Why Defining ‘Female’ in Sports Is More Complex Than It Appears—and What That Means for the Transgender Athlete Debate

As sports governing bodies move to reinstate genetic sex testing, new research suggests that determining who qualifies as “female” in athletics is far more complex than commonly understood, raising significant implications for policies governing transgender athletes.

A recent analysis published by COYOTE Media Collective challenges the assumption that biological sex can be easily and definitively categorized for the purpose of competition. The article argues that the scientific foundation behind modern sex testing policies is far less settled than policymakers claim.

“The scientific evidence is very clear,” International Olympic Committee President Kirsty Coventry said in announcing the policy, but the COYOTE analysis directly disputes that assertion, concluding that “often it does not actually exist.”

Historically, attempts to define sex in sports have repeatedly failed to produce reliable or consistent results. Early efforts included invasive physical examinations, while later policies relied on chromosome testing introduced in the mid-20th century. Those tests, which screened for Y chromosomal material, were ultimately abandoned after decades of criticism from scientists, ethicists and athletes.

As the article notes, “lots of women have Y chromosomal material in their cells,” a finding that undermined the assumption that chromosomes alone could serve as a definitive marker of sex.

The persistence of these policies reflects a deeper issue: human biology does not conform neatly to binary categories. Individuals with differences of sex development, or DSD, may have variations in chromosomes, hormones or anatomy that do not align with traditional definitions of male or female. These variations are not rare anomalies but part of the natural spectrum of human biology.

This complexity creates a fundamental problem for sports regulators. If no single biological trait can reliably distinguish all women from all men, then any rule based on a single factor—whether chromosomes, hormones or anatomy—will inevitably exclude some athletes who do not fit neatly within those categories.

In recent years, sports organizations have shifted their focus to testosterone levels as a proxy for athletic advantage. The argument is that higher testosterone provides benefits in strength, speed and endurance, and therefore justifies exclusion from women’s competition.

However, the empirical evidence supporting that claim remains limited and contested. In a landmark legal challenge, Indian sprinter Dutee Chand successfully argued that governing bodies must demonstrate that naturally elevated testosterone confers a significant competitive advantage. The court required sports authorities to provide evidence that the advantage was substantial, not marginal.

Yet, as the COYOTE analysis points out, “this study does not exist.” Despite years of debate and access to extensive performance data, no comprehensive study has been published comparing athletes with elevated testosterone to their peers in a way that definitively proves such an advantage.

This absence of evidence complicates claims that current policies are grounded in settled science. While it is well established that average differences exist between male and female athletes, applying those averages to individuals with atypical biology—or to transgender athletes—remains scientifically unresolved.

The article also challenges one of the most persistent justifications for strict sex verification rules: the idea that men have historically disguised themselves as women to gain an advantage in competition. According to the analysis, “we have no documented case” of such deception at the Olympic level, despite decades of scrutiny and enforcement.

Instead, enforcement of sex testing policies has disproportionately affected women with naturally occurring biological variations, many of whom are Black or brown athletes from the Global South. Human rights organizations have raised concerns that this pattern reflects not only scientific uncertainty but also systemic bias in how policies are applied.

The implications for transgender athletes are significant and complex. Unlike athletes with DSD, transgender women undergo medical transition that may include hormone therapy, which can alter muscle mass, strength and other physiological traits. Some studies suggest that these changes reduce certain advantages, but the available data remains limited and inconclusive.

Compounding the challenge is the small number of transgender athletes competing at the elite level. As a result, there is insufficient data to draw firm conclusions about comparative performance. This lack of evidence has not prevented policymakers from enacting sweeping rules, but it does raise questions about whether those rules are based on empirical findings or precautionary assumptions.

The broader issue, as highlighted in the COYOTE analysis, is that sports policies are attempting to impose rigid definitions on a biological reality that is inherently complex. The assumption that sex can be cleanly divided into two categories—male and female—has long served as the foundation of athletic competition, but that assumption is increasingly challenged by advances in genetics and endocrinology.

Without a clear and universally applicable definition of sex, governing bodies are left to choose among imperfect criteria, each of which carries its own limitations and consequences. Policies based on chromosomes risk excluding women with natural variations. Policies based on hormones raise questions about fairness and medical intervention. Policies based on anatomy are invasive and ethically fraught.

At the same time, athletic performance is influenced by a wide range of factors beyond sex or gender. Genetic traits unrelated to sex—such as those affecting oxygen capacity or muscle composition—can confer significant advantages, yet they are generally accepted as part of natural variation in sports. This raises questions about why some biological differences are regulated while others are not.

The COYOTE article suggests that these inconsistencies reflect deeper assumptions about gender and fairness that are not purely scientific. It argues that without questioning the underlying premise of a strict binary, policymakers risk perpetuating a cycle of flawed policies that are later revised or abandoned.

Ultimately, the debate over transgender athletes is not simply about inclusion or fairness, but about the limits of current scientific understanding. Efforts to create clear, enforceable rules must contend with the reality that biology does not always provide clear answers.

As governing bodies continue to refine their policies, the research suggests that a more nuanced approach may be necessary—one that acknowledges uncertainty, incorporates evolving scientific evidence and considers the ethical implications of exclusion.

For now, the evidence indicates that the question is not as straightforward as it is often presented. Defining who qualifies as “female” in sports is not just a scientific challenge, but a philosophical and policy dilemma with no easy resolution.

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