This is not my review, thank Ceiling Cat, but it’s one I agree with. Although I’m doing so reluctantly, I’m reading Agustín Fuentes’s recent book Sex is a Spectrum: The Biological Limits of the Binary. Its thesis is, well, pretty much what the title says, although, as you’ll see, the evidence supporting that thesis is nonexistent, at least for biological sex. I’ve read about half of the short book, but then the review below, by Tomas Bogardus (a professor of Philosophy at Pepperdine University) appeared at Colin Wright’s Substack Reality’s Last Stand. This has blessedly relieved me of the need to write my own review, since Bogardus says pretty much what I’d say given what I’ve read so far. Although I haven’t yet finished the book, and may weigh in later, Bogardus’s review is thorough, accurate, and very critical. Although Bogardus works in philosophy, he knows the relevant biology, and, in addition, his philosophy training has helped him spot the logical errors in Fuentes’s book.
Sex is a Spectrum is, as you may have guessed, not really a work of science but one of ideology: an attempt to show people who feel nonbinary that nature justifies their feelings (this is what I call “the reverse naturalistic fallacy”). Note, though, that transsexual people almost invariably affirm the binary of biological sex, as they are born having one natal sex but attempt to change their appearance, behavior, and physiology to mimic those of the other sex. This of course implies two sexes. It is gender activism rather than sex activism that motivates efforts like Fuentes’s. And in his effort to show that animals and plants don’t conform to a biological sex binary, Fuentes gets himself tangled up in a ball of confusion about what he really means by “binary”, “spectrum”, and even “sex.”
You can read Bogardus’s review by clicking below, and I’ll give some excerpts (indented).
Excerpts (bolding is Bogardus’s):
What is “the Binary View”?
It’s clear that Fuentes means to target “the binary view.” But it’s unclear what the binary view is meant to be. The first possibility is suggested by the back cover, which says the book explains “why we can acknowledge that females and males are not the same while also embracing a biocultural reality where none of us fits neatly into only one of two categories.” So, perhaps this is what Fuentes means by “the binary view”:
- Binary View 1.0: Some of us are clearly only male, or clearly only female.
Perhaps Fuentes means to deny this, and to claim that none of us is clearly male, or clearly female. But if Binary View 1.0 is what Fuentes means by “the binary view,” it seems hopeless to argue against it. For surely Binary View v.1.0 is true. I myself am clearly only male, for example. And so are at least some of the wild peacocks that roam my neighborhood. No doubt it’s true that many (all?) of our biological concepts admit of borderline cases. Nevertheless, at least some also admit of clear cases. “Male” and “female” are two examples. [JAC: remember, Bogardus is talking here about biological concepts; later in his review he deals with “disorders of sex determination”]
What Fuentes seems to be trying to express is that while some of us are male and others of us are female, nobody is “neatly” one or the other. Because, as he says on page 36, “bodies, physiology, and behavior are not so easily classified, and are queer indeed.” In other words, while I might be clearly only male, nevertheless, Fuentes thinks, at least some of my sex biology—some of my sex-linked traits—will be had by at least some females. This brings us to the second possible meaning of “the binary view.”
Bogardus gives two other interpretations of “the binary view”. The second is confused and wrong, but here’s the third:
- Binary View 3.0: There are exactly two sexes: male and female.
If Fuentes thinks Binary View 3.0 is false, that would indeed be worth saying, and worth arguing for. That would engage some of the recent discussion in the literature as well as the popular culture. And this interpretation is supported by parts of the text, as we’ll see below. In the book, Fuentes seems to give reasons to think there might be more than two sexes, reasons having to do with mating types, reasons having to do with some birds, and reasons having to do with disorders of sexual development.
Let’s discuss these arguments in turn.
You can see the arguments in turn, but the easiest one to see through, and the dumbest one, is the “argument from birds”. Let’s see what Bogardus says:
The argument from sparrows:
On pages 30 to 31, Fuentes reasons this way:
Like so many other animals, the patterns of how sex biology varies with bird species is dynamic and multifactorial: there are not simply two uniform sex types…. There are even some bird species with multiple ‘sex’ categories. The white-throated sparrow has some changes to its chromosomes that effectively produce four chromosomal types that have different plumages and a mating system wherein certain types are not compatible with others. So, while there are only two gamete-producing physiologies in the species, there are functionally four sexes in the reality of the actual mating system.
The idea seems to be that this species of sparrow features multiple sex categories, indeed that there are “functionally four sexes” in this species. And the reason is that, allegedly, males with a certain plumage are not reproductively compatible with females of a certain plumage.
First of all, there are only two biological (gametic) sexes in the white-throated sparrow, as everyone who works on it recognizes—and mentions in their publications. There are, however, two color and pattern morphs of each of the two sexes. There is disassortative mating between the morphs, but it’s not complete, as Fuentes mistakenly says. Regardless, this, and similar examples of different morphs of the sexes, do not refute the biological sex binary (based, again, on gametes); they just show variation within each of the two sexes.
Here’s where Bogardus’s philosophy expertise enters:
But does Fuentes really think that there are more than two sexes? On the one hand, it seems like he does. Recall that Fuentes says that mating types are often called “sexes,” and there are thousands of mating types. He says that there are some bird species with multiple “sex” categories. And he says that the binary view of sex “does not allow space” for people like Caster Semenya. Together, this seems to me like powerful evidence that Fuentes means to argue that there are more than two sexes. Sarah Richardson (2025, 437), in a recent review of Fuentes’ book, reads him as saying that “there are not only two sexes, and sex can most definitely change.” So, there’s at least one prominent ideological ally who hears Fuentes talk out of that side of his mouth.
But, out of the other side of his mouth, he tells a very different story. On the podcast Academics Write, published on June 19th, 2025, at the 9:25 mark, Fuentes says this about his book: “And so I’m not saying there’s [sic] more than two sexes—there are male and female, that’s how we’re talking about it. But male and female are not essential, distinct entities compared to one another. They’re typical clusters of variation. And within each of those typical clusters, there’s huge variation.”
What are we to conclude from all this?
Unfortunately, it seems me the best explanation is that Fuentes’ view is not clear even to himself, and that he vacillates between a controversial and implausible claim that there are more than two sexes, and the modest and uncontroversial claims that sex-linked traits are often shared among both females and males, and that sex-linked traits vary significantly among males and among females. That is, Fuentes conflates an interesting but false thesis with a trivially true thesis, retreating to the latter when the former is challenged. A motte and a bailey, one might say.
This conflation is the usual argument against the binary: that because there is variation among individuals of a sex within species in some sex-related traits (e.g., penis length, breast size), and also among species in the way sex is determined or expressed (temperature in some reptiles, chromosomes in homeotherms, but in different ways in birds vs. mammals, haploidy vs diploidy in bees), there must be more than two sexes. But if you’re going after the gametic sex binary, which is how biologists conceive of the sex binary, this is a fallacious form of reasoning. All of this variation fails to efface the stark fact that there are two types of gametes and no more: eggs and sperm. Although there are some hermaphrodites that make both, most animals have individuals with the reproductive equipment evolved to produce only sperm (males) or only eggs (females). There is no third type of gamete.
And this binary was not made up by biologists who are “transphobes” and want to erase people of non-standard gender: it is an observation that’s been made for well over a century and was clarified when eggs and sperm were discovered. As Richard Dawkins has elegantly pointed out, the gamete-based definition of biological sex is both universal and utilitarian: it holds in all species of animals and vascular plants, and explains a number of otherwise puzzling biological phenomena, like sexual dimorphism that arises from sexual selection.
Yes, of course the carriers of two types of gametes show intra-sex variation, but so what? What is remarkable is that variation is ubiquitous in the natural world—except for the types of gametes produced within most species (we are ignoring “mating types” in some simple organisms, though Bogardus covers that).
Fuentes also stumbles when he encounters sequential hermaphroditism:
What is a sex?
Let us turn now to the question of what a sex is, according to Fuentes. In this book, he seems to endorse a gamete-based account of males and females. On page 1, we read this:
“Imagine you are a fish called a bluehead wrasse… You are what we’d call female, so you produce eggs. There is only one very large member of your group, and they are the group male, so produce sperm.”
And on page 29 he moves seamlessly between these two descriptions:
“There are species [of reptiles] where females are larger than males…, others where males are larger than females…, and yet others where there is little or no size difference… …it’s likely that both competition between small-gamete producers… and environmental constraints on body size (for both small- and large-gamete producers) are involved.”
This happens again on pages 33-4:
“Similarly, there is a whole group of primates that challenges the expected roles of large- and small-gamete producers. Most primates live in big groups of several males and females and young, and others live in groups of one male and many females and young….”
So, it sure looks as though Fuentes admits that the sexes are defined in terms of gamete production: females are “large-gamete producers,” and males are “small-gamete producers.” One might think, then, that Fuentes would define having a sex more generally as the producing an anisogamous gamete-type (sperm or eggs).
And yet he does not do that.
What a pity that someone who is clearly intelligent has twisted up his neuronal wiring to deny what he really realizes! Like the clownfish, the blue-head wrasse has sequential hermaphroditism: one sex can become another depending on age and social milieu: but there are always just sperm producers and egg produces. Two sexes, no more! And yet there are those benighted individuals, believe it or not, who think that this sequential hermaphroditism refutes the gametic binary. I pity them deeply.
As you see, I’m getting tired of repeating these arguments over and over again, so I’ll draw to a close. What irks me the most is that this is not an argument about biology, it is an argument about semantics, and one that has already been resolved. It has been revived not because some new biological facts have appeared, but because gender ideology has surfaced. Ergo the desire of people (well-meaning though they may be) to change biology so it conforms to an au courant gender ideology.
And here I’ll leave you to read the review for yourself, and, later on, I’ll wearily drag myself back to the book.
“Fuentes conflates an interesting but false thesis with a trivially true thesis, retreating to the latter when the former is challenged.”
I suggest that no one has ever said it better.
Daniel Dennett labeled this a “Deepity.” A statement is ambiguous and seems profound because a true-but-trivial interpretation provides cover for a false-but-extraordinary interpretation.
“Sex is a spectrum.”
Similar to Steven Colbert’s “truthiness”.
Similar to Paul Edwards’ critique of Heidegger’s writings on death- if interpreted as something profound, it is clearly false. If interpreted as true, it’s trivial.
I read a fair bit of critical theory applied to archaeology while finishing my PhD in 1990.
This sort of thing occurred over and over again, which I christened the “Obvious, Ludicrous or Ambiguous” principle. Everything they said was either Obvious or Ludicrous, or it was Ambiguous as to whether it was Obvious or Ludicrous.
Sadly I never wrote this down as I decided that it wasn’t relevant enough to the study of animal bones.
Bogardus calls it “shadowboxing.” To me it’s an example of the Smokescreen Fallacy. Very well-written and argued critique.
The main thing that bothers me about this entire dispute—and Fuentes’s position in particular, as he is a major player—is whether the proponents are simply wrong or whether they are disingenuous. To me that makes all the difference in the world. To err is human, to lie is a travesty. If Fuentes reads and understands Bogardus’s criticism, and he continues to produce books, and articles, and commentaries decrying the sex binary, he will reveal the side of that line he inhabits.
I think Fuentes and other intelligent, educated people who support this “sex is binary” argument are sincere in the same way intelligent, educated people who believe in God are sincere. They’ve learned to doublethink when a conclusion is seen as sacred, a matter of identity, or useful for some crisis, real or imagined.
“Of course I don’t believe in a deity above who grants wishes, that’s a strawman version of the sophisticated, nuanced understanding of the Ground of Being which I accept …. Oh dear Jesus, please help my suffering child.”
It’s very blurry.
The analytic philosopher Harry Frankfurt called this “bullshit” and distinguished it from lying. A lie is a falsehood told with the intent to mislead the listener with a claim that’s known to be false. Bullshit is a falsehood told with indifference to the falsity or its effect on the listener, because expressing the falsehood has some purpose other than convincing the listener of the false belief. The bullshitter doesn’t much care whether what he says is true or false.
“A student trying to sound knowledgeable without having done the reading, a political candidate saying things because they sound good to potential voters, and a dilettante trying to spin an interesting story: none of these people are trying to deceive, but they are also not trying to convey facts. To Frankfurt, they are bullshitting.”
Hicks et al. (2024) ChatGPT is bullshit. Ethics and Information Technology 26:38
https://doi.org/10.1007/s10676-024-09775-5
A charitable view is that Fuentes’ purpose is to convince the listener that Fuentes is a Good Person.
I honestly don’t see how “sex is a spectrum” is anything more than mere meaningless wordplay. I could equally well argue that dogs and cats are not distinct categories but rather are “on a spectrum”. I have occasionally met dogs with strangely cat-like personalities and, somewhat more often, cats quite dog-like in their temperament. Clearly our beloved quadrupedal friends manifest a variety of different characters and personality traits. But I never felt the least bit confused about the dogness of dogs and the catness of cats. Nor do the animals ever seem confused.
Yes! We had a cat who would play fetch with us. Our current dog is not good at that game, but he loves to stretch out languidly along the back of the couch.
So our pets are a spectrum!
I’d like to know what Fuentes means by queer in this sentence: “‘bodies, physiology, and behavior are not so easily classified, and are queer indeed.'”
Also, this is probably just lax writing, but the sentence “You are what we’d call female, so you produce eggs” seems to imply that because we call them female they produce eggs. It should really say ‘Because you produce eggs, we call you female.”
Obviously you are unfamiliar with the scholarly discipline known as “queer theory”. I commend to you that you correct your ignorance at once and read the profound works of those revolutionary thinkers Michael Foucault, Judith Butler and other great scholars of that discipline. Or, if you are less ambitious, you could simply peruse Wikipedia’s page “Queer Theory”.
To answer your question, when the word “queer” is uttered by a lefty flake, when they speak of the goal of “queering society”, they don’t mean that we all must be gay. They mean that we should be unconventional, and “transgressive”, and aspire to defy patriarchal societal norms particularly as regards gender and sexuality. But the meaning of the word “queer” is deeper than that. Some brilliant scholar recently published a highly regarded paper explaining that babies are inherently queer. Indeed, queerness is the natural state of humanity. Scholars of queer theory teach us that indigenous peoples never had a concept of a gender binary or any other such unenlightened ideas prior to their brutalization and cultural contamination by patriarchal colonialist European oppressors. The word queer doesn’t even need to apply to a human being. Somebody published a paper arguing that ornate umbrellas are inherently queer. (Don’t think I am exaggerating, I am not!)
If you don’t grasp the concept of queerness in all its ineffable glory, it is because your thinking is rigid, perhaps even “19th century”. Only truly enlightened people whose philosophy is liberatory and Postmodern can grasp the concept of queerness.
I am familiar, which is why I wondered at how he was using it. I assumed he meant it in that context, but, not having the book, am unsure of whether he explains that that is how he is using the word.
I suspect that Fuentes quite deliberately and with intellectual malice aforethought used the word “queer” as a double entendre. He used the word knowing that some lefties would love it and read it with Postmodern meaning. But then if pressed he could claim that he just used the word “queer” in its old meaning as synonymous with “odd” or “strange”.
He’s paraphrasing Haldane (whether as a double entendre or not):
“Chapter 11 of one of my favorite books is titled “Beyond the Binary: Evolution’s Rainbow,” and it opens with a quote attributed to the twentieth-century evolutionary biologist J. B. S. Haldane: “The universe is not only queerer than we suppose, it is queerer than we can suppose.” Here “queer” means strange, fascinating, different, confounding of expectations. This quote is fitting for the reality for sex biology. Gametes (sperm and ova) in most animals can be described as binary, one large and one small. But bodies, physiology, and behavior are not so easily classified, and are queer indeed.”
Fuentes, Agustín. Sex Is a Spectrum: The Biological Limits of the Binary (p. 36)
I was having a similar idea, where even though the inaccurate biology comes thick and fast in the book, those who want to believe in the non-binary will simply not notice the wrong parts and the clearly contradictory parts. He does not have to be careful or accurate with this audience. He just has to reassure them.
I tried to get my head around Queer theory a few years ago. Even read the aforementioned wiki on it.
(sigh) It nearly did my head in. I decided I was too white, too male, too non-disabled, too straight, too sane…and too bright.. to ever be able to access it.
Maybe I should work on my “mar-gin-al-i-zation” (if I didn’t hate that word SOOO MUCH) if I take another run at it.
I won’t.
🙂
D.A.
NYC
-happily unqueer.
Just two short items:
1. The old phrase ‘nought queer as folk.’
2. If Haldane said what Mr. Hagen quotes, then old J.B.S
is asserting something he has just said is impossible.
Dr B: The below post was originally in response to you, with an apology should you already know the matter. I deleted it because I saw your reply to Michael that had posted a minute or two earlier. But I’ve reconsidered. I still routinely encounter people, usually older, who take the jargon and other woke buzz words, translate them back into 1960s-1980s Democratic Party speak, and then wonder what all the fuss is about. Thus, equity becomes equality, queer becomes gay or unusual, etc. And then they rant at those who they presume oppose “equality” and “gays.” Maybe the below, along with what Michael says above, can show the pitfalls of that path should any readers lack your familiarity with “queer theory.”
For Fuentes to call “bodies, physiology, and behavior” queer, I presume he is word-dropping jargon in a nod to ideological allies. Queer in this sense simply denotes that behaviors are diverse, physiology complex, bodies not binary. But queer can also presuppose conceptual fluidity and a theoretical resistance to fixed categories. The idea behind the jargon is that binaries justify hierarchies, one side of the binary is privileged (superior, normal) while the other is marginalized (inferior, abnormal). So, the purpose of transgression, as Michael notes, is to destabilize the binary, thus disrupting the supposed power structures that maintain the privilege. The language games are nothing more than attempts to destabilize through words, a belief that words shape reality rather than simply describe it. One can speak, or “perform,” gender into being. It’s a mystical conjuring act, but they believe it no less real for the magic.
…or to simply wreck, burn down or destroy everything that works. And everyone that works because Queer Theory’s goal is to pick out areas where the systems that have provided such freedom, food and flourishing for so many humans over the last few centuries… have some faults. It is, in essence, a kindergarten level of intellect mixed with narcissism.
D.A.
NYC
Comment by Greg Mayer
I wish Bogardus had used the term “sex-associated” or “sex-related” (as Jerry did in commenting on the review). “Sex-linked” has a rather specific meaning in genetics that is used widely in biology: a “sex-linked” gene (or trait whose state depends strongly on such a gene) is a gene on one of the sex chromosomes. Hemophilia is sex-linked; height is not.
GCM
Yes. A quick reading led me to think of “sex-linked” in terms that a geneticist would use.
There was also a review of the book by the evolutionary psychologist Ed Hagen, but the link seems to not be working anymore (https://blog.edhagen.net/posts/2025-08-07-review-sex-is-a-spectrum/).
It’s worth reading for those who manage to get access.
It works for me. Furthermore, I posted on that very review just a few days ago in the Nooz:
https://whyevolutionistrue.com/2025/08/29/friday-hili-dialogue-539/
People should keep up on their reading. The Nooz is where I put all the stuff that’s important or interesting but doesn’t merit a full post (actually, Hagen’s review did).
Ed Hagen is an anthropologist — it might be important to point out that not all biological anthropologists buy into Fuentes’s point of view!
Thank you for reading this book and promoting reviews by subject matter experts; comments and reviews by you and other subject matter experts are critical for me and my hoi polloi friends to understand the issues. I made a similar effort onCoates’ and Kendi’s word salads, an effort that has paid off greatly in my and my friends’ understanding over the past decade of wokification
Ergo the desire of people (well-meaning though they may be) to change biology so it conforms to an au courant gender ideology.
I am no longer willing to give good intentions a pass when it comes to intellectual integrity. There is nothing noble about lying.
Very clearly laid out.
It is a good moment to haul out this quote (regarding Fuentes):
“…its author can be excused of dishonesty only on the grounds that before deceiving others he has taken great pains to deceive himself. ” Sir Peter Medawar
And yet…. Fuentes’ kind of thinking is by now the dominant position, at least here in Canada and the US. Well educated individuals, young and old, espouse this way of thinking in large numbers. To me it seems to be a plurality and more importantly this plurality dominates the top echelons of the political and scientific establishments.
It’s as if, the decision makers and the educated population converted to a new religion while carefully denying that any such thing has occurred. The new creed has no name, no bible, and no prophet so there is no new creed. Anyone who says otherwise is an infidel, although since there is no creed there can be no infidels, so anyone who thinks that sex is binary is simply an anti-social right-wing a-hole.
Of course many people just go along with the BS while hiding their doubts and derision from public view. Who wants trouble in the family or a wrecked career after all? Who wants to be labelled a hater by one’s children?
Ah modernity… First the H-bomb and now this. Sometimes I am happy that I am old.