Wednesday, October 13, 2021

The existence of intersex people illustrates how sex is biological and binary

Folk are intersex because of how their biology is within complex and varied manifestations of two sexes.

Participants at the third International Intersex Forum held in Malta, December 2013.

There is this rather tedious game that is sometimes played where the existence of intersex people is somehow taken to indicate that either sex is not biological or that sex is not binary.

Any suggestion along the former lines is easily dealt with: a person is intersex if they have a specific type of pattern of biological features. That is, in the words of the UN OHCHR (the UN Human Rights Office):
Intersex people are born with sex characteristics (including genitals, gonads and chromosome patterns) that do not fit typical binary notions of male or female bodies.
Those sex characteristics are, of course, biological. It is the biological structure of their body that makes someone intersex.

Use-referent confusion

The wording typical binary notions of male or female bodies is a genuflection towards sex as a socially constructed category. That categorisation within a language is a social act does not make the thing being referred to thereby socially constructed. To act as if it does is to confuse use of a term with the referent of the term.

This use-and-referent confusion, this confusion between category and object, is not a case of failing to distinguish between use (“I like eating cheese”) and mention (“'cheese' has six letters”), but it is similar level of logical error. That the practice has evolved of calling a particular set of dairy products cheese does not mean those dairy products are socially constructed by that act of categorising. However socially embedded cheese-making may be, such dairy products are created by a series of physical processes and have a physical existence not dependant on the categorising conventions of particular languages.

Both types of logical error come from the aboutness of language and thought; from us using language to speak, and categories to think, about other things.

Sex existed long before anyone was developing categories about sex. Sex continues in the biological world all around us, regardless of what categories we may choose to use, and how.

It’s all about the gametes

If your body is structured to produce small, self-moving (motile) gametes, you are male; regardless of whether any viable gametes are actually produced. If your body is structured to produce large, not self-moving (sessile) gametes, you are female. Also regardless of whether any viable gametes are actually produced. A gun does not stop being a gun by removing its firing pin or filling in the barrel.

At its base, sex is defined by reproductive function. Such a pattern of only two types of gametes means that sex is, at its base, in its biological function, binary.

If the evolutionary die were to be thrown to generate new genetic combinations, there had to be at least two gametes. If there were more than two gametes, that would greatly increase the difficulty in successfully reproducing. If there was going to be two gametes, one that was injected (so was small and self-moving) and one that received (so was large and not self-moving) also maximised the chance of successful reproduction. Hence, male and female gametes.

Given certain basic conditions, if a species reproduces through the combining of gametes (i.e. reproduces sexually) then having two types of gametes — small, self-moving (motile) gametes and large, not-self-moving (sessile) gametes — is the only evolutionary stable outcome. Hence, in our biosphere, sex is binary because there are only two types of gametes.

Thus, there is no third sex at the level of gametes. There are neuter forms of females in eusocial insects. In some species, an individual can change sex. But there are only two sexes in the sense of only being structured to produce one of two types of gametes. Some individuals partake of characteristics typical of both sexes. That does not make them a third sex.

While, in its base evolutionary function, sex is binary, the manifestations of the binary nature of sex in organisms can get quite complex. That sex is binary doesn’t mean that bodies are. In a way, that is probably the evolutionary point. A widely accepted hypothesis among biologists about why species adopt sexual reproduction via gametes is that it was an evolutionary adaptation to deal with pathogens. By sexually reproducing, the genetic die are being thrown again and again, giving sexually reproducing species a much better chance of having genetic lineages that could survive a particular pathogen.

In us Homo sapiens, as mammals, there is a set of characteristics that are specifically typical of the male-body structure and a set of characteristics that is specifically typical of the female-body structure. If you have some characteristics from both sets, you are intersex. But it is precisely the existence of these two sets of sex-typical biological characteristics that creates (1) the possibility of being intersex and (2) enables identification as intersex.

So, the existence of intersex people does not confound either the biological or the binary nature of sex. On the contrary, it refers to a set of people with various patterns of biological characteristics that can only be identified as falling within the set of intersex people because of the binary and biological nature of sex. Human bodies are bimodally distributed, but with sufficiently fuzzy boundaries that some folk are intersex, they overlap the distributions somewhat.

Evolutionary pressure

Arguments about, for instance, the concept of binary being binary — something is either perfectly binary or it is not binary — are ways of avoiding grappling with the biology. For biology has lots of fuzzy boundary concepts (e.g. species). Defining binary in a way that means nothing biological of any complexity is likely to meet it is not a proof that sex is not binary. The small self-moving gamete/large not-self-moving gamete difference is binary in the sense that counts in terms of reproductive function. Reproductive function that is subject to, and shaped by, evolutionary pressures.

It is that evolutionary pressure that makes, sex, in its base evolutionary function, binary and its physical manifestation in human bodies bimodally distributed. 

If there were actual hermaphrodites in a species with males and females, there would be grounds for calling them a third sex, as their bodies would be structured to produce both gametes. That would not, however, change the binary nature of sex in its evolutionary function.

The key confusion is failing to grasp that the binary nature of sex applies to its evolutionary function. If conjoining gametes is how reproduction happens, and there are only two sorts of gametes in play, then sex is binary. It is that simple.

This is not a claim that individual organisms cannot have a mixture of features. It is not even a claim that individual organisms cannot move across the boundary from one sex to another. It is also not a claim about animals conforming absolutely to to two, and only two, rigidly distinguished physical structures. It does not even preclude an organism producing both types of gametes, either sequentially or simultaneously.

The binary nature of sex is not defined from structures of bodies inwards. It arises from reproductive function outwards. As a biological process, reproduction has consequences for physical structures, but these can be quite complex and varied. A complexity and variance that does not in anyway change the binary nature of sex, though it does considerably complicate its expression in biological structures.

Animals have sex roles: the behavioural manifestation of sex. The manifestation of sex in a deeply cultural species is even more complex, hence gender: the cultural expression of sex. With gender we are in much more varied, and culturally evolved, territory.

In summary, there are only two sexes at the level of basic reproductive dynamics, defined by there being only two types of gametes. There is no third sex at the level of reproductive dynamics because there is no third type of gamete. Hence, sex is binary, however complex the manifestations in bodies of that underlying only-two-types-of-gametes pattern may be.

So, when folk say that sex is binary, what they should mean is that there are two types of gametes. And when folk say that sex is not binary, what they should mean is that the biological expression in actual bodies of the binary nature of sex is bimodal rather than binary. Though it is a clumsy and misleading way of doing so.

The rest is just tedious word games, with more than a dash of logical confusion.

[Previous version posted on Medium.]


  1. So long as we're playing tedious word games, you took a really long time to work your way up to the relatively simple concept of "bimodal", and you constructed some really impressive strawmen to knock down along the way. Including stating outright that sex is binary, before concluding that it is bimodal.

    There is a continuum of sexual characteristics in a complex interplay, and there are two big obvious peaks in their distribution. This is not a complicated concept, which you acknowledge.

    When intersex people talk about a "third sex", I suspect it's more that they recognise that there's "male", and "female", and their third sex is "not entirely either".

    And that's the thing: as you say, we are a sexually dimorphic species. Moderately so, as things go. More than gibbons, much, much less so than anglerfish. And yet, while the default form is female for humans (that is, there are specific genes on the Y chromosome which trigger male development, and when those are knocked out, then the fetus develops as female even when XY), it still requires female hormones to complete development into the adult female phenotype. So even with the "default development", it requires an active biological effort to pick one side or the other. Indeed, there is an entire village in the Dominican republic with a common mutation where many children are phenotypically female up to the point of adolescence, at which point they literally grow penises and develop into males.

    When you say "If your body is structured to produce large, not self-moving (sessile) gametes, you are female." ... what about people with Androgen Insensitivity? They are physically built according to the phenotype typical of those who produce sessile gametes. And yet they have the chromosomal makeup of those who produce motile gametes. In the binary model, they must be male or female. Go on then, you're so clever: which are they? What about Kleinfelter Syndrome? The definition of a female is that they have two X chromosomes. The definition of a male is that they have a Y chromosome. Kleinfelter folk have both. Then there's Turner's Syndrome, who are X-, and have "gonadal streaks" rather than ovaries or testes. They don't produce any gametes. Male, Female, neither?

    Let's even take it outside the phylum: "There is no third sex at the level of reproductive dynamics because there is no third type of gamete." OK, then, explain drone bees. In terms of how their gametes are constructed, they are female, but they are not structured to produce gametes at all. Sometimes, gametes aren't the whole story.

    I'm not going to say that there is nobody who denies the bimodal distribution of sexes in humans, because this is the internet, and, well, QAnon exists proving that there are people who will believe anything. But nobody who knows anything about Intersex people denies that humans are strongly bimodal in terms of sexual characteristics. "Binary" is, as you say, right in some senses, wrong in some senses, and not even wrong in some senses. Which is why Intersex people, who have so many mechanisms for being intersex, identify with each other. Because they see the two modes on the distribution, and identify with each other as all sitting somewhere in between those peaks, neither one nor t'other.

    But still, when you finish with "tedious word games, with more than a dash of logical confusion.", I'm wondering how much of that is projection.

    1. You take a remarkably long time to not cover anything that was not already in the post. Drone bees are just an extreme example of eusocial insect neuters. I did not mention chromosomes. That there was more to sex than gametes is covered at length, but without gametes there is no sex. (There is also no ageing, but that is a whole different matter.) I already covered moves across sexes. In a world where people with penises are declared to be women in every way that counts, yes, these things do have to be spelt out.

    2. I prefer to think of it as taking less time to cover the same ground but come to the same answer yet the opposite conclusion.

      Do you think you're succeeding in convincing the people your bubble consists of that you're being virtuous in claiming that "transpeople aren't who they say they are because biology". (Therefore... what, exactly? If you're going to be trans-exclusionary, come out and just say they're mentally ill and need treatment. You know, just like you would have had said about you within your own lifetime.)

      You think intersex and transfolk don't understand biology?

      All you've said, all I've said, sum up as "Sex is, when you look at it, more complicated than you think it is, no matter how complicated you think it is."

    3. So, I am not who I say I am but transpeople are who they say they are? You are not listening to yourself. Nor do I find the need to be sneeringly abusive about people. "Transexclusionary" is just a bullshit way of saying female is a feeling. Female is biology. A trans woman is not actually a biological woman. That is why the requirement for hormones and surgery.

  2. > So, I am not who I say I am but transpeople are who they say they are?

    What? I have literally no idea where that is coming from or what you're trying to say there. Except if you're saying that you're not playing to the TER choir, because you really are.

    > Nor do I find the need to be sneeringly abusive about people.

    Show your article to a transperson and ask them what they think of that statement.

    > A trans woman is not actually a biological woman.

    1) Defining "biological woman" is harder than most people think.
    2) "woman" includes aspects of "female" and of "feminine". There is no such thing as "a feminine" in the same way as "a female". Insofar as "woman" is a social construct, they are women. And insofar as you are bending over backwards to pretend that they don't understand how biology works
    3) You seem to have argued yourself into the corner of people who are calling transness a mental illness at best, an active predatory perversion more likely. You know we're not so far from when homosexuality was treated in exactly that way, right?