Throughout the existence of humanity, the various differences between males and females have been written in books, displayed in movies and plays, and simply discussed in everyday conversations. When discussed in conversations, it usually revolves around sports, job role distributions, or as playful banter. To anyone who has looked around themselves throughout their life, these differences may seem obvious and ludicrous to even discuss. However, recently, some of these differences have been called into question when discussing social issues, bringing front and center sports, work, and the line between comedy and insults. The differences aren’t absolute when comparing a single individual with another, and instead are considered to be average differences. Males shorter than the average male exist and females taller than the average female, or male, exist. However, all are part of the respective average.
Because of the physical differences, males and females have traditionally taken upon roles that fit their capabilities. Namely, males tended to go out and hunt or build structures and females tended to take care of the children and the community. There have certainly been many cases where females have filled the traditional male roles and males have stayed closer to home. There has even been in modern times an increase in the number of stay-at-home fathers and working mothers. This is likely due to a number of factors, chiefly among them the progression of technology allowing for less physically demanding work and more jobs that require mental, rather than physical, effort. However, on average the traditional roles are still filled by the respective sexes due to the physical differences. This isn’t to say that anyone should be forced into any role. Everyone should be free to choose what they want to do with their life. The traditional roles are just that, traditional.
Sex
The most basic differences between a male and a female are the visible external genitalia. A male is born with a penis and a female is born with a vagina. This is how doctors determine sex at birth. Additionally, the resulting chromosomes of an individual intended by nature are XX and XY. A female has XX chromosomes and a male has XY chromosomes. This is another marker typically used to determine the sex of an individual.
However, it turns out that development is more complex than penis and vagina or XX and XY chromosomes. A female’s egg always contributes an X chromosome and a male’s sperm contributes either an X or a Y chromosome. An X chromosome sperm meeting the egg starts the process of female development and a Y chromosome sperm starts male development. Human DNA contains 23 pairs of chromosomes for a total of 46. The 23rd pair contains the sex determining chromosomes. During normal development after the sperm meets the egg, DNA replication and cell division occurs and the chromosomes are copied to retain the same XX or XY sex determining chromosomes. The gonads, or testes in males or ovaries in females, are indifferent and will by default develop into ovaries. During XY development, a sex-determining region Y protein (SRY) of the Y chromosome initiates the male sex determination to develop testes. Sometimes improper development occurs, resulting in various sex-related conditions. This affects approximately 0.018% of the global population.1 Following are some examples.
- Androgen Insensitivity Syndrome: Cause by a mutation in the androgen receptor gene of the X chromosome. This results in an individual with male chromosomes, but external appearances can vary from full male characteristics to typical female characteristics.
- XY Complete Gonadal Dysgenesis, also known as Swyer syndrome: Occurs when the SRY is defective and fails to trigger the male determining process. This results in an individual with male chromosomes but female characteristics.
- XX male syndrome: An individual is born with XX chromosomes but male physical characteristics. Despite retaining male characteristics, individuals are sterile. This condition usually occurs when a Y chromosome accidentally transfers the SRY gene to the X chromosome during the meiosis stage of sperm cell formation. This results in the father producing some sperm cells that contain an X chromosome that have the SRY gene that triggers male development.
- 45,X/46,XY mosaicism: Occurs only during male intended development after a Y chromosome sperm meets the egg. Much or all of the Y chromosome in a cell can fail to duplicate during cell division. The resulting cell then continues the division process without the proper Y chromosome, leading to many improperly developed cells. The final outcome is an individual born with a mixture of chromosome groupings. Some cells contain the normal 46 chromosomes with the sex determining pair of X and Y, and other cells contain 45 chromosomes with the sex determining pair reduced to a single X chromosome. This development disorder can result in a wide range of characteristics, from a normal appearance individual to an individual of mixed sex characteristics.
- 45,X0, often called Turner syndrome: Females are born with only one X chromosome but still retain female characteristics and males are born without the Y chromosome but still retain male characteristics.
- 47,XXX, Trisomy X, or triple X syndrome: A female is born with an extra X chromosome. Typical physical female characteristics are retained, but individuals may have learning disabilities, minor dysmorphic features, increased height, or early menopause.
- 47,XXY, also known as Klinefelter syndrome: A male is born with an extra X chromosome. The individual contains all of the typical male characteristics, such as a penis and testicles, but may be infertile, have weaker muscles, less body hair, and greater breast growth compared to other males.
- 47,XYY, also known as Jacobs or Superman syndrome: A male is born with an extra Y chromosome. As with 47,XXY, typical male characteristics are retained, but the individual may be taller than average and have learning disabilities.
- 48,XXXX, or Tetrasomy X: Occurs when a female gains four copies of the X chromosome. Individuals can have a varying range of intellectual disabilities or physical conditions.
- 48,XXXY: A male is born with two additional X chromosomes. Individuals may have intellectual disabilities, sexual reproduction issues, and physical abnormalities.
Looking at the various development disorders, it is obvious that there are some individuals who don’t fit in the categories of penis or vagina or XX and XY chromosomes. An emerging belief is that sex is a spectrum. The debate comes down to a classical classification issue. On one side, the belief is that categorization is based on the intended natural human development, and that the very rare errors during the development process don’t change the standard definition of a human. The newly presented belief that one side has brought to the table is that because there are rare individuals who can’t be neatly fit into either the binary male or female categories, sex becomes a spectrum. Perhaps the driving factor behind this belief is the avoidance of the word disorder and the desire to instead consider every result as natural and not negative. Proponents of sex as a spectrum find the term disorder to have a negative connotation and would rather use the terms intersex or Variations of Sexual Development.2 3
“The point of the argument is not to determine which diagnostic language is superior, but to retain the hard-won right to secure for ourselves the ability to operate socially without the stamp of ‘disorder’ or ‘disease’ strictly delineating what counts as ‘truth’ with regard to embodiment.”
If it is believed that sex is a spectrum, classification becomes complex. Every aspect of a human would need to be considered a spectrum. Development defects can result in fewer or more limbs, fingers, heads, or other parts. Some are born blind, deaf, mute, with a cleft lip, with a hole in their heart, or numerous other possibilities. Using a spectrum for classification would throw out the idea of definitions based on intent, resulting in millions of types of humans. When a human heart is defined, it is based on the intended development. A congenital heart defect involving a hole is the result of an issue during pregnancy, but doesn’t add to the definition of a human heart. A coffee mug that has its handle accidentally broken off during production doesn’t cause the company to redefine the intended specifications of that particular product line to be mugs with handles and mugs without handles.
Perhaps classification is simpler when we define it by development intent, with errors simply being considered disorders. Disorders wouldn’t change the average definition and categorization of a human whose nature of development is to be born either male or female, to have two arms and two legs, and to have the ability to see, hear, and speak. The disabled community understands that being born in, or becoming, one of those different ways is a disability and they proudly wear that label. Disorders of sex development, intersex, or variations of sexual development are all just ways of defining what are, in truth, disorders. The medical community primarily uses the term Disorders of Sex Development to refer to errors during the development process, rather than including unintended developments within the binary intended human development categories of male and female to create a spectrum.4
Physical Differences
Outside of genitalia, likely the most obvious physical difference between males and females is height. It has long been observed that males are taller on average than females. Sometime between 384–322 BC, Aristotle wrote History of Animals and in this work described the physical differences between males and females among the various species.5 Aristotle found that “As a general rule, in red-blooded animals furnished with feet and not oviparous, the male is larger and longer-lived than the female”.
In 2002, Maciej Henneberg and Renata J. Henneberg studied the femora of 66 males and 100 females and the humeri of 61 males and 45 females, all from the ancient city of Pompeii. They found that the height range for males was 64 to 67 inches and for females 60 to 61 inches.6 Also in 2002, Damiano Marchi and Silvana M. Borgognini-Tarli studied the skeletal biology of two Italian peninsular Magna Graecia necropoles, Timmari and Montescaglioso. Their work analyzed 83 skeletons from 51 graves from the Greek colonized area of Southern Italy. Their finding was an average male height of 67 inches and a female height of 61 inches.7
Height differences don’t just stop at ancient people or modern observations in passing by individuals. It is worth having a look at recent studies from around the world. In the United States, the Centers for Disease Control and Prevention published a 2021-2023 study showing an average male height of 68.9 inches and an average female height of 63.5 inches.8 In February 2025, the Japanese Ministry of Education, Culture, Sports, Science and Technology published an average height for 17 year olds at 170.8 cm (67 inches) for males and 158 cm (62 inches) for females.9 A South African study published in 2016 showed that Black African males averaged 170.5 cm (67 inches) and Black African females averaged 158.7 cm (62 inches).10
If an informal collective consensus wasn’t enough, these studies make it clear that males on average have a larger height than females. Starting from the ancient people to the modern times, there is a several inch height difference between the sexes.
Another obvious externally visible difference is muscle mass. In a study of 468 men and women, the percentage of skeletal muscle mass compared to the overall body mass was determined. It was found that males average 38% and females 31%.11 This difference in muscle mass is one part in explaining why males more often take on more physical roles than females. It is also part of why males perform better in sports.
A less obvious difference is in the bone size and density difference between males and females. In one study, the bone density of 82 sets of opposite sex twins was analyzed. Opposite sex twins were chosen in order to have a more controlled situation where age, genetics, and upbringing were mostly the same. The study found that males have larger bones and more bone material because of the larger bone size, but that bone density was higher in the spine and hips among females and otherwise relatively the same between the sexes.12
Another interesting difference to consider is that of lung size. It has been found that males have 10 to 12% larger lungs than females.13 This is another part in explaining the difference in physical performance between males and females. Larger lung sizes have been found to be associated with longer endurance and better oxygen delivery to fuel the muscles.14
Personality
The differences between males and females may not end at the physical form. Differences in expression and personality between males and females have also been observed. Are these differences biological in nature, cultural and influenced by how someone is raised, or a mix of both? To simplify to a common phrase, is an individual’s personality nature or nurture, or a complex mixture?
There are conflicting studies and opinions as to whether there are differences between the workings of male and female brains.15 16 Because of this, there isn’t yet enough information to conclusively state either way through drawing upon evidence. It is clear, however, that over the course of human existence people have observed common differences in behavior between boys and girls, and men and women. At play, boys tend to gravitate toward physical manipulation activities such as playing with blocks or toy cars. Brothers can often be found play wrestling with each other, or playfully tormenting their sister. Girls gravitate toward social activities, animals, and can also be found playing dress up. Many parents will state in agreement with other parents that their boys are or were more active and rowdier than their girls.
The trend continues into adulthood where men enjoy cars, watching sports, and more action-based video games. Women enjoy social functions, gardening, and life simulation video games. These personality traits aren’t set in stone for every individual, since some men enjoy gardening and some women enjoy cars. But the differences are what have been found to be the average between males and females. For many people to have noticed these same differences, maybe it means that there are indeed brain differences. If not, then it must be a complex situation involving learned behavior from parents, friends, or videos. It may be useful to have a study involving single mothers and single fathers of various types, including those with kids who attend school, those who home school, and those from cultures who don’t watch much entertainment.
- https://www.clinsurggroup.us/articles/IJCEM-10-161.php ↩︎
- https://www.euppublishing.com/doi/10.3366/soma.2011.0026 ↩︎
- https://adc.bmj.com/content/91/7/554.responses#variations-of-sex-development-instead-of-disorders-of-sex-development ↩︎
- https://publications.aap.org/pediatrics/article-abstract/118/2/753/69039/Summary-of-Consensus-Statement-on-Intersex?redirectedFrom=fulltext ↩︎
- https://classics.mit.edu/Aristotle/history_anim.4.iv.html ↩︎
- https://www.academia.edu/36649697/Reconstructing_medical_knowledge_in_ancient_Pompeii_from_the_hard_evidence_of_bones_and_teeth ↩︎
- https://www.academia.edu/212148/The_skeletal_biology_of_two_Italian_peninsular_Magna_Graecia_necropoles_Timmari_and_Montescaglioso ↩︎
- https://www.cdc.gov/nchs/data/series/sr_03/sr03-050.pdf ↩︎
- https://www.mext.go.jp/content/20250213-mxt_chousa01-000040132_1.pdf ↩︎
- https://pmc.ncbi.nlm.nih.gov/articles/PMC5244443/#:~:text=agreement%20between%20measurements.-,Results,sd%206%C2%B71)%20cm. ↩︎
- https://pubmed.ncbi.nlm.nih.gov/10904038/ ↩︎
- https://pubmed.ncbi.nlm.nih.gov/12830370/ ↩︎
- https://pubmed.ncbi.nlm.nih.gov/12773331/ ↩︎
- https://pmc.ncbi.nlm.nih.gov/articles/PMC5023719/ ↩︎
- https://www.pnas.org/doi/10.1073/pnas.2310012121 ↩︎
- https://www.nytimes.com/2018/12/03/opinion/male-female-brains-mosaic.html ↩︎
