Activists Who Compare Humans To Sex-Changing Fish Don’t Go Far Enough

If gender activists insist on taking life lessons from hermaphroditic fish, they should follow their reasoning to its ultimate conclusion.

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About the Author

Frederick Prete is a biopsychologist in the Dept. of Biology at Northeastern Illinois University. He teaches courses in neurobiology, and human and animal physiology. He has also served as an associate editor for the International Journal of Comparative Psychology. Prete writes about how people use and misuse biology to support their social and political points of view. 

Other essays by Prete can be found on his Substack Everything Is Biology.

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The contemporary “debate” (if one can call it that) surrounding the biology of sex suffers from a lack of intellectual seriousness on one side. The arguments forwarded by those insisting on the non-binary nature of sex often demonstrate a rudimentary understanding of basic biology, or are so comically nonsensical that one wonders whether they’re even worth responding to. Academic biologists engaging with gender activists’ arguments for the so-called “sex spectrum” are like mathematicians engaging with numerologists (individuals who believe in a mystical relationship between numbers and coinciding events) or geologists debating Flat Earthers. However, given that sex pseudoscience has somehow taken over academia, serious scholars now find themselves compelled to engage with the absurd.

One such example is the bizarre suggestion that because some fish can literally change sex during their lifetime, then perhaps humans can too. This idea, while absurd on its face, is far from fringe. It has been given credence by popular science outlets like Scientific American, which highlighted the sex-changing abilities of clown fish “to emphasize the diversity of ways in which sexual beings move through the world.” Even the United Kingdom’s national library posted (and later deleted) a thread on X during Pride Month last year about the sex-changing abilities of the Māori wrasse, and Greenpeace made a similar move in 2021.

What relevance does LGBTQ+ Pride Month have to sex-changing fish unless there’s an intention to suggest that these examples illuminate the potential for sex changes in humans? But if activists insist on making such far-fetched comparisons, they should be challenged to follow their logic to its ultimate conclusion.

Let’s be honest, animals do a lot of weird things. They enslave other animals, eat their offspring, cannibalize their lovers, kill their newborn twin sisters, and devour their siblings in the womb. Do any of these activists want to justify slavery or embryonic cannibalism because animals do it? Probably not. But it’s equally silly to claim that we can derive grand lessons about human biology and sexual behavior from animals. Male octopuses, for instance, grab a packet of their own sperm with one of their tentacles, shove inside a female’s mantle cavity, and drop it next to her oviduct. This hardly seems like a behavior humans should try to emulate. Are there any objections? Why, then, would we think that fish sexual biology is a better model for us humans than that of octopuses?

What’s more, it frustrates me that those who continuously discuss sex changes in fish don’t get the fish-sex story straight in the first place. In reality, sex changes among the roughly 20 families and seven orders of teleost fish are driven by physiological and hormonal events that are triggered—depending on the species—by factors such as body size, perceived social status, or (in the monogamous clown fish Amphiprioninae) the disappearance of the large, breeding female. It’s also the case that those big, newly minted, dominant female clown fish are viciously aggressive to any fish they do not recognize as part of their group. So, if we’re taking our cues from clown fish, let’s not be hypocritical—let’s go all the way and demand that only extremely large, dominant, hyper-monogamous people who are particularly xenophobic should consider a sex change, and only after all the other females in the neighborhood have vanished. Does that sound reasonable? (I trust you realize I am being facetious here)

It should go without saying, but it appears that some still need a reminder: people are not fish. Fish live in the water. People live on land. When it comes to sex and reproduction, this makes all the difference in the world. In aquatic environments, you can simply release your gametes (eggs and sperm) into the water and let them drift around until they hook up. That’s because, in water, they won’t dry out and die. And neither will your embryos because they’ll be in the water, too. This is why so many fish can produce eggs or sperm at different times in their lives. It doesn’t take any specialized external organs to squirt gametes into the water, just a gonad for gamete production and an orifice for release.

However, the whole situation changes if you live on dry land. As mammals evolved for terrestrial life, they had to acquire adaptations—both structural and behavioral—to prevent their gametes and embryos from drying out. You can’t simply drop your sperms and eggs on the ground and hope for the best. So, male terrestrial animals evolved specialized external body parts for transferring sperm directly into females, who, in turn, have evolved body parts designed for receiving sperm and a chamber for nurturing the developing embryo until it is ready for life on dry land. Additionally—and equally important—both males and females evolved complementary neuromuscular behavioral patterns that allow them to court and mate successfully.

That’s why terrestrial mammals can’t change sex like some fish do. Such a transformation would require females to spontaneously sprout some kind of tube for internal sperm delivery, and males would need to somehow develop a complementary orifice. Moreover—and more importantly—both males and females would need to develop all the necessary internal parts and “plumbing” to make these external structures functional. It’s insufficient to merely alter the appearance of external structures, which can be done surgically (even on pets). A terrestrial animal transitioning from a female to a male would also require developing a complex duct system linking the gonads to the external tube, along with glands to secrete a carrying fluid and nutrients for the sperm (i.e., the Wolffian duct system, prostate, and bulbourethral glands). Going from male to female would involve developing some kind of organ to catch the eggs when they get released into the abdominal cavity, retain them until they encounter sperm, and then house the resulting embryo while it develops (these are derivatives of the Müllerian duct system).

Obviously, none of this could happen. When it comes to mammals, the die is cast prenatally. So, whatever fish do is their business and has absolutely nothing to do with terrestrial mammals. So, let’s drop the clown fish and Asian sheepshead wrasse analogies. Anybody who brings them up simply doesn’t understand evolutionary biology. It is futile to engage in discussions based on such analogies unless, of course, you’re one of those people who think that because some animals reproduce parthenogenically, humans should simply stop having sex altogether and hope for the best.

I want to make it clear that I have a deep understanding and empathy for those of us, including myself, who do not fit the popular stereotypes of any category or group. Throughout my life, I have received what seems to be an unrelenting stream of criticism for the fact that I was never (and still am not) perceived as representative of the norm (whatever that is). Consequently, I grew up defending those who were similarly targeted, and I believe that each of us should be continually mindful and accepting of the rich diversity of the human condition. Each of us should actively and consciously strive to be as compassionate, accepting, supportive, and inclusive as possible.

However, doing so does not require us to abandon reason, turn our backs on biology, or unhinge ourselves from reality.

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