Natural History Museum - scientists please!

[PenguindreamsofDraco]

I was there yesterday and wandered into the human biology section. Lots of sex, no gender, all good. Then I got to the bit on hormones and here I got confused.

It showed how XX and XY are the chromosomes and the baby gets one from each parent. There was a big pictorial flowchart on the wall showing how the genital ridge is formed a few weeks after conception. Then it said that at this point an XX genital ridge can turn into penis/testes and the XY genital ridge can turn into vulva etc.

It said if there were male sex hormones then the XX (or the XY)embryo would develop male characteristics and if there were no male sex hormones then the XX (or the XY) embryo would have female characteristics.

Scientists, what is this on about? The way the wall chart read (and it was covering an entire wall), irrespective of your chromosomes you could end up 'male' or 'female', it just depends on whether there are male sex hormones swilling around.

Are there really that many XX people wandering around with penises and testes? It honestly read to me from the wall as though it's pretty much 50/50 i.e. it's not your chromosomes that matter but the 'male sex hormones'.

Can someone explain this? My fear was that something very very rare is being presented as fairly common place, and I did rather wonder why that might be.

Thanks!

There are XY individuals who are women: they have Complete Androgen Insensitivity Syndrome.
To be a man, AIUI, you have to have a fully functional Y chromosome, so if it's not working, it generally means female external genitalia.
My biology degree is quite a while ago though so I've mainly got this from recent reading around the topic.

(And yes it's rare, but the principle is fairly simple, Y= male, no Y or v rare broken Y = female)

Also a scientist and what the NHM have on their display is correct. The only caveat is I think ovary development is dependent on additional pathways. Otherwise, yes, the development of external genitalia (inc the vagina) is driven by hormones. Female is the default in the absence of testosterone.

Did it say in the exhibit that this is vanishingly rare? Because if not, then you are right and it us misleading in the extreme.

It sounds like a way to justify the foetal wash trans explanation, to reduce the importance of chromosomes.

It’s misleading. The ‘default female’ thing isn’t really correct. It’s more that the Male structure requires one set of specific inputs and the correct female another. Embryos don’t start out female then turn male depending on the amount of hormones washing around. They’re conflating absence of defined Male structures and presence of female characteristics with actually being female.

Before this whole trans thing I’d have shrugged and thought it was too nuanced an argument to point out. But as the TRAs are misinterpreting it to imply sex is environment dependent then I can see why it pissed you off.

You had structures like gill precursors as an embryo too - but you’re not a fish.

I'm also interested in the OP's question:

Are there really that many XX people wandering around with penises and testes?

From what's written above the answer sounds like "no". Or would it be one of those things where the developmental pathways are so complex that in a large enough population, billions, you can end up with very unusual, but extraordinarily rare, developments?

It def happens, there's a famous model, but this makes it sound like it's ALL about hormones, which is a major trans narrative. Despite the fact there's nothing intersex about trans people, and most transwomen have had completely normal male physical development.

person now known to be male with cais

That particular exhibition is really dated, I remember it being the exact same 20 years ago!

Charlie but she doesn't say she's male, she was brought up female and, it looks like, assumed to be female at birth but then found to have a disorder of sexual development i.e. intersex disorder.

So I'd say she's a woman with an intersex disorder, and as the amazing @mrkhtake2 says, people with intersex conditions generally want to be left alone to be men or women who have an intersex condition, not told they are different to how they are.

Thanks. No, it very much did not say it was vanishingly rare. It gave the impression that it was pretty much 50/50 if you with your XX chromosomes ended up a man or a woman.

But if it is misleading but dated, I am prepared to shrug and ignore. Misleading and recent, and frankly my radar is set to cynic at the moment.

I totally agree with you, I was only saying male because we have been technical and it was to explain. I totally agree - sometimes it feels like intersex people are denied any agency at all in this debate.

That was to drsproyse

Don't forget, development is driven by the actions of hormones on the sexed cells.
Its not that the default human is female, the default fetus is a fetus.
A male fetus cannot develop female sex organs which include a clitoris no matter how many female hormones it is exposed to.

this makes it sound like it's ALL about hormones, which is a major trans narrative. Despite the fact there's nothing intersex about trans people, and most transwomen have had completely normal male physical development.

This is what I find especially annoying - they use 'intersex' conditions as if they prove trans is 'true', despite the fact that no transwomen/men ever claim that they were born with an 'intersex' condition.

There are some heavy implications going on though - most people have heard that there are a few babies that cannot be determined, and when TRAs tell you that they were "always a girl/woman" then they are heavily implying that the midwife got it wrong.

I don't think it's correct to say that there are people with XY sex chromosomes who ARE female. I think it is more correct to say that a very small percentage of people who are genetically male (XY sex chromosomes) appear female or have ambiguous genitalia. They have intersex conditions, also known as disorders of sex development.

charleston I do think you need to defer to individuals who have those intersex conditions though.
It's not up to me to say that a woman with CAIS appears female if she's been raised as a girl and always thought she was a girl/woman until she found out she was unable to bear children or produce ova.
Yes, she has a DSD, rendering her infertile.

But I am pretty sure people like @ClairCAIS on Twitter do not say they are male but identify as female, nor that their sex is "intersex". They say that they are female.

CAIS effects between 2 to 5 people per 100,000 so extremely rare.

Indeed it is extremely rare and frankly not massively relevant to the trans discussion (except where TRAs try to weaponise it).
But not my place as someone without a DSD to tell someone who has one, what to call themselves (same with other medical conditions).

Why would the NHM, which in this room is dealing with a fairly simplistic version of everything human biology related, be putting something up on the wall which (if I'm understanding you all correctly) can only be 'right', if it is right at all, in a minuscule number of people?

And yes, it does read as though it's all about hormones - it was the presence or absence of the 'male sex hormone' which determined sex, was what I (an intelligent, GC but not scientifically-minded person) took away from it.

Hi, I studied a biology subject fairly recently and the sex chromosomes vs development was what was used in one of my lectures to demonstrate genotype vs phenotype. No mention of gender. Discussion of intersex and chromosomal disorders and hormonal problems. The lecturer said she chose it because it's simpler and better understood than things like hair colour ; )

Anyone watch the Christmas Lectures this year? There was one section where the presenter was asked to describe a hidden guest based on their genome.

The first thing she said was ‘It’s a woman’.