Skip to content

From Banana Slugs to Human Beings, There Are Just Two Sexes

An examination of 18 supposedly ‘trans animals’ disproves activist claims that we all live on a non-binary gender ‘spectrum.’

· 10 min read
Photograph of a clownfish against a background of sea vegetation
A clownfish photographed in Indonesian waters by Christian Gloor.

Pity the poor clownfish—a brightly coloured creature, once made famous by the 2003 animated film Finding Nemo, which has now been reduced to a prop in the ongoing debate about sex and gender identity. That’s because, unlike mammals (including humans), clownfish are what scientists call “sequential hermaphrodites” of the protandrous variety. What this means is that while every clownfish starts out as male, some switch sexes if a female is needed by the school.

Yes, There Are Trans Animals
Many people think that there’s an absolute biological distinction between males and females. These animals prove them wrong.

Anyone who’s followed the debate about transgender rights will immediately understand why this type of fish now has a starring role in advocacy materials designed to convince the broad public that sex-switching is a common feature in the natural kingdom, including among humans. In Canada, for instance, the publicly funded CBC is airing a documentary titled Fluid: Life Beyond the Binary, in which the self-described “non-binary” host, Mae Martin, invokes the existence of clownfish, and various other creatures, to argue that “each of us are on the gender spectrum.” Not surprisingly, Martin is explicitly promoting the documentary as a paean to social justice, and as a rebuke to anyone seeking to put limits on “gender-affirming health care” (such as the double mastectomy that Martin publicly announced in 2021).

Mae Martin explores the science of gender and sexual fluidity in a new episode of The Nature of Things | CBC Documentaries
In Fluid: Life Beyond the Binary, the non-binary Canadian comedian explores the latest discoveries in humans, other animals and plants

This week, British human-rights campaigner Peter Tatchell tried to advance similar arguments in a widely read tweet referencing—as the linked Gay Times article put it—“18 animals you didn’t know were biologically trans.”

“These animals show that gender is not a simplistic binary, male and female,” Tatchell gushed. “Trans and intersex are real. Get used to it!”

Indeed, the article that Tatchell cited goes further, denouncing the very idea of “biology” as a “pseudo-intellectual” fixation of “lesbian separatists” and “right-wing lobbyists.” The author, one Fran Tirado, warns that even mentioning terms such as “biological sex,” “biological male,” and “biological female” is a problematic affront to the supposedly non-binary, gender-bending nature of life—which, the author claims, has been in evidence since “the earliest recorded histories of the earth.”

Then comes the promised 18-point catalogue of “animals you didn’t know were biologically trans”—starting with the above-pictured clownfish (often described by scientists as anemonefish).

So let’s take a look at the list. Are these really examples of animals that are “biologically trans”? And what do they tell us—if anything—about the associated activist claims that sexual dimorphism in humans is just a myth created by transphobic bigots?

Latest Podcast

Join the newsletter to receive the latest updates in your inbox.


On Instagram @quillette