Yet another failed and ideologically-driven attempt to show that there is no sex binary in humans

May 13, 2022 • 10:30 am

The first two responses I had to the title of this article by Princeton anthropologist Agustín Fuentes in Sapiens (an anthropology magazine) were, “No, biological science does not reject the sex binary, but I guess you do”; and “we don’t determine what’s true or false based on what’s good for humanity.” Click to read:

You may remember Agustín Fuentes from a previous dustup in which he wrote an article in Science accusing Darwin (who was an abolitionist) of racism, and then got a lot of responses noting that while Darwin did make statements that would be considered racist, he was remarkably liberal for a man of his position in his time. As I wrote in part of my response:

But, despite Fuentes’ admission of Darwin’s strong abolitionism, he seems to forget that Darwin was a man of his time, not of our time. Is it fair to judge Darwin against an enlightened modern liberal? I don’t think so: the proper judgment is to see whether Darwin was palpably morally worse than most other Victorian Englishmen.  And I don’t think he was. I’ll explain a bit more below, but I have a very hard time thinking of someone of Darwin’s stature in Europe who was much better than he on the issue of women, or, for that matter, slavery. (Read Marx and Engels on the Irish if you want real bigotry.) Yes, Darwin saw some South Americans as “savages”, but he also perceived their common humanity with us, and his theory affirmed our common ancestry. And yes, he saw women as the inferior sex; but how many Victorian men were far more enlightened than he?

Frankly, I’m tired of people who say things like “Darwin was bad because he should have known and done better.” Neither he nor his contemporaries did or could have: morality evolves, and in 150 years our own generation may be seen as just as morally deficient as was Darwin. After all, we eat meat, and in the future we may learn more about the suffering of animals in ways that would brand us moderns as horrible barbarians. The judgment of celebrating Darwin should rest on a). “is he being celebrated for the good things he did?” (answer: yes), and b). “did the good he did in his life outweigh the bad?” (answer: also yes).

I’d wager that Fuentes himself, if he were a white upper-class man in Darwin’s time, would have been more racist than Darwin, though of course that’s mere speculation. At any rate, other people responded critically to Fuentes’ Darwin-dissing, and you can see a selection of critiques at this link.

But Fuentes has moved on to going after other aspects of biology, and in the article above he commits what I see as the cardinal sin of woke scientists who should know better: denying that, in humans at least, sex is a binary. (It also happens to be a binary in most other animals.)  The biological distinction between the sexes, which I’ve written about too many times to count, is this: members of the male sex make small, mobile gametes—sperm.  Members of the female sex make large, immobile gametes—eggs.

This has nothing to do with genitalia or other morphological characteristics. And using that (accepted) definition creates an effective binary in humans: if you can make sperm you’re male, if you can make eggs you’re female. Yes, there are some who are sterile, or who lack testes or ovaries, but those are not members of some “intermediate” sex: they are developmental anomalies, and they’re very rare. (Yes, their existence means that there are a few small blips on a chart of “frequency of sexes” with males at one end and females at the other, but for all practical purposes the plot is a bimodal one, i.e., showing a binary.) And yes, some people are postreproductive and have “outgrown” their ability to produce gametes. But there is no “sex” that doesn’t produce eggs or sperm. There are no individuals that produce intermediate forms of gametes who can be the basis of a third reproductive class of humans.

But for reasons that are purely political, people like Fuentes reject this binary, banging on about hermaphrodites, penises and labia that are not “normal”, hormone levels, fish that change sex, and so on, but let’s face it: in nearly all animals, biological sex, which is the way that “biological science” defines sex.

I really can’t bear to reproduce all Fuentes’s circumlocations and diversionary prose, but here’s a sample that ignores the sperm-egg dichotomy:

Of course, there are clear bodily differences in capacities to give birth and lactate, and ranges of patterns in the development and distribution of body size, strength, and myriad other processes. But such patterns are mostly overlapping, and only a few are distributed in clear or functional dichotomies. Numerous studies have found that the differences between adult men and women are overhyped and largely influenced by the dynamics of biology and culture. Humans are naturenurtural—a fusion of nature and nurture.

And forgive me if I give the slightly censored version of a biology friend’s reaction to that paragraph:

So like EGGS AND SPERM you dumb [redacted].
So why does Fuentes avoid the biological definition (and the resultant binary)? For political reasons, of course. His motivations are good—to reduce bias and bigotry—but you don’t do that by denying the truth.  That both demeans science and is not a good way to dispel bias.


Two quotes from Fuentes’s article:

Today a chorus of scientific-sounding claims about “blue and pink” brains, testosterone, and male primate aggression are offered up as natural explanations for masculine and feminine behavior, along with gaps in pay, jobs, political and economic leadership, and sexuality. In the political and legal realms, the belief that biology creates two types of humans is invoked in a range of attempts to mandate and enforce how humans should behave.

These assertions and beliefs are wrong. In addition, the commitment to a simple binary view creates a fictitious template for a “battle of the sexes” that manifests in miseducation about basic biology, the denigration of women’s rights, the justifications of incel and “men’s rights” violence, and the creation of anti-transgender laws.

Science points to a more accurate and hopeful way to understand the biology of sex. By recognizing the true diversity of the human experience, humanity can embrace an expansive and multifaceted way of envisioning and experiencing human nature. This evidence-based outlook is not only far more interesting than the simplistic and incorrect “tallywhacker versus no tallywhacker” perspective, but also more conducive to respect and flourishing.

. . . and his not-even-wrong denial of biological sex:

The data-driven bottom line is that “man/woman” and “masculine/feminine” are neither biological terms nor rooted exclusively in biology. The lack of an explicit binary is especially evident in humans given the complex neurobiologieslife histories, and morphological dynamics in our species. There are many successful, biologically diverse ways to be human, and millions of people embody this diversity. Growing up human means growing up in a world of varying gender expectations, body types, reproductive options, family structures, and sexual orientations.

So, instead of listening to people who are misogynistic, sexist, or homo/transphobic; incels; or politicians who base their ideologies on a biological sex binary and myths about its evolution, we can and should be open to a serious understanding of biology and its better options for human flourishing. The simple male/female binary does not effectively express the normal range of being human. Understanding this and incorporating it into our education, lives, and laws offers better possibilities, greater equity, and more joy for human society.

I must say that I find this kind of “twisting the facts” to be particularly pernicious, especially from those who we expect would know something about biology:

There is an explicit gamete-based binary, which is well defined and, yes, accepted by “biological science”. Fuentes doesn’t like it because he thinks that it creates misogyny, transphobia, and other forms of bigotry. It doesn’t. It’s just a definition that accurately mirrors the situation in Homo sapiens—and most animals. But the truth is the truth, whether or not people like Fuentes likes it. It is bigotry, not science, that creates transphobia and misogyny.

Although Feynman’s famous statement below referred to the Challenger disaster, the last bit might be applied to those who try to deny biological reality in the service of ideology.

For a successful technology, reality must take precedence over public relations, for Nature cannot be fooled.

And for those who like audiovisual, here’s a tweet (suggested by a reader in the comments below):

UPDATE: Reader Bill sent me a comment with a figure he made, but couldn’t embed the figure, so I’m putting both up here as an addendum:

I cannot believe that people continue to claim, Fuentes does, that since characteristics of two groups overlap when examined singularly this necessarily means that the two groups overlap. One has to consider the covariation of the characters. Consider the graph below. The groups are distinct, one might say binary, yet there is considerable overlap in the two characters when considered singularly (project each onto their respective axes).

41 thoughts on “Yet another failed and ideologically-driven attempt to show that there is no sex binary in humans

  1. Attempts to fool nature, on behalf of egotism and/or political propaganda, are an old story, Modern examples include such classics as the practical results of Michurinist (Lysenkoist) agronomy, Hitler’s brilliant tactical thrust into Stalingrad, and the logistics of Putin’s recent brilliant campaign against Kiev. Along with all the human tragedy involved, there is a sense in which enterprises of this sort end up taking care of themselves—like Icarus’ little problem with the wax of his artificial wings.

  2. This is a good, sometimes political, twitter thread from someone who tweets about the sex binary….

    This essay is by transman Chase Strangio, well-known and controversial ACLU lawyer who wanted to ban Abigail Shrier’s book….actually destroy it. He does not “believe” there is such a thing as a male body….

    And finally, a gender that I can identify with….”Cake Gender”….and yes, I do believe it’s for real.

  3. At level of types of gametes, it certainly seems binary: there are only two (egg and sperm). There is no third gamete.

    Would that point be dismissed by these “woke” biologists as too reductive?

    1. Well, some fishes can actually change sex either way (and hence gamete production), and slugs are male and female simultaneously. However, none of that is found in mammals, and hence humans. I think the complex, highly specialised, structure of eutherian reproductive organs may have something to do with that (not being able to change sex).
      Still in all these cases we are talking about a dichotomy of small mobile or large less mobile gametes.
      For an undifferentiated sex, ‘intermediate gametes’ you’ll have to go back to fungi. No animals do, but fungi do.
      Are fungi the Woke’s paradise?

  4. only a few are distributed in clear or functional dichotomies.

    Correct! Biological sex is one of those few.

    Is this really so hard? One can be liberal and socially conscious without giving up this point.

    1. Most biological traits have a smooth distribution, though a few are binary.
    2. Many traits society treats as male/female binary, aren’t. Examples are things like aggression, color preference, job preference, parenting desire, strength, coordination, endurance, etc., etc.
    3. #2 Causes all sorts of social problems and discrimination. Which we should oppose and seek to eliminate.
    4. But biological sex is binary.
    5. #4 also creates social problems and discrimination, because biological sex is often used as a proxy for the traits listed in #2. We should also oppose and seek to eliminate that discrimination.
    6. We accomplish #5 by teaching/socializing people to stop using binary sex as a proxy for nonbinary traits. #5 is not best achieved by pretending sex is nonbinary.

    ISTM folks like Dr. Fuentes are using a “little people” strategy – not trusting that the public can handle the nuance needed to arrive at the correct conclusion. Personally I’m a lot more optimistic. The people who can figure out that “girl” /= “slow, innumerate, likes pink” are obviously much more prevalent than the people who can’t figure that out, even if the latter are sometimes more vocal. I say ‘obviously’ because people /= only men.

    1. In the Brussels ‘St Pieters Hospitaal’ (Hopital St Pierre) where I did quite a bit of my training, the file-covers for boys were pink and light blue for the girls. I think that in East Asian cultures red is male and blue female (like in ‘the rest of the World’ red is the colour of socialism, and blue for the more right wing parties, note here that many ‘right wing’ parties in Europe would be considered centrist or even moderately left wing in the US). I’ve always wondered where this association of girls with pink came from. I suspect it’s quite recent.
      And yes, biological sex is a binary (especially in mammals), and much of behaviour is too, albeit not as clear cut. In behaviour you do find intermediates, a spectrum if you want, but you still have 2 clear ‘peaks’.
      In that context I’m always struck by how ‘traditionally considered male’ -and basically misogynistic- the conduct of trans-‘female’ activists so often is.

  5. Rather than comment on the tiresome idiocy of “the sex binary is a social construct,” I have an evolutionary biology question: Why is the average man significantly stronger than the average woman, especially in terms of upper-body strength? Is it because:

    a) The human body can be optimized for successful pregnancy or physical strength, but not both;

    b) Men compete for access to female reproductive capacity, which is the rate-limiting factor in reproduction. Strength helps in this competition, resulting in higher selective pressure on men to be strong;

    c) Both of the above;

    d) Something else I haven’t thought of?

    1. I wouldn’t be sure either a or b is correct. We know the fact of, we don’t necessarily know the evolutionary reason why. Could be sexual selection or intraspecies selection, like your b. Could be natural selection or interspecies factors, like your a. Could be a Gould spandrel. Could be a sloppy evolutionary “mistake” – maybe the reason testosterone goes into the male blood stream (not needed, produces all those physique changes) and not just the testes (where it is needed) is simply because there was little evolutionary pressure to not let that happen. No adaptive pressure to produce or maintain a “non-leaky vessel” for testosterone. I suppose – but seems very unlikely – it could even be a product of some long-past genetic drift in apes. And of course it could be something we haven’t thought of.

      I would not link the sex vs. gender argument to the “why” of human sex dichotomy. Seems mostly irrelevant and a distraction. It’s sufficient to point out that the existence of testosterone-fueled changes does not in any way dictate what bathroom we let people use, or what we call them, or what is acceptable social dress, or even how society arranges intramural sports. What nature provides does not dictate morals and ethics or how humans organize their activities.

      Fuentes is trying to imply that nonbinary sex => nonbinary rights. Which is the is/ought fallacy on steroids. Both figuratively and literally – ha ha!! 🙂

    2. Men are the soldiers of the species/human reproductive groups. It’s men because they are more expendable than women, as sperm is plentiful and wombs are a rare resource.

      1. Which is why female fertility must be regulated by men who die to preserve the resource and ensure its fecundity..

      2. That is group selection thinking. If a trait makes it more likely I personally go off and die before having kids, but my death helps the group survive (i.e. by my common resource death saving the group’s rare resource females), then that trait should die out over generations. Only if the group is mostly siblings, nieces, nephews, etc. could that be adaptive, according to Darwin.

        1. As George Patton supposedly said, “I don’t want a man who is willing to die for his country. I want men who are willing to make the other sumbitch die for his country.” Winning is not maladaptive if done decisively and efficiently. It’s only when an army loses that it is massacred, and that is definitely maladaptive. A victorious army rarely suffers more than 10% casualties. Most armies will break and run, and be slaughtered by pursuing cavalry or cut off in pincer movements before decimation results from direct combat.
          The infantry battles of the First World War were maladaptive by your undoubtedly correct analysis and are still studied from that standpoint.

          Granted there is individual combat where men who are not related to each other hold out and die against overwhelming odds, such as the Ukrainian soldiers defending civilians trapped in the Azovstal steel plant in Mariupol. (But even they seem to have prevailed and not died.)
          The whole indoctrination of a modern army is to see your fellow squad mates as your kin, brothers even. This is necessary because, as you say, people won’t readily risk their lives for people they aren’t related to but national purpose demands they do. Many of the Medals of Honor awarded to American GIs in Vietnam were to soldiers who threw themselves on grenades that had been tossed into their bunkers. It’s startling to see how often this appears in the citations. Yes, it would be the guy closest, who was going to surely die anyway, but still….

        2. I didn’t only mean soldiers for interhuman conflict. Hunting was a male occupation that needed strength and in the mid and late pleistocene at least was very dangerous, so this is another area where physical male strength combined with male expendability was needed (that is similar but not identical to your hypothesis a).
          So you think warfare between neighboring bands of humans (wasn’t that the rule rater than the exception in history?) is just intermale physical competition for females, as seen in rape and invader y-chromosome dominance after migration? Extant hunter gathers are mostly monogamous, they are also often closely related (within a small roving band), so I don’t see why group selection needs to be discounted a priori. Polygyny and huge intermale variance in reproduction is more of a thing in agricultural/herder societies with huge wealth differentials. Then again, some agricultural societies are organized in highy endogamous tribes that fight each other.

          1. Hunting was a male occupation that needed strength and in the mid and late pleistocene at least was very dangerous, so this is another area where physical male strength combined with male expendability was needed

            That’s a very common hypothesis, yes. But AFAIK nobody is really sure it’s true. It could be putting the cart before the horse – maybe the different physiology serves some completely different purpose (or no purpose at all), but because males have it, they socially gravitate towards hunting. It could be, as drosphilist points out, a sexual selection trait not a survival trait. Or it could be, as I point out, just an unintended consequence of the need to make sperm. It could even have a negative adaptational value, and it is simply the case that evolving a fix for it is either evolutionarily impossible (think giraffe laryngial nerve) just more costly than the problem. After all, men can have babies pretty much until they die; it is arguably maladaptive for them to evolve a sex-related trait that makes them die earlier.

            1. Yes, very difficult to pinpoint the primary selection driver here, and whether if it was selection and not pleiotropy or something similar. Male strength is old in hominins, and the very dangerous type of hunting (megafauna) was a relatively late development jn human history, so this idea of mine is probably not relevant/hunting must a secondary phenomenon. Group rivalries seem to be universal in humans, though (also extant in Pan troglodytes), and so are psychological mechanisms like ingroup/outgroup biases. If the neighboring band wants to steal your winter provisions or wants to empty your hazel trees or kidnap a woman, your genes will be helped, not hindered if your band is able to fight them off, even if you die but some of your brothers or cousins or your uncle and little lister survive. A lot of fighting is avoided by ritualized showing off/shouting matches, but displays of strength and resolve are needed even for that.

              1. PS: by “a woman”, I meant a woman that had joined your band and is not closely related. As far as I know, female exogamy (i e it was mostly the women who left the group upon sexual maturity) was the rule rather than the exception in human prehistory. That includes one Neandertal case study on the genetically well preserved El Sidron family group (, and is also seen in Pan troglodytes.

      3. But does evolution really work at this “group” level?

        I would have thought the answer would be more like “genes for increased upper-body strength are more likely to be replicated when expressed in male bodies than in female ones”.

        Meaning, the gene doesn’t give a whit about how successful the species is. It could only possibly “care” about whether the effects is has on the body it resides in can promote its own replication.

        I think your answer explains WHY genes for increased strength may be more likely have more copies made (through successful reproduction) in male bodies than female, but the “gene’s eye view” provides and even more fundamental level of explanation. At least that’s what I got out of reading The Selfish Gene and The Extended Phenotype.

  6. Even his numbers give only a .2% ((280,000/140,000,000)*100) rate of what could be considered abnormal sexual expression or genetic or chromosomal abnormality or whatever
    Since he seems to lump them all together. (These numbers seem very conveniently round(ed)). Would this percentage include gay? Maybe. Trans, cis, non-binary? Again maybe. He makes many insupportable assumptions and statements of “fact” apparently because if they were true they’d support what he wants to be true.

  7. One might just dismiss this article as yet another example of the politicization of science but it’s more damaging than that: it gives the woke (and media allies) a citation in a peer-reviewed journal to use in their arguments. For them, one such article is a “slam dunk” for their side, not understanding that science proceeds by a large literature that evolves over time.

  8. Is the author really being honest here? He seems to know exactly where to dissemble in order to make his spurious claim. If he knows exactly where to zig instead of zag, how can he not be conscious of the fallacy of his argument? I like to think that he is simply wrong, but the way he navigates around the problems in his argument suggests otherwise.

    1. Nicely put, Norman.

      I understand that people with genuine intersex/DSD conditions are sick and tired of being misrepresented by gender identity theory activists to buttress their woeful arguments about sex in humans.

    2. This is where an idea like post-modernism, which (deservedly) gets a lot of flack, may have a grain of insight in that it sees human discourse, even in academic circles, as an exercise in power and not in obtaining “objective” knowledge. The author is not seeking to make a rational argument, or even right a wrong. He may simply be seeking to take advantage of this wave of wokeness, and use it to promote himself within the power structure that he swims in. Meaning, he knows exactly when to use reason, and also when to strategically abandon it to promote his goals.

      1. Zach Elliott is not a biologist either but he has a better grasp of biology than Dr Fuentes.

  9. Yes, there are a huge number of ways to be a woman or a man, the traditional sex roles that we are taught about are very limiting and oppressive. No, this does not mean that humans are not sexually binary or that binary sex doesn’t exist in other species. One of the thing that bothers me terribly about all this is the idea that men and women who do not fit the traditional patterns are actually not actually men or women. I’ve worked with kids for decades and have always told them that they should value their own thoughts, feelings, interests, etc., that no one has a right to intimidate or bully them, and that they have every right to be proud of themselves for being unique boys or girls. The new ideology seems to be based on old and tired steryotypes, and while some say it is liberating, I don’t think it is.

  10. A bit off topic but since you brought it up:

    I’d wager that Fuentes himself, if he were a white upper-class man in Darwin’s time,

    This supposition doesn’t really make sense; it’s like asking “if <a href="""The Cube were cylindrical, would it roll when pushed?” If it were cylindrical it wouldn’t be The Cube. If a white upper-class man were born in Darwin’s time, it wouldn’t be Fuentes. The idea that a particular person could have been born to different parents in a different time and raised very differently, is a vestige of a dualist viewpoint on personal identity.

    1. But I think that the very point. The 1800’s Fuentes would probably be far more racist and misogynist than 2000’s Fuentes. We are who we are in large part bc of our cultural upbringing.

  11. I had thought Marx and Engels properly sympathetic to the oppressed Irish peasantry. There was a change of heart regarding associations with the British working class as far as furthering the good interests of both but I haven’t heard of the disparagement and bigotry you claim. Could I have a pointer to something I could read about it it please.

    1. “Bigotry” is a modern interpretation that takes a non-politically correct but probably largely factual description of cultural traits and of the role Irish immigrants (unwittingly) played vis a vis English workers out of context. But that was PCC(E)’s point, that’s what the woke do, they would read Marx/Engels and be shocked, just like Darwin shocks them, even though were the progressives of their day.

      1. I would still like to read some of this supposed bigotry as the descriptions of the Irish and their culture and the suppression of their culture by the British, never giving them a chance to develop and improve wad 100% sympathetic such that I won’t believe they were bigoted against the Irish, interpretation issues or otherwise until I see it myself.
        I had a quick look and didn’t see anything.

  12. Robert Wright, in ‘The Moral Animal’ said Darwin used to lose sleep at night worrying about the bad treatment of slaves in South America.

    I read that 30 years or more ago but I think its correct.

  13. Surprised that the woke haven’t yet brought up trisexual slime molds or septasexual alveolates.

    1. They also haven’t figured out that fungi, which are more closely related to animals than plants are have a multiplicity of sexes. If they do figure that out they will go through the roof in an unscientific way, so shhhh,

  14. A recent WIRED article is headlined: “Science Is Redefining Motherhood. If Only Society Would Let It.” After relating insensitive treatment of a pregnant (um) person by “medical staff”, the author claims:

    And yet woman and mother are not, nor have they ever been, synonymous. In fact, neither term has any objective reality at all.

    What do you think? Is “science” doing the redefinition to which the headline refers? Or is it ideologues?

  15. The article itself even admitts to the binary template, then argues against it on more secondary and superficial notes. E.g: “Starting at the most basic level of animal biology, there are multitudes of ways to be female or male or both.”
    Yes, that is what biological sex is, the reproductive *function* a given organism coded to support (regardless of variations above or below it).

    The article almost pulls a hamstring in its effort trying to push the general understanding of biological sex into the more fuzzy, socially influences realm of ‘gender’, which understandably translates poorly to binary modes of course.
    Biology primarily deals with function, not essence, so the article travels into Strawman-Ville with mentions of sexed brains et al, which are where secondary sex-characteristics may show as opposed to the primary function a member of a species is coded to support (which again is how we define biological sex). And it rests on two forms of gametes, not three or four or five or six and a half but two.
    I do not agree with the ideological blank-slate’ian need to reshape the definition of biological sex just to make it more socially palatable for some people, where one is to regard much if not most as social constructs. The reality of biological sex, as it is, is in no way an enemy toward better understanding of our social roles or identities or preferences, so stop treating it like it is.

    Furthermore, if we look at a somewhat comparable analogy of code; binary code (for programming). It’s all 0’s and 1’s. Is it binary? Yes. Is 0100110 still binary? Yes.

  16. Opinion pieces like this are breathtaking in their intellectual dishonesty. They push a narrative that because variation exists withing the sexes, additional sexes besides male and female exist. Notice how they never fully spell out what they are trying to say: that congenital disorders of sex development are their own sexes. They never do this, ever, because they know how preposterous it sounds when told straight out. No, instead they parade these rare developmental anomalies as proof of a vast and amorphous ocean of biological variation that hides within its depths a third sex, and a fourth one.

    This same strategy is used in the opinion piece that appeared in Nature, of all places, in which the author writes that sex is so impossibly complicated to define that the surest way to ascertain a person’s sex is just to ask him.

    “So if the law requires that a person is male or female, should that sex be assigned by anatomy, hormones, cells or chromosomes, and what should be done if they clash? ‘My feeling is that since there is not one biological parameter that takes over every other parameter, at the end of the day, gender identity seems to be the most reasonable parameter,’ says Vilain. In other words, if you want to know whether someone is male or female, it may be best just to ask.”

    In all the world of unhinged anti-scientific gobbledygook, this has to be my favourite example. Just imagine it. A person with an education in science announces that he cannot determine an individual’s sex scientifically, so it’s better to just walk up to him and ask him what he thinks it is, and then record that as an objective finding.

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