Let’s Talk About Sex, Or Should That Be Gender?
Let’s talk about sex, or should that be gender?
I confess to being a science nerd and am intrigued by most things science!
I was fascinated when psychologists said that there was no such thing as visual or auditory learners.
I read deeper when epidemiologists suggested a connection between large sporting events and an uptick in domestic violence.
And listening to the climate scientists? Well that got me onto my bicycle, composting and eating tofu.
But whilst I love reading others thoughts on these topics, I wouldn’t dream of writing a blog post on them because that’s not where my expertise lies.
I’m define myself as a physiologist where physiology is the science of the activities occurring within living things, the processes that help them to survive and thrive.
Physiologists use words like sex, male and female in a very specific way and I want my blog readers to truly understand what’s meant by these words.
Because it’s really easy and very common to be confused.
I’ve heard scientists (including shh, some colleagues!) get “sex” and “gender” mixed up on a regular basis so it’s no wonder, the rest of society is struggling with these words.
I suspect part of the issue is that people are a little shy of using the word “sex” and think that “gender” is a merely a more polite version of “sex”, that means the same thing – it isn’t and it doesn’t!
Okay, time to talk sex.
The first thing to know is that whilst the terms male/female refer to someone’s sex, these terms are really shorthand for “genotypic male and genotypic female”, which, in turn, are short for “genetically typical male” and “genetically typical female”.
(Phew, easy to see why we shorten those to male and female!)
But knowing the full version of the term, gives a good hint as to what determines our sex - yup, it’s our genes.
Not just any genes, but the ones making up the 23rd pair of chromosomes in each of our cells.
The cells of a (genetically typical) female all have 23 pairs of chromosomes in their nucleus and that 23rd pair will be made up of two, identical, X shaped, chromosomes in all females.
In (genetically typical) males, the two chromosomes of the 23rd pair in every cell don’t look the same because whilst one member of this pair is Y shaped, the second member is X-shaped.
(This difference in this 23rd pair is the reason why it’s males who determine the sex of all children but is also the reason why males suffer from a whole range of diseases from color-blindness to muscular dystrophy, that females escape from - definitely a great future blog discussion).
And because of this difference in the 23rd pair in our genetically typical females and males, we call this 23rd pair, written XX for females and XY for males. the sex chromosomes.
Not the gender chromosomes, definitely the sex chromosomes!
Let’s now go back to when each of us was young, really young, in fact about 4 weeks into our embryonic life when our mother had probably just found out she was pregnant.
At this stage all embryos look the same. Glance inside the abdomen of either a male or female embryo and we’ll see small swellings, called indifferent ridges, on both sides of the spinal column (backbone). And these indifferent ridges look exactly the same in both male and female embryos so that’s why they’re called – indifferent!
When the embryo is female, these ridges stay where they are and develop into ovaries, producing the eggs that will potentially allow this embryo to become a mother itself in a few decades time.
On the other hand, take a peek inside a male embryo, and we’ll see these ridges developing and move down into the scrotum, their new home outside of the body and where we now call them testes (testicles).
But to be clear, the default development plan for these indifferent ridges is for them to turn into ovaries.
The question, then, is that what nudges them in males to become testes?
Yup, it’s that Y chromosome.
And if there’s no Y chromosome?
It’s ovaries all the way!
The months have passed, and great news, we’ve had a safe (and quick!) delivery of a healthy baby.
And when we hear the midwife exclaim “congratulations, you have a beautiful baby boy”, we know that’s a rapid assessment based solely on the presence or absence of a penis - no one hastily carried out a quick genetic analysis in the delivery room.
It would be reasonable to think that a XY, genetically typical male will automatically produce a penis during his growth inside mom, because, just like with the testes, we’d expect the development of that penis to be driven by the presence of a Y chromosome.
Except that’s not the case!
During an embryo’s growth, the default development for the rather off-putting scientific term, our external genitalia, is female - labia, clitoris and a few other, less interesting bits and pieces.
But the switch that causes these to develop instead into a penis isn’t the chromosomal one we saw earlier but this time, a hormonal one, testosterone to be specific.
Testosterone has to be circulating through a male embryo during its life and development in the uterus if a penis is going to form. And whilst an XY male embryo usually produces enough of this hormone to get both a penis and testes, it’s not a given!
Similarly, it’s possible for female embryos to have ovaries because of their two X chromosomes making up their 23rd pair, but a penis because of lots of testosterone during their development.
These types of mismatch are part of a category called disorders of sex differentiation (DSD) and whilst no one would call these disorders common, approximately 1 in 5500 children will be born with one of these DSD conditions - not quite as rare as we might’ve thought?
Hopefully, having continued to read this blog up to here (and I greatly appreciate it), we can see there’s a lot tied up in the use of the terms male and female - we’re assuming a match between the sex chromosomes, the hormones produced and the presence or not of a penis.
Phew!
But whereas, sex is relatively measurable and quantifiable, our gender is most definitely not.
I started this post talking about what I’m not qualified to discuss, and I’m going to finish by mentioning a scientist who absolutely does know what she’s talking about when it comes to gender.
I enthusiastically encourage everyone to put the kettle on and then sit down with a cuppa and read Krista Conger’s article “How sex and gender which are not the same thing influence our health”. She writes so clearly, describing the many factors that go into building our gender and discussing how our gender affects almost every aspect of our lives including, amazingly, our chances of recovering from major health issues such as a heart attack, completely fascinating!
https://stanmed.stanford.edu/2017spring/how-sex-and-gender-which-are-not-the-same-thing-influence-our-health.html
