After completing these two case studies, consider the two questions you were asked at the start of the interactive.
So is there a test that can determine an individual's biological sex?
And can testosterone produced by an athlete's own body provide an "unfair" advantage?
Sex Versus Gender
You may have realized that there isn't a single test that can determine an individual's biological sex in all cases. Like most human traits, biological sex is variable and influenced by a variety of genetic and environmental factors. In addition, an individual's concept of themselves, or their gender identity, may or may not match their biological sex.
What About Testosterone?
Starting in 2000 eligibility guidelines for women's events have focused on athletic performance rather than biological sex, using testosterone as a marker of men's competitive advantage. But the science on testosterone is far from settled.
In 2015, sports officials temporarily stopped measuring endogenous testosterone levels in cisgender female athletes (following Dutee Chand's challenge) for lack of evidence that higher testosterone levels provide more of an advantage than other biological differences. Guidelines for transgender female athletes state that they can only compete in women's events if they maintain testosterone levels below 10 nmol/L for at least a year prior to competing.
In 2018, the testosterone rules were updated following a study that showed an advantage in certain track and field events for female athletes who have higher testosterone levels. According to the new rule, athletes with endogenous testosterone levels greater than 5 nmol/L and who are androgen-sensitive (meaning that their bodies respond to testosterone), cannot compete in women's track events from 400m to the mile. Several scientists have disputed the study's results.
Biological sex is defined by an individual's combination of chromosomes, hormone levels, internal and external reproductive anatomy, and sex characteristics. It is usually treated as a binary trait: female or male. Biological sex is different from gender, which is based on social and cultural ideas of what it means to be a woman or man. Gender identity refers to an individual's concept of who they are. Gender identity does not always match biological sex.
Gender identity refers to an individual's concept of themselves, which may or may not match their biological sex.
An individual whose biological sex assigned at birth was female and identifies as a woman.
An umbrella term for all genders other than woman and man.
An individual whose biological sex assigned at birth was male and identifies as a man.
An individual whose biological sex assigned at birth was male and identifies as a woman.
An individual whose biological sex assigned at birth was female and identifies as a man.
An endogenous substance is one that originates or is produced within the body. On the other hand, an exogenous substance comes from outside the body. Researchers who measure athletes' testosterone levels can determine if the hormone is exogenously or endogenously produced.
10 nmol (nanomoles) per liter
A mole is an amount of a substance, specifically 6.022 x 1023 atoms of that substance. 10 nanomoles per liter is equivalent to one hundred-millionths of a mole, or 6.022 x 1015 atoms, in a liter of fluid. This measurement was chosen as a cut-off for participating in women's events because most female athletes have values well below 10 nmol/L. More recent guidelines have imposed a cutoff of 5 nmol/L in certain events.
The study was published in the British Journal of Sports Medicine (Bermon S, Garnier P. Br J Sports Med 2017;51:1309-1314). The authors separated elite female track and field athletes into three groups according to their testosterone levels and then compared their performances in various events. They concluded that athletes in the group with the highest testosterone levels performed better compared to those in the group with the lowest testosterone levels, but only in five events: hammer throw (4.53% advantage), pole vault (2.94% advantage), 400-m race (2.73% advantage), 400-m hurdles (2.78% advantage), and 800-m race (1.78% advantage). The new testosterone guidelines do not apply to the hammer throw and pole vault events, but apply to races and hurdles.
Several scientists have argued that the study by Bermon and Garnier did not provide sufficient scientific evidence of a causal relationship between increased endogenous testosterone and increased athletic performance. (Menier, A. British Journal of Sports Medicine 2018; Sőnksen PH et al., British Journal of Sports Medicine 2018.)