The Baffling Biology Behind the Olympic Games

Female athletes are being barred from sports on the basis of their biology — but is it justified?
Jenn Halweil
Olympics sign
Olympics sign


In the 1960s, sisters Irina and Tamara Press were summoned to stand naked in front of onlookers for an inspection.

The sisters were forces of nature in the track world. Together, they broke over twenty five world records and won half a dozen Olympic gold medals. Tamara was a thrower, competing in shot put and discus throw. Irina was a sprinter, competing in the 80m hurdles, 4x100m relay, and more. The duo was unstoppable.

That is, until the European athletics championships introduced the “nude parade”— an external genitalia examination to verify that athletes were female. Over the course of the nude parade’s run, over 243 female athletes were examined by a committee, who would determine if they had any “abnormalities.” Irina and Tamara declined to show up and both retired from international competition.

The Olympics, and sports as a whole, have a shaky history with biology. From inhumane sex testing in the past to questionable disqualifications today, what motivates the Olympic Committee? Let’s explore the baffling biology behind gender and the games.

The human body typically has 46 chromosomes, neatly paired up into 23 groups. These chromosomes are made up of tightly-coiled DNA. The first 22 pairs are called the autosomes, and the last pair are called the sex chromosomes.

But back up a minute.

The term “sex chromosome” isn’t all that accurate for describing that last pair. In fact, the actual “sex determination” — that is, whether individuals are considered biologically female or male — is controlled by an incredibly small portion of the chromosomes. Most of the genetic material contributes to your features, functions, and more, just like any of the autosomes.

The sex chromosomes are simple: if you have a Y chromosome, then you’re male.

Hold on, though. There’s an issue with that. Biological females can have Y chromosomes too, and biological males can have two X’s. Some women have male cells in their bodies, and some males have female cells in their bodies. What we’re encountering changes a lot of our ideas about sex. Rather than sex being a binary female/male divide, biologists are increasingly looking at it as a spectrum.

As put by the Intersex Society of North America (ISNA); "Disorders in sex development", or DSDs, refer to when an individual has an atypcial chromosomal, genital, or anatomic development. The term intersex is very controversial; many see it as dehumanizing, while others embrace it wholeheartedly. In accordance with the ISNA, we will be referring to these conditions as DSDs for inclusion and simplicity. 

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DSDs are surprisingly common, with estimates of their frequency ranging from 1 in 100 births to 1 in 4,500 births, However, according to some researchers, almost everyone possess cells of a different biological sex, thanks to microchimaeraism. When someone gives birth, some of their genetic material is given to the child, while the fetus’s genetic material stays with the individual. As a result, some of the body’s cells contain different chromosomes than their assigned sex. In more general chimaerism, a person could have large portions of their body made up of cells of a different sex, which can sometimes impact their genitalia. Intersex characteristics occur when an individual has chromosomes or genitalia that don’t fit into our assigned binary sex.

There’s an important distinction to make here too: That sex and gender are not the same thing. While sex typically refers to the “biological” features, gender is built upon social ideas. This idea of gender being binary is a relatively new development, with many groups of Native Americans, Samoans, and Thai, and more recognizing more genders throughout their history.

In other words, there’s a lot of people that don’t fit into how society views sex — and this plays a big role in sports.

Just days ago, Namibian Olympic runner Christine Mboma was disqualified from the 400 m (1312 ft) race, her favored event. Mboma’s natural testosterone levels were reportedly too high to compete, although she was able to compete in the 200 m (656 ft), where she broke the under-20 world record in the event twice. Before Mboma’s controversy, Caster Semenya was disqualified in the 800 m (2624 ft) race due to her testosterone levels. Irina and Tamara Press, the sisters summoned for a nude parade, were believed by some to have some form of DSD. Many times, athletes aren’t even aware they have DSD or elevated hormone levels, Mboma included.

Testosterone is a hot topic in athleticism. Using exogenous (literally, originating from outside) testosterone, or testosterone that isn’t naturally formed in the body, is typically banned in sports, as it artificially increases athletic performance. Many also point to testosterone as being the reason why males typically excel in sport. As a result, female athletes with higher testosterone are typically barred from sports because it is believed to enhance their performance.

But there’s a problem with this basis: What we know about testosterone levels and female athletic performance is far from set in stone.

Most studies on how testosterone changes female athleticism look at exogenous testosterone, not the natural endogenous testosterone. This is a key issue in these studies, as naturally-occurring testosterone can’t be compared to the exogenous form used in the studies. Additionally, higher levels of testosterone don’t always correlate with athletic performance; one investigation concluded that around 1 in 4 male athletes in the Olympics had levels of testosterone that were below the lower limit. Surprisingly, many of these athletes were competitors in strength and speed-oriented events such as weightlifting and running.

Some findings have even suggested that testosterone isn’t a major player in performance for males or females. The study, referred to as GH-2000, found that testosterone levels between sexes were remarkably similar, and rather the lean body mass (LBM) caused sex differences to arise.

The authors of “Intersex and the Olympic Games” sum it up nicely: There is “no evidence that female athletes with DSDs have displayed any sports-relevant physical attributes which have not been seen in biologically normal female athletes.”

Increasingly, scientists are turning away from testosterone being the sole indicator of athletic prowess, yet the International Olympic Committee is still dedicated to barring some individuals with naturally high levels of testosterone from competing.

At least, women with naturally high levels of testosterone.

Take Michael Phelps, the most decorated Olympic athlete of all time. Phelps’s body produces less lactic acid than the average person, thanks to a helpful genetic variation. This means that he needs less time to recover during physical activity, providing him with a biological advantage over his competitors. Meanwhile, if a woman has naturally inflated androgen levels, she’s booted from competition. In fact, male athletes have no upper natural physiological limit in the Olympics, though they are tested the same as women for doping.

As University of Cambridge’s Vanessa Heggie puts it in “Testing sex and gender in sports; reinventing, reimagining and reconstructing histories,”: “There are probably hundreds of genetic variations which lead to ‘unfair’ advantages in sport; only those associated with gender are used to exclude or disqualify athletes.”

The science is changing our view of sex. Sex isn’t binary. It may not even be a spectrum, but more like a golden ratio spiral with lots of different variations. So is it time the Olympic Committee let go of outdated sex testing?

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