In a memorable scene from the film “Jurassic Park,” paleontologist Alan Grant stumbles across eggshells and realizes that the park’s dinosaurs — supposedly all female — have been breeding. Remembering the creatures were genetically infused with frog DNA, Dr. Grant recalls that some frogs can “spontaneously change sex.” As another of the movie’s characters famously puts it, “Life finds a way.”
In the animal world, there are indeed amazing species, such as some coral reef fishes, that can switch sexes as adults. As it happens, however, adult frogs don’t happen to be among them, as far as anyone has been able to tell. That said, hundreds of laboratory experiments over the past century have shown that the tadpole offspring of frogs may switch sex before metamorphosing into frogs. This means that any given amphibian may be genetically male based on its chromosomes but have a different expressed sex based on having ovaries, and vice versa. That fact may have inspired the fantasy science in that “Jurassic Park” scene, and it also has prompted real scientists to speak about sex and gender in ways that are culturally loaded — and potentially dangerous.
Biologists — including one of us — too often employ imprecise terminology when describing the biology behind changes in sex, like those seen in amphibians. Many of us have too casually used terms such as “feminize” and “demasculinize” to discuss such shifts. This has led media outlets including CNN, the New York Times and National Geographic to embrace the same vocabulary in stories about the supposed effects of chemical contaminants on amphibian and fish populations. Troublingly, this is the same language that homophobic groups deploy against the LGBTQIA+ community when they’re attacking trans and queer people’s rights to raise families, use bathrooms, access health care or even exist. Sometimes, these two tendencies overlap, as they did when the conspiracy theorist Alex Jones absurdly claimed that the U.S. government puts chemicals in the water that “turn the freakin’ frogs gay.”
There are also material, even dangerous, consequences to binary and heteronormative thinking and careless language, not least of which is that such ideas can mislead us about real biological processes. Most research on sex reversal over the past several decades has focused on contaminants known as “endocrine disrupting chemicals” or EDCs. EDCs have received a lot of media attention because of how they affect the development of ovaries and testes, as well as various genitalia, in frogs, fish and other animals, including mammals. Disturbingly, EDCs are found in everything, from pharmaceuticals to pesticides, to plastics and personal care products, which is how they’ve contaminated much of the Earth’s water, where most frog species spend the majority of their lives. (To the extent that Jones was referring to anything real, it’s probably these pollutants that inspired his profoundly misguided claims about “gay” frogs.)
But you don’t have to be a full-blown conspiracy theorist to be led astray about the dangers of EDCs. Because EDCs can mimic or interfere with naturally occurring hormones, they also interfere with other important biological functions, such as thyroid signaling and metabolic pathways. Nevertheless, EDCs’ reproductive effects — and not, say, the carcinogenic or cardiovascular harms they produce — have received the most popular attention. In other words, fixating on a single issue, such as sex, may be distracting us from other real dangers.
To make matters worse, those concerns about sex-reversing amphibians may be misplaced. Where Jones is explicitly homophobic, even well-meaning research in this field often works from the assumption that amphibian sex reversal is unnatural and/or harmful, as we see when scientists use loaded terms such as “feminized” or “demasculinized.”
However, recent research published in PeerJ (by one of us, Max, and colleagues) suggests that sex reversal may actually be fairly common, even in the absence of chemical contamination. In some cases, frog sex reversal may be human-caused, as a result of EDCs, and may be harmful. But a direct link between EDCs and sex-reversed frogs has been observed only in the laboratory, not in the wild. What’s causing sex reversal in these wild frog populations is not yet clear, but our latest data suggest that natural temperature variation, occurring independently of urbanization or climate change, may be a catalyst. Whatever the harmful effects of EDCs might be, these contaminants may not be causing frogs to switch sex in the wild. Indeed, it’s possible that we perceive sex reversal only as an “unnatural harm” because of our socially conditioned expectations about sex and gender.
But some have also made the more provocative argument that sex is a just a social category, as well, The idea is that because gender is a cultural concept, then sex must be as well, since our ideas about gender derive from our ideas about sex. Whether we’re talking about humans or some other species altogether, sex is also something we assign to every individual. Thinking this way doesn’t mean sexes don’t exist, but rather emphasizes that sex categories — and the decision to organize society based upon sex categories — are cultural constructions. We could have categorized animals based on a variety of other traits. For instance, we might have grouped individuals based on dexterity — whether they are right- or left-handed — or whether they are on average smaller or larger, as a bimodal (or even multimodal) and not binary difference.
Across all life on Earth, sex is expressed in various ways. In fact, none of the commonly used biological markers of sex — chromosomes, gonads, hormones, secondary sex characteristics, genitalia — are binary, or even bimodal, meaning not all “female” or “male” individuals have all “female” or “male” markers, respectively.
To use a human example, drawing from a bioethics discussion about sex assignments in professional sports, some people are born with a condition called complete androgen insensitivity syndrome (CAIS). These individuals have XY chromosomes, testes and levels of testosterone in the typical male range. (All people — along with frogs, fish, birds, reptiles and mammals — produce testosterone; those who are categorized as male tend to produce more, on average.) Thus, on the basis of chromosomes, gonads and hormones, people with CAIS would be labeled male. But because their cells do not respond to androgen, people with CAIS also have breasts and female genitalia; they are generally assigned female at birth, are raised as girls and tend to identify as such. CAIS is one of several intersex conditions that enable people labeled female to produce levels of testosterone closer to the typical male range. Many may be familiar with professional athlete Caster Semenya (who has a different intersex condition), whose case was cruelly, and unscientifically, mishandled by the International Association of Athletics Federations. The non-binary makeup of biological sex markers does not mean that sex can’t sometimes be a useful classifier in research; sex is just more complicated than simply female or male.
Incorrectly conflating “gender” with “sex,” or applying gendered terms to nonhuman animals, isn’t simply a matter of semantics. This kind of language reinforces the notion that heterosexuality is natural and universal, and that all other sexualities are therefore abnormal. When we allow instead for the real possibility that frog sex reversal might be perfectly natural, it’s easy to notice how incorrect it is that we believe heterosexuality and binary sex to be normal, or the default.
First, frogs are not feminine or masculine to begin with — those are human descriptions of the socially constructed human gender binary, not sex. Second, by equating frog sex with human genders and sexualities, terms such as “feminized frogs” exacerbate prejudices against gender nonconforming people. Third, as new research demonstrates, frog sex reversal is not necessarily harmful, and can be quite common in wild populations. When we project our anthropocentric assumptions onto amphibians, we might actually miss what’s good or bad for them.
Synthetic chemicals, including EDCs, may well play a role in this steep decline. Chemical contamination of water presents a serious threat to amphibians given that most species spend much of their lives in water. Such constant exposure to toxins definitely adversely affects the health, reproductive or otherwise, of people and wild animals. Unfortunately, heteronormative assumptions about “normal” and “natural” sex and gender act as blinders, potentially causing scientists and advocates rightly concerned about ubiquitous EDC exposure to fixate on the wrong pieces of the puzzle. EDCs and other synthetic chemicals may be generating more substantial harms that we have yet to grapple with, and sex reversal isn’t necessarily one of them. Given the enormous quantities of poorly understood chemicals supersaturating all of our environments, and given today’s ecological crises of mass population declines, it’s essential that we attend to both social and environmental contexts.
De-gendering our language enables us to learn about the organisms we care about, and which our global ecosystem depends upon, with greater clarity, and without cruelly alienating certain human communities. Both science and society need to break free from our heteronormative fetters to better understand, appreciate and coexist with the stunning spectrum of life on Earth.