This is the menstrual cycle.

Trans-identified males do not have one. This is the uterus, from which we bleed.

Trans-identified males do not have one.

People with 5ARD are male, not female

In defence of Semenya et al, many argue:
1. athletes with 5ARD are female;
2. features associated with 5ARD are normal female variation;
3. these athletes should be included in female sports.

The first claim is incoherent. To understand 5ARD, let's look at healthy reproductive development.

Both male and female development are well-understood.

“Sex screening in athletes is racist!”

Why? Really struggling with this.

In our recent paper (cited by World Athletics @sebcoe) calling for the reintroduction of sex screening in the female category, we make it very clear that this type of screening must be:

1. Cohort-wide | performed in all athletes wishing to enter the female category, regardless of skin colour, religion, nationality etc.

2. Early | to protect privacy and dignity, and avoid athletes being front-page news.

With these parameters in mind, the sex screen itself cannot be considered “racist”.

onlinelibrary.wiley.com/doi/epdf/10.11… Citing historic ethical issues won’t wash. We all acknowledge these. Early, cohort-wide screening will avoid the failures of the past.

So the cry of “racism” must be aimed elsewhere, presumably anchored on the premise that previous targeted screening (which is precisely what I and others advocate against) brought multiple black athletes and very few white athletes to our front pages.

In sport, we are interested in the effects of male or female development on the body, not the booty.

The category boundary between males and females is male-pattern androgenisation - having testes that make testosterone (T) and a functional T response. Disorders of sex development (DSDs) affect reproductive development, and sometimes challenge legal and social sex classification.

5ARD, for example, means a male baby doesn't make the hormone required for penis development. The baby may be misclassified as female at birth.

On “we all start as females” (by request).

At the level of anatomy, “female” describes a particular reproductive system - eggs in ovaries, oviducts, uterus, cervix, vagina and vulva. This reproductive system begins to differentiate at around six weeks post-fertilisation, when the embryonic gonads - two balls of cells clumped in your pelvic area - turn into ovaries and not testes.

I ran a fairly straightforward analysis of track and field performances across junior ages in different track and field competitions.

The raw analysis looks like this for international records. Above the line is male advantage, below the line is female advantage.

This pattern its repeated across national and state-level competitions. You can see that for almost all events at all ages, boys hold advantage over girls.
Where female advantage is detected, this is easily explained.

At 10 years old, girls grow ahead of boys, and catch up/overtake them briefly in running.

The female advantage in discus at 15-16 years old is because girls throw lighter implements.

The distance drop off as boys move to the 2 kg discus is obvious.

Hello @michaelshermer

Please see the following links to various papers and commentaries I and others have published on sports categories.

Please follow me (obvs 😂), @TLexercise @Scienceofsport @runthinkwrite @cathydevine56 @BrowngaGreg @MaryOConnorMD @DrMJoyner and associated scientists for academic work.

Guys, add your papers below please. Where it all started (academically): “the muscular advantage enjoyed by transgender women is only minimally reduced when testosterone is suppressed.”

There are a couple of letter responses linked to this too.

link.springer.com/article/10.100…

Let’s have a think what hormone categories looks like. And let’s assume that @neiltyson is considering a high/low T category. This has also been proposed by @AliceDreger

Thanks for the shoutout, Colin @SwipeWright

https://twitter.com/swipewright/status/1865631106252382617

The proposal only works if you don’t deny evolution and sexual selection. Remarkably, there are academics who argue there is no biological basis for why males run faster than females. While it is plausible ongoing underinvestment in female sport means female athletes have not yet reached their full potential, it is frankly ridiculous to think this can explain the entirety of the performance gap.

See Sheree Bekker et al for more details on why, because one time, this one female figure skater won a medal, Usain Bolt should be allowed to race against females.

Why male advantage in sport is not a social construct: height.

Height is a key difference between males and females. What is nature v nurture? What does that mean for sport? Bigger skeletons are most obviously driven by longer bone growth. Key bones like those in your thigh (“long bones”) grow from their end to get longer, making you taller.

Ok, my charity wears off.

Bekker’s presentation of the “Hilton and Lundberg” argument is nonsense.

At no point have either of us, or anyone else we work with, reduced male advantage to simply muscle mass/strength. @TLexercise @Scienceofsport

https://twitter.com/fondofbeetles/status/1855924222385643872

In the contrary, we have consistently argued that male advantage stems from many physical then functional outcomes of male development.

We spent hours (actually days 😂) creating this graphic, trying to highlight key areas of physicality that underpin male advantage.

HowTF is this reduced to “it’s all muscle”?

I’m going to put my charitable hat on, and try to elucidate - maybe even, as good practice, steelman - an opposition argument.

Specifically, this one:

https://twitter.com/bjsm_bmj/status/1854863486129476058

Let’s set a concrete example: the 10 second barrier (100m sprint).

Wiki - allowing for small errors - tells me that around 200 male sprinters have broken it. We know, of course, that no female sprinter has been close (Flo Jo record 10.49s).

As the latest on Olympic boxer Imane Khelif is reported, a diagnosis of 5ARD is almost certain. I and others first raised the likelihood of this DSD a few months ago.

Understanding how the developmental biology of DSDs interacts with sports categorisation is crucial. I spoke about this with Andrew Gold during the competition:

In August, we were invited by the Scandinavian Journal of Medicine & Science in Sports @WileyGlobal to make an argument for screening for eligibility into the female category.

We proposed a cheek swab screen of DNA, performed before an athlete is thrust into the spotlight, with follow up care in the case of unexpected results. @WileyGlobal This month, two responses to this editorial have been published side-by-side.

The first was an argument against our proposal:
onlinelibrary.wiley.com/doi/full/10.11…

Ricin is extremely bad for people.

So bad, it’s a viable way to way to wipe out populations.

So bad, it’s regulated at the same level of weapon as sarin and mustard gas.

So bad, the ricin lab at my alma mater was more heavily-regulated than the HIV (live, infectious) lab. Anyone found with some home stash of ricin has no defence.

It comes from castor beans (common enough). But you don’t accidentally grind them up and extract the toxin as a kitchen experiment.

“Sex allocation” is a term used to describe how the two sexes - male and female, binary - are distributed within a species.

Humans are gonochorists. This means that the two sexes are divided between two classes of individual, with each class specialised for either the male or female reproductive role. In fact, almost all animals are gonochorists. It is a remarkably stable evolutionary strategy, given that all individual resources can be directed into one role, rather than split - and perhaps compromised - by division across both roles.

It is not better to be a jack of all trades but master of none…

Lots of genuine people asking questions and less genuine people building hilarious strawmen about sex screening in sport.

Another thread, on SCREENING. Sex categories in sport are built around sex, which is anchored in your gonads.

Sports federations that have grasped this issue are equally clear that categories are concerned with physical development that starts with gonads.

OK, science geeks. Sex testing and sport.

There are many people spreading misinformation about the reliability of sex testing, repeating arguments made for its abolition some 25 years ago.

I don’t know if they have noticed that we’ve undergone something of a genetics revolution over the past few decades 😀 So let’s look at some chromosomes.

Historically, chromosomes were analysed by adding a chemical dye to cells and looking at their shape and size. Given that most animals have two copies of each chromosome, the pairs could be lined up by matching their shape and size.

These are chromosomes stained with a dye called hemotoxylin. I still use this dye in the lab today.

I blocked Dope because he could not entertain a discussion that wasn’t on his terms within his framework.

I don’t accept his framework. And because he wouldn’t discuss a single thing within mine, it was pointless. Because he wouldn’t discuss anything outside of his own narrow ideology, I am left with no idea whether he even understands that my framework is different to his.

His repeated questions indicate he seems to think they were natural progressions of my framework.

They were not.

Let’s examine this list of “tranimals”.

Trigger warning: includes clownfish.

https://twitter.com/PeterTatchell/status/1776950643141361869

Clownfish. Some dominant males can change their biological sex to female. We know they have switched sex because they change their gonad tissue, stop making sperm and start making eggs.

Two sexes? Yes.
Sex change? Yes.
Trans Nemo? He’s way down the pecking order of “dominant male”. Doubtful clownfish have gender identities.

Here, we argue:

1. We disagree with the assertion that the IOC framework [fairness, inclusion, and nondiscrimination on the basis of gender identity and sex variations] is consistent with existing scientific/medical evidence and question its recommendations for implementation.

https://twitter.com/FondOfBeetles/status/1770767523421499452

2. Testosterone exposure in male development:
--> physical differences between male and female bodies
--> male athletic advantage in muscle mass, strength and power, and endurance and aerobic capacity.

The IOC's “no presumption of advantage” principle disregards this reality.

You know that story about breast milk from a man being as good - BETTER - than that from a woman?

telegraph.co.uk/news/2024/02/1… You know it, the one informing policy in at least one NHS trust?

thetimes.co.uk/article/transg…