Bringing evidence back to trans inclusion in sports

Pre-registered hypotheses about trans women in sport, common claims, and criteria for invalidating these through evidence.

Mallory Moore
5 min readFeb 6, 2023


There’s a huge amount of debate about trans women’s inclusion in women’s sports. While it’s common for trans women to be accused of being detached from material reality, the best of the opposition to trans women’s inclusion this is based on testable hypotheses. It doesn’t matter whether you hold our attachment to reality in contempt — the evidence will prove who is right whatever either of us would prefer.

So, here are some clear cut assertions, set as challenges to be falsified, in the spirit of Hawking’s bet against time travel, or James Randi’s challenges to psychics and paranormalists, or the RSA factoring challenges.

I’ll set some challenges. I’ll set some rules. I will try to make them as reasonable and fair as possible. If people who are skeptical of trans inclusion find the conditions unfair, I’m open to issuing amended versions of the challenges — especially if there is a suggestion that I have embedded “something up my sleeve” in the way the conditions are set, but I will strive to make the challenges as open to being defeated in the spirit of finding truth as possible.

Like all good sporting endeavours, these challenges are set in the recognition that the competition is only satisfying so far as both sides feel like they have a fair opportunity to win. But they are set so that participants in the challenge pre-agree to the rules when attempting to conclusively defeat the reasonability of trans women’s inclusion in sport.

I will say up front, as a gender abolitionist, I do not want to take unchallenged the binary oppositional sexism embedded in much of these debates or the general contempt and reinscription of patriarchal gender norms through the implied degradation of women’s athleticism (for instance the regular disfavorable comparison of cisgender women to “mediocre men” just stinks of contempt for women’s athletic feats). My personal views are that we need better models for inclusive competition beyond simple sex segregation. This is especially pressing in light of controversies around where intersex athletes fit into oppositionally sexist segregation that exclude consideration for variations of sex characteristics, and for the wellbeing and inclusion of nonbinary people who may not happily identify as men or women (despite those categories being the only offered in many cases).


Claim 1: Trans women have an unfair advantage over cisgender women

Advantage is not necessarily defined so that any individual trans women will be advantaged over all cis women. Even the weakest meaningful definition of advantage over cisgender women however requires, at minimum, at least some trans women will generally be able to beat the best trained cisgender women in a given sport.

Some sports obviously favour shorter, smaller bodies so this does not cover all sporting events, but a considerable number of sex segregated sports all the same.

For this reason:

Challenge 1: While no transgender woman has beaten the best woman in a given sport, there strictly can not be said to be an advantage of trans women generally over cisgender women.

As a simple rationality check of this challenge, in for instance the London marathon, hundreds of amateur male runners beat the fastest women every year.

If this challenge is defeated, it may be at least possible that trans women could have an advantage over cisgender women.

Claim 2: The UK Athletics ruling that trans women should be required to compete in an “Open” category does not meaningfully constitute a ban or discrimination.

UK Athletics have issued new policy saying they intend to replace current categories with a women’s category and an open category. The reason the women’s category exists is because for many sports, if it did not, women would not be competitive at all owing to being forced behind hundreds of male competitors.

Challenge 2: Transgender women are 1 in 200 people assigned male at birth. While the top thousand athletes in any category dominated by those assigned male at birth contains NO trans women, trans women have been excluded.

This condition of exclusion will be partially disproven by trans women constituting a any of the top thousand open-category athletes in any sufficiently popular sport, and completely disproven by trans women constituting a proportionate number of the top thousand open-category athletes.

If this challenge is overturned it may be arguable either way, but until then, it is objectively reasonable to claim that trans women have been banned in so much as that differential in performance will result in trans women being unable to have a probabilistically justifiable chances of participating.


1. Localised proofs are valid

If you disprove one of these challenges to popular claims under certain conditions, that is valid for like conditions. Similar to “breaking N rounds of a cipher” where you have weakened the cipher from the recommended number of rounds, localised proofs are not a full refutation of the premise in a challenge, but can be considered evidence of having disproven a weakened version of the challenge. This rule hopefully helps to allow skeptics to develop indicative evidence towards refutation in pieces where necessary.

2. The Apples to Apples rule

I have not specified what a “trans woman” is or proposed a specific degree of transition where it is fair to include trans women in women’s sporting competitions. Instead this is covered by an Apples to Apples rule: If you want to discredit competition under a certain standard, your evidence needs to reflect athletes for whom that standard applies, competing under the relevant conditions. That is to say: No bullshit, sports performance is measured by winning, not bone density or blood count or some other variable you want to use as a proxy for performance. Data from people actively using PEDs can not be taken as relevant to discussions on athletes where PEDs are banned. Winning a college meet can’t be treated as equivalent to winning an Olympic final.

3. No niche or team sports

The scope for these challenges is set at any sport which is managed by UK Athletics or the Olympics. There are lots of other great fringe sports around the world, but the elitism of Olympic competition produces both large amounts of athletic participation (helping with statistical validity) and financial incentives and sponsorship for any capable athlete to excel. These also seem to be the sports that people want to ban trans inclusion from.

Team sports (basketball, rugby etc) are excluded from this owing to the impossibility of disambiguating collective performance from the individual. They’re valid, but this approach is not valid to discussing performance around them.

4. No abuse

I reserve the absolute right to disengage if you can’t stick to evidence. I love proving anti-trans activists wrong as much as anyone else, but I don’t have to put up with abuse from strangers over nothing.

As a subsection of this rule, I’m disallowing rationalisations form the “Mediocre Man” theory. I want to see evidence of trans women having an advantage, collectively, over cisgender women. The “mediocre man hypothesis” exists as an untestable way of conjuring up a just so narrative which explains away the fact that historically trans women have not been better at sports than the best cisgender women. Also it’s self-evident that if trans women are collectively “mediocre men”, that would suggest acknowledgement of trans women not having a collective objectively measurable advantage over cisgender women. Because this just waves away the actual evidence with a post-hoc rationalisation, I think it is important to dismiss it as a refusal to engage with the evidence rather than a testable hypothesis.

Good luck! Let’s do science.



Mallory Moore

Trying to develop a gender abolition worthy of the wider abolitionist feminism movement.