Sex is one of the major cultural and political fault lines of our time. Legislation aimed at regulating who may participate in different arenas of society, including girls’ and women’s sports, is being passed with some regularity. These legislative efforts tend not only to conflate sex and gender but also to jumble up biological traits such as hormone levels with behavioral/performance features such as sprint speed or jump height. Disputes arise in part from confusion and disagreement over what is meant by “sex.”
Within academia, disagreements about sex recently came to a head when the American Anthropological Association (AAA), the world’s largest professional organization for anthropologists, and the Canadian Anthropology Society (CASCA) removed a panel discussion entitled “Let’s Talk about Sex Baby: Why Biological Sex Remains a Necessary Analytic Category in Anthropology” from their upcoming annual meeting. The panel was submitted for review and initially accepted in mid-July. It was then removed in late September, following concerns in the anthropological community that the panel conveyed antitransgender sentiment and decrepit ways of thinking about human variation.
Both among the general public and in academia, the core argument boils down to the question of how many sexes exist. The tricky thing is that the answer to this question differs depending on the context. One perfectly accurate response is: “To a first approximation, zero.” The vast majority of life-forms—including bacteria and archaea—do not reproduce sexually. But if the question concerned the number of animal sexes present in a given tide pool or backyard garden, the answer would need to account for organisms that switch sexes, sometimes mate with themselves or switch back and forth between sexual and asexual reproduction. When we ask, “How many sexes are there in humans?” we can confidently answer “two,” right? Many people think sex should be defined by a strict gamete binary in which a person’s sex is determined by whether their body produces or could produce eggs or sperm. But when you are out and about in the human social world, are you checking everyone’s gametes? And what of the substantial number of people who do not produce or carry gametes?
On supporting science journalism
If you're enjoying this article, consider supporting our award-winning journalism by subscribing. By purchasing a subscription you are helping to ensure the future of impactful stories about the discoveries and ideas shaping our world today.
We think the ongoing discussion about sex might benefit from a fundamental change in approach by turning the question around such that we ask, “If ‘sex’ is the answer, what was the question?”
The value of this approach becomes clear when you consider the long-running debate in biology over how to define species. One definition, the biological species concept, posits that species are groups of actually or potentially interbreeding organisms capable of producing fertile offspring. It is not universally applicable because, as noted earlier, most organisms do not reproduce sexually. It does, however, provide a framework for asking questions about how sexually reproducing organisms can evolve ways to avoid mating with organisms distinct enough that their offspring’s survivability or fertility would be compromised. This framework has led to a bounty of work demonstrating that speciation in organisms living in the same area is rare and that physical separation among groups appears to be a key component of evolving reproductive barriers.
We can extend this “ask questions first” framework to concepts about sex. When it comes to sexually reproducing organisms, several classes of questions fit nicely into a binary view of sex. Others do not.
Binaries are indispensable when asking evolutionary questions about many sexually reproducing organisms. Sometimes the questions asked rely on a strict binary because that is the nature of the relevant existing data—for instance, data from historical and contemporary demographic reports. We have to appeal to a multiplicity of binaries, however, because sexual reproduction has evolved many times and in many different ways across the living world. Reproductive capacities in birds and mammals largely involve inheritance of different combinations of sex chromosomes, whereas in many reptiles, sex is determined based on environmental cues such as temperature.
Binaries start to fail us once we move into questions about how organisms live out their lives. This can be seen in the example of transgender athletes. Arguments revolving around including or excluding trans athletes often rest on notions of strict binary differences in hormone type and concentration that associate female individuals with estrogen and male ones with testosterone. This assumes testosterone is at the root of athletic performance. These hormones do not hew to a strict binary, however. Female and male people need both estrogen and testosterone to function, and they overlap in their hormone concentrations. If we are interested in how estrogen and testosterone affect athletic performance, then we need to examine these respective hormone levels and how they correlate with athletic outcomes. We cannot rely on gross average differences between the sexes as evidence for differential athletic success. Adherence to a sex binary can lead us astray in this domain of inquiry.
Further problems arise when we compare humans to other species. Some organisms are incapable of reproducing. Some that are capable may end up not reproducing. Others may alternate between reproducing asexually and sexually, and still others may switch sexes. Such organisms provide fascinating insights into the diversity of life. But when we refer to clown fish changing sex to emphasize the diversity of ways in which sexual beings move through the world, we risk losing sight of the issues of consent, autonomy, well-being and self-determination that form the bedrock of all dimensions of human health, sexual or otherwise.
As scientists who study evolutionary genetics and human physiological responses to extreme environments, we have a strong interest in understanding the varied presentations of features that we think of as being related to sex. The questions we ask about sex in our research are different from those used in a health context, such as practicing gender-affirming care through erectile dysfunction medication or pubertal hormones. Scientists like us would do well to embrace intellectual humility and listen carefully before deciding that any one definition of sex is useful for understanding the living world.
So, if “sex” is the answer, what is the question? This is not so clear, and we have no warrant to make authoritative declarations on this issue from a scientific standpoint that is uninformed by ethical, moral or social considerations. We are in good company here because sex encompasses such a range of questions that we doubt any one medical, scientific or humanistic practitioner would be able to come up with a question that encompasses all of the ways in which humans are affected by sex, however it is construed.
This is an opinion and analysis article, and the views expressed by the author or authors are not necessarily those of Scientific American.