Most humans have 23 pairs of chromosomes. Twenty-two of these chromosomes are the same between males and females. The 23rd set are our “sex chromosomes.” (Getty Images)

Most humans have 23 pairs of chromosomes. Twenty-two of these chromosomes are the same between males and females. The 23rd set are our “sex chromosomes.” (Getty Images)

Gender aside, biological sex isn’t a dichotomy

Our biological sex characteristics and gender identities can be dynamic, and these variations enrich the human family.

  • Wednesday, August 11, 2021 1:30am
  • Life

By Lauren Gresham / Special to The Herald

Our reproductive anatomy is wildly more dynamic than you learned in school. Most of us were taught that people are either male or female, when in fact, humans are way more beautifully diverse than a strict biological sex dichotomy.

Most humans have 23 pairs of chromosomes. Twenty-two of these chromosomes are the same between males and females. The 23rd set are our “sex chromosomes.” Males typically have an XY pair and females typically have an XX pair. However, not all people have an XY or an XX set. Some people have an extra sex chromosome (XXY, Klinefelter’s Syndrome) and other people have only one sex chromosome (X, Turner’s Syndrome). Fascinating, right?

Having the classical XY or XX chromosome configuration still does not guarantee that someone will be stereotypically male or female. In order to fully develop as male, you need a functional gene called the SRY gene, which is located on the Y chromosome. However, in some people, this gene can get deleted or modified. That means someone can chromosomally be male, but because they do not have the genetic instructions to develop as male, they will appear to be female. Likewise, someone can have an XX chromosomal pair, but the SRY gene has migrated onto one of their X chromosomes. These folks have male genetic instructions and will therefore form male anatomy, but are actually chromosomally female. Who knew?

So, if you have the stereotypical chromosome pair and the associated presence or absence of the SRY gene, then you can be considered a typical male or female, right? Wrong! We also need functional estrogen and testosterone in particular amounts. The production of our sex hormones requires many enzymatic steps, and at each step, there can be differences. And even if we make our estrogen and testosterone as anticipated, some people have variations in their receptors for estrogen and testosterone, meaning that their cells may not listen to the messages from the sex hormones in the expected way. Furthermore, growing fetuses can be exposed to hormones or hormone-like substances during certain periods of development, which can create a whole other set of ways that people can be unique.

What I have been describing are some of the ways people can be intersex. Intersex is an umbrella term that describes individuals who have biological traits that fall outside the strict definitions of male and female. Like many people, I grew up thinking that biological sex was a dichotomy. You were either “male” or “female.” Well, it turns out that our physiology is significantly more diverse than these strict two categories. And intersex traits are common, making up around 1.7% of the population (as a comparison point, identical twins make up around 0.3% of the population). Intersex traits are as common as natural redheads.

Variations in reproductive physiology may be an odd choice for a health column, but from a societal lens, equality, representation and advocacy are all important factors that influence individual and therefore, community health. Many intersex folks have experienced medical trauma and erasure of their identities in pursuit of upholding a false biological sex dichotomy. And while transgender identities and advocacy is completely distinct from intersex health, folks in either of these categories can face similar harassment and discrimination. As a physician who specializes in working with transgender and gender non-conforming folks, I hear their narratives and struggles every day. Transgender health rights are under attack in this country, with more than 100 bills currently being proposed that would restrict access to care and equal rights for transgender and gender non-conforming individuals. Many of these bills, such as sports bans for transgender kids, may also have repercussions for intersex youth.

Biodiversity creates stability within ecosystems. One plant may be resistant to a certain pest, while another may be resilient to drought conditions. Diversity makes us stronger as a species. It is truly remarkable that both our biological sex characteristics and our gender identities can be so dynamic, and these variations enrich the human family!

Want to continue the conversation, have more to add, or learned something you would like to share? Please feel free to send me a message through my website,

Dr. Lauren Gresham is a naturopathic physician and a community health education specialist. Learn more about her by visiting

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