The story so far

The International Olympic Committee (IOC) recently announced that only “biological females” will be allowed to take part in the Olympic Games and other IOC events under the female category, whether individual or team-based, effectively banning transgender women from competing. It stated that eligibility will be determined on the basis of an SRY gene test that all athletes must undergo. The SRY gene, found on the Y chromosome, usually triggers the development of male characteristics. Essentially, the IOC said the test will be conducted once, and if the gene is not found, the athlete will be deemed a “biological female” and allowed to compete.

The IOC claimed the move would ensure a “level playing field” for female athletes by protecting “fairness, safety, and integrity in the female category,” and that it will come into effect for the LA Olympics in 2028. However, there has been widespread criticism of the IOC’s decision. For starters, it comes at a time when instances of discrimination against transgender people are rising globally. There are other considerations as well, including whether SRY gene testing is the right way to determine whether someone is a “biological female”, the issue of individuals with intersex traits and whether or not trans women actually have an ‘advantage’ over cisgender female athletes.

What exactly did the IOC say?

The IOC said that according to scientific evidence, the presence of the SRY gene is an accurate marker of whether “an athlete has experienced male sex development.”

If an athlete is found to be negative for the SRY gene, they are eligible to participate in IOC events in the female category permanently, unless there is reason to believe the result was a false negative. What such a reason might be, the IOC does not specify.

There are exceptions too. Athletes diagnosed with Complete Androgen Insensitivity Syndrome (CAIS) or other rare differences/disorders of sex development (DSDs) “who do not benefit from the anabolic and/or performance-enhancing effects of testosterone” may be eligible to participate in the female category.

History of sex determination in sport

Sex verification tests have historically been controversial and, more often than not, humiliating for athletes. From the early practice of nude parades, in which experts examined athletes’ genitals, to later “scientific” sex verification tests, sometimes conducted without consent, sporting organisations have a chequered history of policing athletes competing in female categories.

Take, for instance, the case of Tamil Nadu’s Santhi Soundararajan, who hails from a marginalised community in Pudukottai. After her win at the 2006 Asian Games, Ms. Santhi was compelled to undergo a sex verification test – basically, a chromosome test, besides a physical examination – amid suspicions that “she is not a woman.” She was subsequently stripped of her medal and faced public humiliation. Ms. Santhi is reported to have an intersex trait, hypoandrogenism, wherein her body produces elevated levels of male hormones.

South Africa’s Caster Semenya is another example. The International Association of Athletics Federations (IAAF) required her to undergo a sex verification test after her gold in the World Championships 2009, and she was banned from competing. But following widespread criticism, the testing policy was changed to focus on testosterone levels instead.

The bottom line is that sex verification tests have long faced issues of accuracy. Even though the IOC claims that SRY gene testing produces accurate results, critics argue that misdiagnoses are possible. Jenny Graves, distinguished professor of genetics, La Trobe University, Melbourne, writing in The Conversation, notes “the SRY gene activates a network of dozens of genes that promote testis development or block ovary formation. Variation in any of these genes can produce girls with SRY or boys with no SRY.” For instance, there may be women with an inactive form of the SRY gene, which does not lead to the development of male sex characteristics.

People with intersex traits

People with intersex traits may have a combination of male and female biological characteristics. There are several variations of traits, and these can differ widely in degree too.

In the context of sport, what is relevant is the androgen insensitivity syndrome (AIS), which the IOC references in its policy. Androgens are hormones typically associated with male development, such as testosterone. Some individuals who are genetically male may be partially or completely insensitive to these hormones, resulting in typically female external sex characteristics. They may not, therefore, derive a lot of advantage – for instance, muscle growth – from the presence of androgens.

There is a widespread belief that testosterone contributes to the perceived physical advantages of transgender women – or people with diverse sex characteristics – over cisgender female athletes. According to the IOC, individuals with complete androgen insensitivity syndrome may be eligible to compete in the female category because they do not respond to androgens like testosterone. However, the Committee does not specify how this will be determined. It also does not clarify the status of athletes with partial androgen insensitivity.

Similarly, under the IOC’s new rules, individuals with intersex conditions such as 5-alpha-reductase deficiency and mosaicism may also be excluded from competing in the female category.

Do trans women have a higher advantage?

The idea of banning transgender women from competing in the female category is based on the assumption that, on average, men – because of the Y chromosome and testosterone – are stronger or superior to women in sports. But how much of the process of transitioning is considered when making this assumption?

On average, males are larger and stronger than females. Research also shows that there are roughly 20,000 genes not located on the Y chromosome, and these genes are shared by both males and females. Nearly one-third of these genes function differently in men and women, suggesting that differences between the sexes are not solely due to testosterone. Ari Berkowitz, director, cellular & behavioural neurobiology graduate program, University of Oklahoma, U.S., also writing in The Conversation, states that some basic physiological traits are influenced not by the SRY genes or hormones, but by the number of X chromosomes (which both men and women share). This is an important factor to consider.

When it comes to transgender women, hormone replacement therapy during transition increases oestrogen levels and suppresses testosterone. Assessing any athletic advantage requires considering when transition began and which sex differences have already developed. Some studies suggest that transgender women may retain, on average, longer limbs, stronger hand grip, and greater muscle mass. However, after two years of hormone therapy, their cardiovascular and respiratory function typically aligns with that of cisgender women.

The fact remains that current research is limited, and we do not fully understand the extent of any athletic advantage that trans women may have over cis women.