idling engine.”

When a transfeminine person starts taking feminizing HRT, they usually find that this constant feeling of urgent, animalistic need for sexual gratification goes away within a matter of a few days or weeks. Gradually, though, usually within the first year and a half of HRT, a new sex drive establishes itself. Transfeminine people commonly describe their new sex drive after going on HRT as feeling less urgent, being less often cued by visual turn-ons, and being more often cued by feelings of emotional/personal connection to their partner.

A transfeminine person may also experience unpredictable changes in sexual and/or romantic orientation. It is very rare for someone to go from only being attracted to one gender to being only attracted to a totally different gender, but, anecdotally, many transfeminine people who thought they were only attracted to one gender before starting feminizing HRT report that, after starting it, they discovered that they are now attracted to other genders in addition to the one they were originally attracted to. In other words, HRT can sometimes make people realize that they are actually bi. This does not happen to everyone, but it does happen to some.

Feminizing HRT causes both the physical mechanics of sexual arousal and orgasm and the experience of these things to drastically change. It causes the skin of the penis to become softer and more sensitive. Trans women and transfeminine nonbinary people also find that it is much harder for them to become erect, the erections they do have are not as hard as their erections used to be, and sustaining an erection once they have one may be more difficult. Some transfeminine people are only able to have erections at all with the help of erectile dysfunction medication.

Ejaculation and orgasm also change. Transfeminine people on HRT usually describe orgasms as becoming harder to reach. When reached, they are usually more prolonged in their duration, but with less peak intensity. It is also very common for trans women to find that they gain the ability to have multiple orgasms in succession without a refractory period. Many trans women find that they lose the ability to ejaculate and instead come without ejaculating. If they do continue to ejaculate, the ejaculate itself changes from a large amount of viscous, white semen to a small amount of clear, colorless fluid.

Leaving those changes aside, there are a few notable things that feminizing HRT cannot do. As I mentioned earlier, it cannot make facial hair go away completely, so transfeminine people who want to permanently reduce or eliminate their facial hair have to go through laser hair removal and/or electrolysis, both of which are very expensive and generally quite painful. Electrolysis is far more expensive and is generally agreed to be far more painful than laser hair removal, but laser hair removal only works well if a person has dark hair on light skin, meaning, if a person has blond or red hair or they have dark skin, electrolysis may be their only option.

HRT also cannot cause the laryngeal prominence (commonly known as the “Adam’s apple”) to go away. Transfeminine people who want to get rid of their laryngeal prominence, though, can undergo a tracheal shave to remove it, which I am told is relatively affordable as far as gender-affirming surgeries go because it is a relatively simple procedure.

Feminizing HRT also cannot change a trans woman or transfeminine nonbinary person’s vocal cords, so it has no effect whatsoever on a person’s voice. Once the vocal cords have lengthened and thickened during male puberty, they cannot become shorter and thinner, except through vocal cord surgery, which is prohibitively expensive for most transfeminine people, is very risky and can have serious complications, and may not even be effective. For this reason, many transfeminine people instead go through vocal training, which can help them learn to speak in a passably feminine voice, despite having longer vocal cords.

ABOVE: Photograph from Wikimedia Commons showing the laryngeal prominence on an adolescent boy (which I have circled in red to indicate its location)

Effects of masculinizing HRT

Masculinizing HRT causes a trans man or transmasculine nonbinary person to experience exactly the opposite changes in all areas. Within the first two to six months, it causes their skin to become thicker, courser, and oilier, which may result in increased acne. It causes hair to begin to grow on their face, arms, torso, and legs. It also causes their sweat glands to begin to produce more sweat and their sweat itself to take on a more masculine odor.

Transmasculine people on HRT usually stop menstruating altogether within the first two to six months and virtually always stop menstruating by the end of the first year. Unlike feminizing HRT, which cannot change a person’s voice, masculinizing HRT does change transmasculine people’s voices. Within the first year, testosterone causes a trans man or transmasculine nonbinary person’s vocal cords to lengthen and thicken, causing their voice to become deeper, usually by about a full octave, and a laryngeal prominence to grow on their neck.

Testosterone also causes a transmasculine person’s body fat to begin to redistribute into a masculine pattern and their muscle mass and strength to increase. Physical tasks that were previously difficult or impossible may become much easier or possible. Transmasculine people who work out regularly often find they are suddenly able to bulk up muscles unlike any they were able to build before.

Testosterone can also cause breasts to atrophy and shrink to some extent, but it cannot make them go away entirely. For this reason, transmasculine people commonly undergo “top surgery,” which is a double mastectomy (i.e., the surgical removal of both breasts).

ABOVE: Photograph of Laith Ashley, a transgender man who went on masculinizing HRT when he was twenty-four years old and is now a model and actor

Masculinizing HRT also has significant sexual effects. Its effect on sex drive is notably the exact opposite of the effect of feminizing HRT. While transfeminine people report HRT causing their libido to become mellower and less urgent, transmasculine people on HRT regularly describe themselves as feeling constantly horny—much hornier than they’ve ever felt before—on a daily basis. They often find themselves getting turned on more frequently by visual cues. Like transfeminine people, transmasculine people may experience unpredictable changes in sexual and/or romantic orientation and in how they experience sexual attraction.

Reed Brice, a trans man, wrote a column for the website Healthline titled “U Up? How Does Hormone Replacement Therapy (HRT) Affect Your Sex and Libido?” In this column, he describes how his sexuality drastically changed after he started taking testosterone:

“Six months on testosterone, a hormone replacement therapy regimen I follow with an endocrinologist, had taken me from a slightly-above-average libido experienced by cisgender women in their early 30s, to a raging madness of thirst.”

“Many transmasculine people report this when they start HRT. The insanity probably sounds familiar if you’re currently going through puberty or looking back with mortified dread. That’s because hormone replacement therapy can feel like a second puberty.”

[. . .]

“After starting HRT, when it comes down to doin’ it, I’m increasingly physically and romantically attracted only to people as masculine, or more masculine, as I am. I discovered I can no longer function well in a strictly monogamous relationship, which is wild considering I’m a recovering serial monogamist.”

“I’m also far more open-minded than I used to be — if everyone is able and willing to consent, I’m fascinated to explore anything and everything my partner fantasizes about. As my body feels more correct, I enjoy sex more and worry about labels and expectations less. I feel like a different person sometimes!”

Masculinizing HRT also causes the external part of the clitoris to grow to several times its original length to resemble a miniature penis, which usually ends up being somewhere between one and three inches long. A trans man or transmasculine nonbinary person will usually also find that their clitoris becomes harder when erect and becomes erect more frequently. Meanwhile, the vaginal canal begins to atrophy and it mostly stops producing vaginal lubrication.

Effects of cross-sex hormones on the brain

In addition to the many obvious physical and behavioral changes I have described above, empirical studies have also found that long-term use of cross-sex HRT causes a person’s brain structure to gradually physically change to more closely resemble what is considered typical for the sex associated with the gender to which they are transitioning.

A review titled “Gender-Affirming Hormone Use in Transgender Individuals: Impact on Behavioral Health and Cognition,” published in the journal Current Psychiatry Reports on 11 October 2018 concludes based on an analysis of the findings of various studies:

“Among research that expressly examined the central nervous system and cognitive effects of GAHT [i.e., gender-affirming hormone therapy], most studies focused on tasks of spatial rotation and verbal fluency, namely those which have established sex differences, to determine whether transgender individuals are more similar to cisgender individuals with the same natal sex or to cisgender individuals with the same gender identity.”

“Using both cross-sectional and longitudinal design, the studies generally show that GAHT is correlated with changes in the direction of gender identity rather than natal sex with respect to global and regional brain volumes, white matter microstructure, and cognitive performance on sex-biased tasks requiring verbal and visual memory. To the best of our knowledge, no studies thus far have looked at how GAHT influences executive function and cognitive domains used for daily living.”

Clearly, even though HRT cannot change the structure of a person’s skeleton, it does cause some very real and, indeed, quite drastic biological changes, including changes to the structure of their brain. I think that a person’s brain is somewhat more consequential to an assessment of their sex than their skeleton. Unfortunately, soft tissues like the brain are rarely ever preserved for archaeologists to examine.

ABOVE: Photograph from Wikimedia Commons of a human brain