Transgender athletes: What do the scientists say?

Harper: Advantages are not necessarily unfair, and let me use two examples, one where the advantages aren’t unfair and one where they are.

Left-handed athletes have advantages over right-handed athletes in many sports. It is perhaps most marked in fencing where 40% of elite fencers are left-handed versus 10% of the population is left-handed.

But right-handed fencers and left-handed fencers can engage in meaningful competition despite the advantages that left-handed fencers have.

However, you never put a big boxer in the ring with a little boxer, no matter how good the little boxer is. No matter how hard the little boxer works, trains, how competitive they are, they can’t beat a big boxer. The size difference means there’s no such thing as meaningful competition between big boxers and little boxers.

So the question isn’t ‘do trans women have advantages?’ – but instead, ‘can trans women and women compete against one another in meaningful competition?’ Truthfully, the answer isn’t definitive yet.

Trans women can have disadvantages because their larger frames are now being powered by reduced muscle mass and reduced aerobic capacity, but that’s not as obvious as the advantages of simply being bigger.

Yes, it’s true that competition can often come down to a very small margin, but there are, in any competition, many factors that come into overall performance and just saying that ‘oh, somebody has an advantage’ in one factor doesn’t necessarily determine the outcome.

Tucker: When boys reach the age of 13-14, things start to change physically and we see increased muscle mass, bone density; [it] changes the shape of the skeleton, changes the heart and the lung, haemoglobin levels, and all of those things are significant contributors to performance.

Lowering the testosterone has some effect on those systems, but it’s not complete, and so for the most part, whatever the biological differences are that were created by testosterone persist even in the presence of testosterone reduction – or, if I put that differently, even after testosterone levels are lowered.

It leaves behind a significant portion of what gives males sporting performance advantages over females.