At the London 2012 Olympics Opening Ceremony, Caster Semenya had the honor of carrying South Africa’s flag. This week, she makes her Olympic debut (qualifier preliminary heat spoiler alert) representing her country in the 800m and 1500m events. This is in stark contrast to 3 years ago, when Semenya was banned from competition by the IAAF after cruising her way to gold in the 800m at the World Athletic Championships in Berlin. Combined with her physical appearance, Semenya’s dominating performance came at a price, fueling speculations that she was not, in fact, a woman. After her victory, Semenya was barred from competing until her gender was verified by genetic testing. As you will see, this can be subjective and unreliable (You can try for yourself using the HHMI’s biointeractive gender test).

Humans have two sex chromosomes designated as X and Y chromosomes. Females have two X chromosomes (XX) while males have one X and one Y chromosome (XY). One of the major factors that initiates male sex determination is a protein called Testis-determining factor, which is encoded by the SRY (Sex-determining region Y) gene normally found only on the Y chromosome. So, at first glance it would appear that a simple sex chromosome test would suffice to verify sex. 

In humans, females have two X chromosomes and males have one X and one Y chromosome. The Sex-determining region Y (SRY) gene drives male sex determination and is found on the Y chromosome.

However, the  line delineating sex is not so rigid– disorders of sex development (DSD) can complicate reconciling genetics with gender and sex. For instance, in Swyer syndrome, individuals appear outwardly female and have a normal uterus and Fallopian tubes, despite having the  male sex chromosome karyotype (number and appearance of chromosomes in the cell): XY. This condition arises when the SRY gene on the Y chromosome has either been lost or mutated and, as a result, male sex determination cannot be initiated. Instead, these individuals develop physically as females. 

Male sex determination cannot be initiated because the SRY gene is either mutated or lost.

On the other hand, an individual with an XX karyotype can develop as male is if one of the X (X*) chromosomes abnormally carries the SRY gene. The SRY gene can find its way from the Y to the X chromosome through chromosomal crossover, a phenomenon where corresponding chromosomes exchange parts with each other to generate new, unique chromosomes. This usually occurs during meiosis, a specialized form of cell division that gives rise to either sperm or egg. Crossovers ensure that different combinations of paternal genes are packaged into sperm and different combinations of maternal genes are packaged into eggs. This recombination of chromosomes is the reason why we look different from our siblings (exception: identical twins) and is generally good because it increases genetic diversity.

Recombination between the X and Y chromosomes normally occurs only at the tips of the chromosomes, beyond the region that encompasses the SRY gene. However, sometimes recombination can go awry and crossing over occurs such that the SRY gene is moved to the X chromosome. Since the SRY gene is located on the Y chromosome, the abnormal recombination event that results in an X* chromosome must occur in the father of an XX individual. The presence of the SRY gene, even in the absence of a Y chromosome, is sufficient to initiate male sex determination.

Abnormal recombination in the father of XX males, results in an X chromosome that carries the SRY gene (designated X*). Reproduction involving sperm that carry the X* results in XX* males since the presence of the SRY gene, even in the absence of a Y chromosome, can initiate male sex determination.

Given the importance of the SRY gene in male sex determination, one might expect a test that detected the presence of SRY would be adequate to verify gender. But even this test has it’s problems. For one, the test is subject to false positives since it can detect the presence of a mutated, non-functional SRY gene. There are also conditions which can override male development, even when the SRY gene is present. Such was the case for “8 of 3,387 female athletes” who tested positive for the SRY gene, but were allowed to compete at the 1996 Atlanta Olympics. In addition to carrying SRY, these 8 athletes also had a condition known as androgen insensitivity syndrome (AIS), which rendered them insensitive to the effects of male hormones such as testosterone.

Now, the International Olympics Committee (IOC) is pivoting away from gender verification to what they consider testing female “eligibility” by measuring levels of naturally occurring testosterone, a hormone classically associated with masculinity. This is not to be confused with tests that detect synthetic testosterone used for dopingUnder the IOC’s new rules, “women with levels of testosterone that reach a man’s [emphasis mine] normal level will be barred from competing with other women if it is found that the athlete’s body is responsive to androgens.” Still sounds like a gender verification test to me.


Unfortunately, testosterone is also an unreliable standard. For one, some women have abnormally high levels of testosterone, a condition known as hyperandrogenism. Secondly, as Rebeeca Jordan-Young and Katrina Karkazis write in the New York Times, “Testosterone is one of the most slippery markers that sports authorities have come up with yet. Yes, average testosterone levels are markedly different for men and women. But levels vary widely depending on time of day, time of life, social status and — crucially — one’s history of athletic training. Moreover, cellular responses range so widely that testosterone level alone is meaningless.” It’s also unclear whether higher levels of testosterone is a key factor in athleticism in women. Lastly, androgen insensitivity syndrome (AIS), or the inability to respond to male hormones such as testosterone, is overrepresented in women athletes. 

Testosterone testing, and gender verification in general, also reeks of sexism and discrimination, reinforcing not only perceptions of what a women should look like but also placing limits on what women can physically achieve**. Jesse Ellison of the Daily Beast writes,

“It all highlights a cruel injustice: the policy—and the testing, treatment, and humiliation that can come with it—only applies to female athletes. Men who excel at, say, ice dancing or synchronized swimming, where success has more to do with grace and rhythm than brute strength or speed, simply aren’t questioned in the same way women are. In 2010, after two French-Canadian sports commentators snickered over the flamboyant skating champion Johnny Weir and suggested that he should compete with the women, they were immediately and vociferously condemned for what was widely perceived as homophobic, despicable language. (This was, keep in mind, precisely the moment that Semenya was living in virtual exile after the subject of her gender had made international news.) Similarly, there is no upper—or lower, for that matter—limit to the amount of testosterone their bodies naturally produce.”

All of which raises the question: If the IOC feels that high levels of natural testosterone offer an unfair advantage, then will they apply an eligibility policy to men as well?

China’s Ye Shiwen after winning gold in the women’s 200 IM.
Photo by Adam Pretty/Getty Images

Note: On the use of gender, Wood and Stanton: “Unfortunately, ‘gender verification’ is a misnomer that confuses the distinction between sex and gender. Sex is a biologic definition that distinguishes male and female; gender is the sense of one’s own self as a man or woman.”

** While the speculations surrounding Chinese Olympic swimmer, Ye Shiwen, is the suspicion of doping and not gender, it should be noted that it has been framed within the context of gender since in the “final 50 meters of the IM’s freestyle leg, she swam faster than Ryan Lochte did in that portion of his gold-medal-winning 400-meter IM.”

1) Eggers S, Sinclair A. Mammalian sex determination—insights from humans and mice. Chromosome Res. 2012 Jan;20(1):215-38. Review. PubMed PMID: 22290220; PubMed Central PMCID: PMC3279640.

2) Wood RI, Stanton SJ. Testosterone and sport: current perspectives. Horm Behav.2012 Jan;61(1):147-55. Epub 2011 Oct 1. Review. PubMed PMID: 21983229; PubMed Central PMCID: PMC3264812.

Related Reading:

Olympic inequality: Studies show Olympics commentary differs based on gender, race and nationality

Sex Hormones! The Chemistry Behind Testosterone Doping


by Viet Le

5 thoughts on “The problem with gender verification in the Olympics.

  1. Another potential you could add to the list: There could be an intersex individual, who is, perhaps, chromosomally XY, but had ‘in between’ genitals at birth, and was surgically reassigned female by their pediatrician.

    1. Stella Walsh (Stanisława Walasiewicz) was a Polish athlete that won Olympic Gold (1932) and Silver (1936) in track. An autopsy after her death revealed that she had “ambiguous” genitalia–it turned out she was a mosaic: some of her cells were XX and some were XY. Ewa Kłobukowska, another Polish athlete, won Gold and Bronze at the 1964 Olympic games in Tokyo. She failed a gender verification test, but it was later revealed that she was also a genetic mosaic, except her cells were either XX and XXY. I’ve read that her testes were removed and she was being treated with estrogen–but I can’t find a reference for that.

      Ritchie R, Reynard J, Lewis T. Intersex and the Olympic Games. J R Soc Med. 2008 Aug;101(8):395-9. PubMed PMID: 18687862; PubMed Central PMCID: PMC2500237.

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