It looks like Natural History magazine has given an implicit endorsement—or at least a platform—to Princeton anthropology professor Agustín Fuentes. We’ve met him before, and not under pleasant circumstances, as the man is wont to distort science and mislead his readers in the cause of progressive ideology. To see all the pieces I’ve written about him, go here (and especially these pieces here, here, and here. And for critiques of Fuentes’s misguided accusations that Darwin was a racist who justified and promoted genocide, go here and here, and also see here for one I published in Science with a bunch of evolutionists. Some of these articles show Fuentes deliberately purveying misleading statements to buttress an ideological position. For that seems to be his modus operandi.
Now Fuentes has put his view that sex is not a binary into a new book, an excerpt of which was published in the latest Natural History, a magazine I always liked. This single bad article won’t change my mind about it (as the multiple bad articles in Scientific American did about that rag), but it makes me question the editors’ judgment. Do they know ANY biology? The reason I ask is that the excerpt is so tedious, dreadful, tendentious, misleading, and convoluted that it wouldn’t pass muster in a real scientific journal, and even a scientifically ignorant editor could see the problem with the arguments (and also correct the bad writing).
You can’t go to the article by clicking on the headline; and I don’t have a link, either. I was sent a pdf by a disaffected reader, and that’s what I’ll quote from. Perhaps you can find a copy if you dig around.
The overweening problem with this article is that it doesn’t show that the binary view is wrong, or that biological sex is really a spectrum. What Fuentes does (and he doesn’t really define biological sex) is to show that within the two constructs he takes to represent sex, there is a lot of variation in various traits. Men don’t all behave in a way that differs from the way all women behave, development of sex is complicated, people of different sex have different “lived experiences” (yes, he says that), the structure of families vary among cultures, and so on.
But of course all of this variation, and the multidimensional definition of sex, neglects the big problem: is biological sex binary? Yes it is: males have reproductive systems that evolved to produce small mobile gametes (sperm) and females have systems evolved to produce larger immobile gametes (eggs). There are only two types of gametes—no more. Biologists have arrived at this definition for two reasons: it’s universal in all animals and plants, and also because of its utility: the different investment in gametes usually leads to differential investment in offspring, which explains not only sex differences in behavior, but sexual selection itself, which produces sexual dimorphism in appearance and sexual behavior. The exceptions to a strict binary defined (really “recognized”) this way range from about 1/5600 individuals to 1/20,000, and that’s as close to a binary you can get in biology.
What Fuentes does is throw a lot of sand in the reader’s eyes, showing variation within sexes and across cultures, hoping that at the end the reader will say, “Hey, maybe sex isn’t a binary after all.” But that variation does not touch the thesis he’s trying to depose. The man doesn’t know how to debate, so, like a true ideologue, he changes the ground of argumentation.
First (probably in the nonquoted parts of his book), he defines the sexes in an introductory note as “3Gfemales” and “3Gmales”, referring to “typical biological patterns of association between genetics-gonads-genitals in human bodies.” I presume he means that members of each have has the typical chromosomal constitutions of its type (e.g. XX in females) as well as gonads (that presumably means testes vs. ovaries) and genital morphology. Fuentes adds that “while useful as general categories, not all people fit into the 3G classifications.” So that is his definition, and of course since it involves more than gametes, will naturally be less binary than the biological definition. A male with a tiny penis, for example, perhaps because of a disorder of sex determination, would be called a biological male if he has testes, but is something else according to Fuentes. But Fuentes doesn’t say what such an individual is. How many sexes are there? An infinite number? And is that true of raccoons, Drosophila, and robins?
Okay, here comes the sand, so cover your eyes. I’ll have to use screenshots since I can’t copy and paste from this pdf:
Variation in sexual behavior:
But it is not “human sexuality” that is the binary, but the definition of sex. Surely Fuentes recognizes that he is deviating from the main issue his book (and this article) is about: the binary nature of defined sex, as seen in every species of animal and plant. That doesn’t mean that sexuality and its expression is binary. I’m not sure whether there’s a name for this kind of argumentation, but what he’s doing is clear.
He drags in variation in family structure, too:
Again, all this does is refute a binary of families, not of sexes. Why is it in there? What is the sweating professor trying to say?
Fuentes dwells at length on how sex is basically irrelevant in medicine because sexes show variation in their responses to drugs and get diseases at different rates, implying that the binary is all but useless for doctors. I read to my doctor several paragraphs of Fuentes’s screed, and I won’t give his reaction save to say that it was “not positive.” For example, can you even understand this?:
Stable? “Perceived instability”? What is he banging on about? He doesn’t say.
And females are too complicated to deal with in biology, medicine, and health? What is he talking about? When a patient goes to see a doctor, it’s essential for the doctor to know the patient’s biological sex. Not only are some diseases specific to sexes (prostate cancer, ovarian or uterine cancer) as are some conditions (menopause), but a good doctor will realize that heart disease (and other diseases) can present differently in the sexes, and will investigate further based on that. Females with heart disease, for example, present more often with indigestion-like symptoms than do males. Now of course there are factors other than sex involved in treating a patient (do they drink, smoke, or eat too much?), but saying that sex is pretty much useless when treating patients is simply dumb. It can even be harmful (though he doesn’t say how):
Again, does any doctor pay attention only to sex? I don’t know of one. To be sure, Fuentes grudgingly admits that there are “two sets of reproductive physiologies” that are relevant to medicine, but minimizes the importance of sex. And to be sure, some diseases are recognized and treated identically in males and females, but to ignore biological sex as a doctor is sheer incompetence.
In another example, Fuentes notes that Ambien doesn’t work the way you’d predict in women if you just reduces the male dosage based on a smaller weight of females. Why doesn’t this work? Because the drug clears from women “3G females” (did the doctors check all the “G”s?) more slowly than from “3G males.” He uses this difference to attack the sex binary, by saying that we don’t understand why this average difference occurs, saying “asking about the actual physiological response, rather than assuming 3G males and 3G females are different kinds of humans, is a better approach.”
But again, this is irrelevant to the sex binary; it is about the mechanism of a difference between (Fuentes’s) biological sexes. And, interestingly, one of the mechanisms he suggests is “attention should be focused on the varying levels of acting testosterone in attenuating the effectiveness of [Ambien].”
Testosterone! Well at least that has some connection with biological sex, no? Fuentes then tries to efface the difference in hormone levels by saying this: “Testosterone is not characterizable as a male or female hormone, but rather by variation in circulating levels among humans, with 3G males usually having much higher levels than 3G males.”
In reality, we’ve long known that both testes and ovaries produce testosterone, but the distribution of salivary testosterone in the sexes is indeed variable in each sex, and there is hardly any overlap between the sexes: Since testosterone prompts the development of secondary sex traits, including behavior, it’s the binary nature of sex that produce an almost nonoverlapping distribution of hormones. But one should not imply, as Fuentes does, that variation of hormone levels in each sex means that the sexes themselves are non-binary.
I don’t want to go on much longer, but I’ll add that Fuentes conflates sex and gender several times, and uses familiar tropes to dispel the binary, like the existence of hermaphroditic earthworms, which of course produce only two types of gametes, but in one body. He even shows a photo of a bluehead wrasse, which, like the clownfish (but in the other direction), changes sex in social groups (the head of a group of females is male, but if he dies a female changes sex and becomes the alpha-fish). And like the clownfish, this doesn’t dispel the sex binary because again, there are only two forms, one producing sperm and one producing eggs. Nobody ever claimed that a biological female can gametically transform into a biological male or vice versa. As always, there are only two reproductive systems, classified by their type of gamete. Neither of these animals produces a third type of gamete.
At the end, Fuentes reprises his error of saying that variation within sexes dispels any notion of a sex binary, and even lapses into philosophisizing:
I love the “why and how humans are in the world.” It’s totally meaningless! But wait! There’s more:
. . . last night, I was flabbergasted to read in the table of contents of the latest issue of Natural History, ‘Sex is a Spectrum: Why the binary view is problematic.”
That rumbling you just heard was SJG [Stephen Jay Gould] and his biologist forebears from this magazine spinning in their graves. Or so I infer.
OK, I am not a biologist and wouldn’t even try to play one on TV, and so wouldn’t claim the credentials or background to properly critique this. But I do have to wonder at the author’s writing in pretzel knots to avoid, for example, using the term “women” (preferred: “Humans with uteri” [p. 23]), or writing things I find hard to swallow (“the number of mating types (often called “sexes”) per kind of species…[is] two and sometimes three in most animals…”). I’d really like to know the animals that have three sexes (and what the third kind is called, and who it mates with).
h/t: Alex, Robert
I’m surprised this fool is still published and that he hasn’t sunk into the obscurity he so richly deserves.
The world is not short of mind slowing idiocy and (in his case) bad actors.
In the past decade I’m less likely to forgive stupidity when I realize it is rarely ignorance but rather maliciousness and bad faith.
D.A.
NYC
Since he considers that definition [of sex] to be harmful to people who don’t identify as either male or female, he presumably also considers the definition of “stupid” to be harmful to people who don’t identify as stupid. Wow, that’s stupid.
“I am patient with stupidity, but not with those who are proud of it.”
— Edith Sitwell
I find this quotation comes to mind quite often these days.
I almost wonder if some people who reject the sex binary are somehow psychologically motivated by metaphysical dislike of the cause their own existence.
Descartes famously said, “Cogito ergo sum.” I say more accurately, “Coitavant ergo sum.” And for the coitus to have been reproductively successful, each and every one of my ancestors going back hundreds of millions of years had to be quite unambiguously male or female.
I hope he writes a book.
Has been some time since I added to my “books that are wrong” collection.
Tom, he has written a book about it:
Agustín Fuentes: Sex Is a Spectrum: The Biological Limits of the Binary. Princeton University Press, May 6, 2025
Excellent!
Going right next to my “Worlds in Collision” by Velikovsky
My take on the excerpted “instability” claim made about women, is that it explains why most medical research of yesteryear was done using male subjects. On most outcome variables of interest, a random sample of a given number of male subjects will have smaller statistical variance than the same-size sample of women, simply because women vary through their monthly menstrual cycle in a way that men do not. To get statistically significant p-values on whatever hypothesis you’re testing, which you must do in order to get your paper published, it is quicker and more efficient to use only men because you won’t have to recruit as many subjects as you would if you enrolled both men and women. If you include only white upper-middle class men under 25 — college undergraduates of old — your variance will be almost as small as if you were using inbred rats. (“One rat is no rats. Two rats is a thousand rats.”)
This concession to research efficiency of course impaired the generalizability of research results to women patients, and their doctors, hoping to benefit from medical research. “Not my Department,” replied the researchers. “Give us more grant money if you want more inclusive samples because they will have to be larger, much larger if you want sub-group analysis looking for differential effect in women, not just including them in the over-all mean effect size.” (RCTs meeting these criteria involve many thousands of subjects in each arm and cost millions of Pharma dollars.)
Fuentes citing it here is incomprehensible without that background. It is written in a dated style that suggests he dug it up from some old journal archive and repurposed it for sex non-binary purposes.
(One of my colleagues was a nephrologist whose work involved measuring various things in urine. She told me she recruited only men in her studies because they have less trouble peeing in little bottles.)
Perhaps, and thanks, but “instability” isn’t the same thing as “higher variance”!
In this context I think it is. Twenty-eight premenopausal women drawn randomly from a population will be at different days in their menstrual cycle which, it is postulated, accounts for the greater variance in, say, urinary rhubarb excretion compared to men at one moment. (Rhubarb and porcelain are all-purpose joke words for obscure medical tests.). However that single-time data point is not a stable characteristic of the sample. If you tested those same women two weeks later, as you might need to do in some before-after study, they’d all be at opposite sides of their cycles…and cycle length itself is not constant between and even within women. So to the extent that instability of rhubarb excretion is caused by menstrual cycle, it contributes to the higher variance in the female sample. Each woman varies in rhubarb excretion from day to day, as well as varying from other women.
By contrast, a variable that is stable during the experimental period, such as height, would not have menstrual instability superimposed on the sample variance. Any difference in variance between male and female samples would be due to stable properties of the two populations, (plus sampling error of course.)
I was reading the medical binary section as a brief description of misogyny in medical practice. But I think your take is more likely what was intended.
Should also note, many of the studies done in the past were done by militaries. So they had what you describe, large groups of men under 25 years of age. And once completed, militaries of the time had little interest repeating the tests on women (who, in those days, were far fewer in number and not sent into combat).
Essentially no loss to follow up, 100% adherence to treatment, and big numbers easily “recruited” made for some very clean results.
I don’t understand the huge focus on people who have gender dysphoria. There are other mental conditions in which people have misguided views about their condition, and these are not given the unquestioned support of intelligent people. Body dysmorphic disorder is often treated successfully with CBT (at least that’s how a friend of ours’ was handled). We should treat gender dyphoria similarly rather than validating the individual’s delusion.
But delusions of a religious nature are explicitly excluded by the DSM. And attempting to treat sexual non-normativity is illegal in many contexts. And “trans” is both of these.
I think that it helps to know something of the history of “gender medicine.” It began with early surgical “sex changes” in the 1930s; trans activists (including some very wealthy ones) got involved in the late 20th century, and more or less controlled the direction the research took.
Here’s an interview Peter Boghossian did with Mia Hughes in which she gives a brief overview of this history. Spoiler: treatment for what we now call gender dysphoria was never evidence-based. As PB says, “there is no there there.”
Hughes’s rundown is from 2:35 – 30:30:
https://youtu.be/6XFuOJX4zRE?si=Fxsd9UodMQjDXLgG
The DSM-V defines “delusion” as “a false belief based on incorrect inference about external reality that is firmly held despite what almost everyone else believes and despite what constitutes incontrovertible and obvious proof or evidence to the contrary.” (Diagnostic and Statistical Manual of Mental Disorders [DSM-5]. 5th ed. Arlington, VA: American Psychiatric Association, 2013. p. 819)
The core characteristic of transsexuality is the desire to be(come) a member of the opposite sex and to be socially accepted as such. A desire is not a belief—neither a true nor a false one—, so it cannot be a delusion either. There may be, and in fact are transsexuals who do believe that they really are members of the opposite sex, and their belief may amount to a delusion; but if transsexuality is basically defined in terms of a desire (or wish), then there isn’t anything delusional about it as such.
Here’s a definition from the pre-woke era:
“[Transsexualism] denotes the intense and often obsessive desire to change the entire sexual status including the anatomical structure. While the male transvestite enacts the role of a woman, the transsexualist wants to be one and function as one, wishing to assume as many of her characteristics as possible, physical, mental and sexual.”
(Benjamin, Harry. “Transsexualism and Transvestism as Psycho-Somatic and Somato-Psychic Syndromes.” American Journal of Psychotherapy 8 (1954): 219–230. p. 220)
IANA clinical psychologist, but if someone thoroughly believes they are Napoleon then they are almost certainly DSM-V delusional. And have you looked for the DSM section that explicitly excludes religious beliefs? For example, consider the people who thoroughly believe that the Holy Spirit has given them the spiritual gift of interpretation of tongues (i.e. of gibberish)? Visit your local Pentecostal or Full Gospel church for a live demonstration.
I hope Fuentes does not develop a stable relationship with NH magazine. And if he does, I must then hope that he quickly wears out his welcome before he sullies its reputation, as he did for Scientific American.
What our host wrote is excellent: lucid writing supported by both theory and observations of sex differences (which are continuous and variable) in the context of sex (which is binary). Fuentes should be ashamed of his pathetic grasp of biology.
I fear this isn’t effective in public debate because Fuentes and those who think like him are pursuing a political project not a biological project. Arguing that he’s wrong on the biology of genderism doesn’t catch fire because so many of Fuentes’ readers are more interested in the politics of genderism.
A few days ago Kathleen Stock broke out a parallel line of argument (not a replacement): just call Fuentes a moron (actually “MORON” in the original tweet). Because what he’s arguing is moronic. And because, while Fuentes obviously doesn’t care if he mangles the biology, he does mos def care not to appear moronic because his stature as a Princeton Public Intellectual depends on his readers (and students and university administrators) believing him to be almost always the smartest guy in the room.
The money quote from Stock:
“I see so many people on [twitter] trying to shame the likes of [Fuentes]. It is hopeless. These people are utterly convinced of their moral rectitude, they automatically take disagreement as a sign of the limited mindset of their opposition. We should forget all that, and hit them where it hurts: in the ego. THESE PEOPLE ARE JUST A BIT THICK. They are promoted way above their station, have blustered through on their accents, educations, and connections, and now the tide is going out, we can truly see who is naked. Let’s learn from this, and never trust their so-called expertise on any other matter again.”
Call them stupid. Or “stupid as balls”, as someone wrote while quote tweeting Dr. Stock.
[edit to add the link to Kathleen Stock’s long-form tweet]
https://x.com/Docstockk/status/1917165815339589823
I get it but there is a bit of snark in what I wrote. And I am appealing not to Fuentes or his allies, who are hopeless, but to those on the fence.
Just like writing Trump IS STUPID over and over again is not going to change the minds of people. My post above is far stronger than I could put in an op-ed in a newspaper, for instance.
Yes I appreciate that. I didn’t mean my comment as criticism. I think what you’ve written is excellent and necessary. I think Stock might say that calling Fuentes a moron is a good addition because Fuentes depends on being seen as intelligent, and his readers who might be on the fence haven’t been told what a moron he really is.
My impression after having followed Dr. Novella and this site for several years now is that the disconnect is deeper than most realize.
Otherwise how could two knowledgeable and excellent thinkers look at and cite the same evidence and reach opposite conclusions?
My observations (apologies for excess brevity and any errors are mine as doing this from memory):
To our host, a theory is only as useful as it is broadly applicable. The simpler, clearer, and more broadly applicable the better. As such, gamete size wins. Everything else is obscurantism. Also, sex is a trait only, it says nothing about the person, their worth, value, or existence as all should be treated with dignity and respect. An individual can have one or both sized gamete anatomy (so male and female gametes) but is still only a trait (like straight hair, curly, some of both, or bald).
To Dr. Novella, human exceptionalism is key. So any definition that is not flexible enough to be comfortably applied to all human patients needs to be expanded. His focus his individual patients and while broad categories/definitions can be informative, the individual human takes precedence. Focusing on only one aspect (gamete size) is overly reductive and restrictive when dealing with individual people.
I posted a similar comparison on his site recently and his replies centered on the impossibility of agreement when core goals are so far apart, and why so much concern over surgeries in kids.
I just answered I was attempting to sort the disconnect.
My goal is the same with this post and can only hope I was reasonably accurate on both sides.
I have the impression that Fuentes would only accept that there is a sex binary if all men were taller than all women.
I don’t have this impression. I mean there is no overlap in reproductive organs and anatomy of healthy males and females.
This is all about politics. Sex is a category in law. By redefining it you may be able to create a new legal reality (a new distribution of rights and duties) without having to change any laws (which would require legislative majorities).
The main point of all this is to confect a new definition of sex according to which you can change your sex, because then transwomen literally are women.
If he actually wrote that last “males” then he doesn’t understand what he’s saying, just as I don’t. I expect it was supposed to be “females.” Even he did write “females” it is still a silly argument. It would be like saying a penis is not a male organ because females have a clitoris. Size can matter, and testosterone level can matter too.
“I’d really like to know the animals that have three sexes (and what the third kind is called, and who it mates with).”
If you think that is wacky, PZ Meyers believes horses have SEVEN sexes!
But we all know about PZ’s weird relationship about the animal kingdom.
Reference, please!
Great post! Typos:
“before social justice ideology arose, and a reognition”
“with 3G males usually having much higher levels than 3G males”
Re: the Figure 1 on male & female testosterone levels, as measured by radioimmunassay (RIA) on salivary testosterone. I think it’s even more binary than that. Carole Hooven’s book T: The Story of Testosterone has a detailed review of various methods for measuring testosterone and how some of them are less accurate, especially on the lower female end. The sex-is-a-spectrum folks like to cite the less accurate methods & argue for a continuum, but Hooven says:
“The least expensive and most common method is called radioimmunoassay (RIAs), which can measure T in saliva or blood. But you get what you pay for. RIA has enough problems that we stopped using it to measure female T levels years ago in our Reproductive Ecology lab at Harvard (and many other research labs have done the same). First, different kinds of test kits can yield vastly different results. And second, in women, immunoassay tends to pick up other, weaker androgens that are similar in structure but don’t have the potency of testosterone in tissues like muscle. This ‘cross reactivity’ with other steroids can drastically inflate women’s reported T levels! This isn’t a problem in men because their T levels are so high in relation to weaker androgens that the cross-reactivity makes no difference.
As a recent study examining the accuracy of T measurements based on RIA concluded: ‘This tendency to inflate very low concentrations of testosterone creates a substantial impediment to accurately assessing women’s testosterone.’ Another study put its limitations more bluntly: ‘Are assays that miss target values by 200-500% meaningful? Guessing would be more accurate and additionally could provide cheaper and faster testosterone results for females.'” (p. 111)
p. 112:
“So what does the evidence from more reliable measurement methods show? Mass spectrometry (‘mass spec’) is the gold standard of T measurement and is increasingly used by clinical and behavioral researchers in endocrinology. It is the only method used by anti-doping agencies, which require a high level of accuracy for both males and females.”
[Hooven reviews the “most recent, comprehensive, and rigorous study on adult T levels” by David Handelsman. She concludes (p. 113):
‘We already saw a “bimodal” distribution in the first chapter — the distribution of adult height. A bimodel distribution has two peaks. And in the case of height, the male and female distributions look like two mountains with wide, overlapping bases. In other words, male and female heights significantly overlap, since some men are shorter than many women and some women are taller than many men. But with testosterone levels, that bimodal distribution has a “wide and complete separation,” like two mountains separated by a vast plain, as you can see in the figure below. In other words: a binary.”
(p. 113, emphasis original)
Boom! No wonder they canceled her.
(the Figure, “Blood T levels in healthy young men and women”, has female T from ~5-~80 ng/dh, then male T from ~200-~1000 ng/dL — nanograms per deciliter)
PS: This is the study Carole Hooven is citing:
David J. Handelsman, Angelica L. Hirschberg, Stephane Bermon (2018). “Circulating Testosterone as the Hormonal Basis of Sex Differences in Athletic Performance.” Endocrine Reviews, 39(5): 803-829. October 2018. DOI: http://dx.doi.org/10.1210/er.2018-00020
Revisit the Magisteria argument… there’s the Magisteria of Science and the Magisteria of Ideology.
If they were truly separate there would be no debate about sex as biology and sex as a social construct. But some people find it rewards them to blur the Magisteria.
As we here expect (a good thing) Jerry has laid it out clear as day once again.
Sex on a spectrum like a kabarb is what Fuentes wants us to believe is flatulence, smells funny and then dissipates.
Sex is binary. The rest is a party. 😜
Did someone say PARTY! Ok! invite Ronan the sea lion to kick it all off.
I don’t trust anyone who uses the word “problematic.” Enough said.