Biological Sex, from an Introduction to Human Sexuality Instructor

I hear people try to talk about "biological sex" and I shake my head because it’s clear that they don’t actually know what they are talking about. There are, at minimum, three ways to biologically define sex (1.  Chromosomes & Genes  2.  External Genitalia  3.  Internal Reproductive Organs), and any or all of these may differ from the other two biological definitions.  And we’re not even going to talk about gender identity, which can also differ from the three definitions, too!  So, when someone says anything about biological sex and doesn't talk about at least a couple of these biological markers, then they are basing their biological knowledge off of their kindergarten teacher forcing kids into lunch lines based on boys and girls.  

I’m a psychologist, not a biologist or geneticists, so this might be pretty simplistic, but here's the most elementary definitions of sex and gender that we go over in my Human Sexuality course.  This blog will only discuss definitions of biological sex, but it’s important to understand that biological sex does not always correspond to gender identity.    

• Sex (male or female):  The biological and physical sexual organs that you are born with.  I include genes and chromosomes in this definition.
• Gender or gender identity (man or woman):  The gender that you feel that you are, the gender that you most identify with.

Chromosomes & Genes: 

Usually, but not always, humans are XX (genetic female) or XY (genetic male).  Chromosomes are really powerful because they determine which hormones are released.   

Cases when chromosomes are not XX or XY:  

However, there are a couple of syndromes in which a person is neither XX nor XY.  If you hear someone say, “You’re either a male or a female based on your genes!” you can let them know that that isn’t true!

·         Klinefelter’s Syndrome:  Condition in which genetic males have an extra X chromosome (XXY).  Some people with this syndrome express their gender identity as women, and some as men; there isn’t a clear pattern of gender identity based on this genetic make-up.  People with Klinefelter’s tend to:

o   Be tall (like many males)

o   Not be that muscular (like many females)

o   Have breasts and hips (like many females)

o   Have a small penis and testicles (like many males)

o   Have low sexual desire 

·         Turner’s Syndrome:          A condition in which someone has only one X chromosome (XO).  Almost all people with this syndrome express their gender identity as women even though they don’t have ovaries, so they don’t have the hormones to begin puberty as a woman (menstruation, breasts, hips, etc.).  Thus, they are not exactly genetically female and their internal reproductive organs aren’t fully developed, but their gender identity is as a women.

Even at the most basic level of our chromosomes, there is no male/female binary.  Although you might hear this, people are not only XX or XY. 

External Genitalia & Internal Reproductive Organs:         

Sex hormones, like testosterone, are released prenatally and affect development of sexual organs and the brain.  If testosterone is not released, then external genital and internal reproductive organs develop as female (female is the default).  Ambiguity of genitals is due to these hormonal influences (or lack of influences) in the womb.  People with ambiguous genitals usually have genes that are XX or XY (not one of the syndromes above).  Thus, these people are not genetically ambiguous.  

True hermaphrodites are rare; a hermaphrodite is a person with both male and female reproductive systems.  Some use the term intersex now, but that term also has various meanings.  Hermaphrodites are usually genetic females (XX), but one side of their body has male organs (a testicle, vas deferens and/or epididymis), and the other side has female organs (a Fallopian tube and an ovary).  The external genitalia tend to be ambiguous, meaning that it is unclear if the baby has a large clitoris or a small penis, so you might not know that your child was intersex until puberty or a doctor was looking at their external organs.  In the past, doctors have surgically shortened these micro-penises and had the child raised as a girl. 

Cases when external genitalia are ambiguous:  Pseudohermaphrodite

A pseudohermaphrodite is a person born with ambiguous genitalia, although they are genetically one sex or the other (XX or XY).    

·         Androgenital Syndrome (AGS):      Condition in genetic females (XX) in which the adrenal glands excrete too much testosterone during fetal development, causing masculinization.  These people tend to identify as women (their gender identity), but their clitoris and labia are enlarged so doctors might mistake them for a boy with a small penis and small testicles when born.  In this case, the genetic sex and gender identity usually match, but the external genitalia are ambiguous so they might be mis-gendered at birth. 

·         Androgen Insensitivity Syndrome:  Condition in which the tissues of genetic males (XY) do not respond to testosterone (that’s the “insensitivity” part).  As a result, a clitoris, labia, and short vagina develop (because female is the default), but the internal female structure does not develop.  The gender identity tends to be as a woman and the external genitalia is female, even though the genes are male.

People who say “girls have vaginas and boys have penises” are again inaccurate because external genitalia are a lot less clear than we think, and they may or may not match the internal organs (or the person’s chromosomes). 

Conclusion

In sum, not only do our biologically markers (genetics, external genitalia, or internal organs) sometimes not all indicate the same sex, but none of the biological definitions of sex have only two options.  Sure, these conditions are rare, but that doesn’t make them less true!

• You may be XX or XY or something else!
• You may have male genitalia or female genitalia or external organs that are ambiguous!
• And, rarely, people can have both male and female external genitalia! 
• You may have internal reproductive organs that are undeveloped or male or female (or, rarely, both male and female), or, like me, have had them removed!

Birth certificates are inaccurate indicators of biological sex since chromosomes and internal organs are not tested at birth and external organs can be ambiguous.  And since there is not one definition of biological sex, it might be best if we just believe people when they tell us their gender identity and call it a day.