Do intersex women athletes have an edge over the field?


Despite the likelihood that women born with male and female sex characteristics are overrepresented in athletics, there's remarkably little research into what advantages the condition bestows. Richard A. Lovett reports.


South African runner and current 800-metre world champion Caster Semenya.
Warren Little / Getty Images

When athletes line up for the first round of the women’s 800-metre final at the Rio Olympics on 17 August, one face is likely to be the face of victory … and controversy.

South African Castor Semenya is clearly the dominant female 800-metre runner on the planet, but she’s also almost certainly intersex, meaning she has a combination of male and female characteristics that many believe give her an unfair advantage.

So – if she is intersex, does that really give her a leg up?

Semenya is probably not the only intersex runner at the Olympics. “I would estimate that there are between five and 10,” says Joanna Harper, an athletics official and medical physicist from Portland, Oregon in the US, who consults for the International Association of Athletics Federations and the International Olympic Committee on gender and sports.

And for whatever reason, many of these runners appear to be specialising in the 800. By the time the field is winnowed by two rounds of qualifying heats, Harper suggests that there might be so many intersex runners in the finals that it could be “an all-intersex podium”.

Scientifically, intersex is a term that refers to any of a number of conditions that blur the traditional distinction between male and female. The most common yield genital abnormalities, but those most relevant to sports produce people who appear to be female but have internal testes that, at puberty, begin producing testosterone.

Thanks to that testosterone, Harper says, “they can see a large performance advantage”.

The result is an athlete who looks female but may be able to outcompete non-intersex women, adds South African exercise physiologist Ross Tucker. That’s a problem, he says, because the whole purpose of dividing the sexes in athletics is to protect women from unfair competition: “Sex divisions serve the same purpose as weight divisions in boxing.

“They’re there to ensure that a factor that is significant for performance – size in boxing, biological sex for all sport – can be regulated, to some extent, for both fairness and safety.”

For years, athletics has dealt with this via gender tests, ranging from humiliating medical inspections to chromosome tests or blood tests for testosterone. There were even tests to determine whether or not these women’s bodies were able to use the testosterone they produced. Some intersex women are insensitive to male sex hormones (collectively called androgens) and testosterone bestows them no advantage.

But in July 2015, the Lausanne-based Court of Arbitration for Sport, in a case involving Indian sprinter Dutee Chand, ruled that such tests are inherently discriminatory and threw them out.

Last year a court ruled that testing Indian sprinter Dutee Chand, seen here after winning the women's 100 metres at the Federation Cup Senior National Athletics Championships in April, and other 'hyperandrogenic' athletes was discriminatory.
Virendra Singh Gosain / Hindustan Times / Getty Images

Under the old rules, androgen-sensitive intersex women with high testosterone levels who wanted to compete at the highest levels were required to either undergo surgery to remove their internal testes or take testosterone-blocking drugs.

The rules have since been canned, though Harper notes that the effect isn’t completely fair. “Those who had surgery were out of luck, but the women who chose medication could now return to their natural testosterone level.”

Harper is unabashed in her belief that the decision was wrongheaded. “Those women are now running very fast times,” she says, “notably faster than they were prior to July 2015.”

Semenya in particular, she says, is now having a banner year in which she may be poised to break a 33-year record once thought to be untouchable because it was probably based on Cold War era state-sanctioned doping.

That said, there are no scientific studies specifically addressing the advantages intersex athletes may experience. “It’s extraordinarily difficult to gather data,” says Harper.

In testimony before the Court of Arbitration for Sport in the Chand hearing, though, exercise physiologist and medical doctor Stéphane Bermon of the Monaco Institute of Sports Medicine testified that he had unpublished data showing that 0.71% of female athletes at the 2011 Daegu IAAF world championships were intersex, compared to 0.005% of the overall population.

While 0.71% doesn’t sound much, Harper notes that this means intersex women were overrepresented at that meet by a factor of 140.

To put that in perspective, she says, a number of studies have suggested that left-handed baseball players might have an advantage (the reasons have to do with the layout of the baseball diamond and the mechanics of the game).

In the general population, Harper notes, left-handers are a 10% minority. But in top-level baseball, about 30% of players are southpaws (or ambidextrous) – an overrepresentation by a factor of three. That, Harper says, “can be used as an indirect representation of the size of the advantage”.

And if an overrepresentation of lefties in baseball indicates an advantage to them, she says, a 140-fold overrepresentation of intersex athletes in the 2011 world championships “is fairly sizable – to put it mildly”.

In other results presented in the Chand case, Berman estimated that high levels of testosterone in intersex women could produce a 3% improvement in athletic performance.

That’s less than the 10% difference normally seen between male and female world records but enough to make a staggering 3.5 seconds difference in an 800-metre race normally decided by far smaller margins.

Not that anyone is accusing intersex athletes of doping. “You can argue it’s not Semenya’s fault,” Tucker says. “That is the crux of this debate.”

But, he notes, “The physiological advantage of biological sex, primarily influenced by testosterone, is the single largest genetic advantage for sport.”

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Richard A. Lovett is a Portland, Oregon-based science writer and science fiction author. He is a frequent contributor to COSMOS.