Yesterday I recounted my short hunt for the oldest formal definition of the sexes using gametes (e.g., males are the group that produces small, motile gametes and females are the group producing large, immobile gametes). I, or rather MIT professor Alex Byrne, came up with a quote from Chicago geneticist Horatio Hackett Newman. As Alex says, “This is from his 1924 Outlines of General Zoology. [p. 330].”
I continued looking for an older one, and several readers sent in contenders. The problem with many of these is that it gave definitions for “male gametes” or “female gametes”, but not for the sexes themselves, so I didn’t count them. (It’s clear, though, that the recognition of sexes based on gamete types goes way back.
But for formal definitions, we now have two more, and both are again from Alex. They push the first formal definition I know of back to 1895.
Here’s the first, with the definition bolded by Alex:
J. B. Haycraft, ‘The Role of Sex’, Natural Science: A Monthly Review of Scientific Progress (September 1895), p. 196
Here, we meet with two distinct kinds of dimorphism, both of which may be termed sexual. In the first place, the special reproductive cells, or gametes , are different from each other, and this we may term dimorphism of the gametes; and in the second place, the whole individual may be dimorphic, dimorphism of the individual.
Thus, in Hydra, one individual specimen produces two kinds of reproductive cells or gametes, and these may be termed male and female gametes . One individual hydra does not, however, differ from another individual hydra- there are no male and no female hydras the individual may be termed hermaphrodite , from its producing both male and female gametes. In by far the larger number of plants and animals a division of labour occurs, and the male gametes are produced by one individual, the females by another, so that in this case we may speak of a male and female individual, more especially as these individuals generally come to differ from each other in qualities other than that of merely producing different reproductive cells.
I would say that this counts, though it adds other characteristics that differ between males and females as well.
Here’s one from 1911 that comes pretty close, but gets no cigar because although it implies two sexes producing different types of gametes, it doesn’t define the sexes that way.
1911, “Some Problems of Evolution in the Simplest Forms of Life”, by E. A. Minchin:
The essential feature of the sexual process, throughout the whole series, is the production by each individual, male or female, of peculiar cells, termed gametes, which are set free from the body, or at least from the organs in which they arise. The gametes produced by each sex are very different in size, form and appearance.
The 1924 one mentioned yesterday is still the most unequivocal definition of the sexes, and if I were writing about this I’d say something like “A definition of the two sexes based on producing different types of gametes appears to have arisen around the beginning of the 20th century.”
Great.
It’s very helpful for people fighting against anti scientific ideas to have these examples.
Problem of course: arguments that surely will be heard from the activists:
This is from white, male scientist from the late 1800/early 1900, a time of eugenics and racism:
Their conclusion: The idea of the sex binary is white supremacy racist, sexist……-ist (fill in ) idea…….
+1
Thanks! Good example of crowdsourcing a solution to an awkward problem that needs specialist knowledge of the literature.
To be somewhat fair to those who would differ in how to best define the sexes, definitions that date to times much older than the discovery of gametes would surely have only used descriptions of anatomy and means of procreation. Gametes having not yet being discovered.
But anatomical descriptions of the sexes will differ wildly among the metazoans. Gametes are the only means to define this stuff in a universal sense. To me, that is the most important thing, then. Although other, more informal definitions in textbooks will still abound.
But how strange it is that we have well educated individuals trying to promote revisionist thinking about this matter only because some people identify as trans-gendered and they wish to help their feelings. That is the ONLY reason why this debate about physical reality is even happening. In a parallel universe exactly like this one but without transgendered people, this debate would not be happening at all.
Yes, in this universe my mind tells me that I identify as a man. I have no choice in that, and since this arises from my mind I can fairly say that this view of myself comes from my imagination. Someone else with full-on male anatomy (and male gametes) may have a mind that just as sincerely tells them that they are a woman. But that opinion– that imagination – does not make them a biological female. It does not change anything physical about them.
“and they wish to help their feelings” … indeed. Someone wants it to be true and so produces the argument that it is true. There is a nice new essay that expands on this question of argument from belief/wish rather than evidence by the ever-eloquent (and delicately humorous) Kathleen Stock at Unherd this week
https://unherd.com/2024/02/whos-scared-of-a-female-brain/
It’s interesting that these latest references refer either to the “Simplest Forms of Life” or to unusual forms, such as hydra. (Of course a hydra isn’t unusual to another hydra.) I wonder when the sex definition based on gamete size was first used in “higher” organisms, such as mammals and birds. Perhaps Horacio Hackett Newman (from yesterday’s post) was earliest. The search continues.
I have never quite understood why (other than politics) everyone seems to insist on either “gamete size is _the_ definition of sex, and anyone who says otherwise is blinded by ideology” or “gamete size is a stupid definition of sex that no one uses except because they’re blinded by ideology”, when it looks to me as if the actual situation is “the term ‘sex’ can mean a bunch of different things and different definitions are appropriate at different times, and sometimes gamete size is what you want and sometimes not”.
If for whatever reason you want a definition that you can apply to absolutely every species that can be said to have sexes at all, then gamete size seems like the obvious choice; so far as I know there are no anisogamous species for which this doesn’t yield a reasonably clean classification.
If for whatever reason you want a definition that applies to humans and e.g. gives results consistent with most people’s informal classification, then you probably need something a bit different because e.g. someone with Y chromosomes but CAIS would produce small mobile gametes if they produced gametes at all (my understanding is that they don’t produce functioning gametes, but what they do produce are “incomplete spermatozoa” rather than “incomplete ova”) but almost everyone would classify them as female if required to pick.
And … none of this seems like it needs to be controversial? Except that for whatever reason Team Anti-Trans and Team Pro-Trans have grabbed onto it as something to shout at one another about. I’m pretty sure that if you’d asked the exact same people 20 years ago, they’d all have agreed that (1) you can define sex in terms of gamete size if you like, and it gives reasonable results across every anisogamous species, and that (2) you can define it other ways too, if you have some narrower context in view than “every anisogamous species”, and that (3) different definitions are good for different things.
And it’s not even as if this actually has much to say about any of the actual disagreements between Team Anti-Trans and Team Pro-Trans. I mean, no one is going to argue “Usage of sex-segregated public bathrooms must go by natal sex, because sex is defined by gamete size and mobility”, or “Trans women must compete on an equal footing with cis women in sex-segregated sporting events, because the gamete-size definition of sex is stupid”: obviously nothing remotely like either of these makes any sense. Or at the individual level: “I will not call you ‘she’, because I have inspected your gametes and they are small and mobile.” “Your male-typical anatomy is no obstacle to welcoming you to our sexual abuse survivors’ support group, because biologists shouldn’t define sex in terms of gamete size.” Again, neither of these would make the least bit of sense.
You’ve missed the point, here. The relevance of the gamete-based definition is that it shows sex to be:
a) real (it’s not “constructed”: it’s an objectively observable phenomenon)
b) binary: there only two sexes, and basically every person is either one or the other; and
c) immutable: you can’t change from one to the other (at least mammals can’t do this).
This is highly relevant to the debates with trans-activists. The arguments of trans activists don’t survive a recognition of those basic facts about sex. Hence, their arguments invariably involve some form of sex denialism.
*Of course* the arguments for sex-segregated sports don’t amount to claiming that an individual’s small gametes provide him with a direct competitive advantage. The point is that there is massive performance gap between males and females (thus sex segregation is needed to achieve fairness and safety), and there’s no real difficulty in identifying which ones the males are. The case for sex-segregation doesn’t follow directly from the definition of sex: you can imagine a possible world in there’s no performance gap between males and females, in which case there would be no need to segregate sports (much as we don’t segregate poetry competitions).
p.s. I’m not convinced that a CAIS individual represents a counter-example to the gamete-based definition. I assume those DSDs occur in animals also, so there’s no reason why this poses a problem for defining sex in humans but not in other species. The obvious way of viewing the individual you describe is that they are technically male, though with some anatomy typically observed in females.
The gamete-based definition shows that _one useful notion of sex_ has those properties.
That’s perfectly consistent with e.g. the idea that if you want to decide what sex a particular _human being_ is, you should do it by some means other than examining their gametes. And it’s perfectly consistent with pretty much any such means you might choose.
If someone says “if we want to know what sex a person is, we should decide that on the basis of their self-image” or “… on the basis of their anatomy” or “… on the basis of testing their chromosomes” then that might be a great idea or a terrible one, but we can’t tell which just from the fact that there’s a very general definition of sex in terms of gamete size that’s useful when looking at broad generalizations across all anisogamous species.
(For something to be credibly called a notion of sex, it had better _usually agree_ with the gamete-based definition. But they all do, even e.g. “your sex is whatever you feel it is”: most people who feel that they are male have small mobile gametes, and most people who feel that they are female have large less-mobile gametes.)
Again, it might turn out that any particular candidate definition is a terrible one. Maybe it turns out that all the good ones have the three properties you list. But you can’t tell whether that’s so just from the fact that the gamete-size definition is useful sometimes and has those properties.
I’m not saying that people with CAIS are counterexamples to the gamete-size definition. What I’m saying they’re counterexamples to is _the idea that we should use the gamete-size definition for classifying human beings_, because for pretty much every purpose we’d ever want to classify human beings’ sex for those people are a much better fit for the “female” category than for the “male” category. Do they have men’s advantages in strength-based sports? Nope. Do they have men’s tendency to be more aggressive and violent? Nope. Do they tend to be androphilic or gynephilic? Androphilic. Is an abuse victim who gets uneasy at the presence of anyone male-looking likely to be troubled by them? Nope. Are they about as likely to be rape victims as the average woman, or the average man? Woman. How do they tend to think of themselves? As women. How do other people tend to think of them? As women. What genitalia do they have? Pretty much typical female. Etc.
(There are a few exceptions. E.g., people with CAIS almost always don’t have uteruses, so if you’re doing something like screening for uterine cancers then you want to treat those people differently from most other women. But we don’t generally say that people who have had hysterectomies aren’t female.)
If you have some sex-based policy concerning human beings and you need to pick a definition of sex to use for it, you should probably not pick the gamete-size definition: it gets some cases unambiguously wrong, without getting other cases righter than competing definitions to compensate. And, therefore, the fact that the gamete-size definition exists and is useful for some purposes tells us nothing about what sex-based policies we should be applying among human beings.
(It’s probably true, though I don’t know, that CAIS-like phenomena can happen in other species of animal besides humans. I don’t see how that’s an argument in favour of insisting on the gamete-size definition as the One True Definition Of Sex, which seems to be roughly your position: what it means is that there are other cases besides human ones where the gamete-size definition classifies particular organisms in a way that’s generally unhelpful.)
Thanks for the detailed response, G. Again, I think you’re missing the point.
I’m not aware of anyone who thinks we should “examine someone’s gametes” in order to determine what sex they are. Clearly, there are more practical ways of going about this. One of these is to make a judgement based on appearance (when it comes to adults, it’s pretty obvious what sex they are in the vast majority of cases). Another is a DNA test, testing for the presence of a Y chromosome. Anyway, the question of how we go about determining whether an individual is male or female, is completely separate from the question of how sex is defined (previous blog posts on this site have emphasised this distinction).
Likewise, I’m unaware of anyone engaged in these debates who is primarily concerned about excluding the CAIS individual you describe from rape centres or other female only spaces. Of course I agree that such a person should be *treated as a female* for those purposes. This is entirely consistent with saying that, following the definition of biological sex, the person is male. In fact, it makes perfect sense that someone who insists on a gamete-based definition will favour a policy that allows for such an individual to be included in female only spaces: as you say, the person has almost all of the characteristics typically expected of human females (i.e. expected of large-gamete producing adult humans): *female* appearance, *female* genitals, *female* propensity to violence etc etc.
It’s helpful to get clear on why it’s become necessary to re-assert the gamete-based definition. It’s because we’re contending with is a brand of activism opposed to *any* type of sex categorisation, other than one collapses sex into gender identity. We’re told that sex is either a spectrum, or something racist Europeans came up with a few centuries ago, or that it’s just so complicated and impossible to define and we should stop trying to do so. It’s in the face of absurd arguments such as this that there is a need to point out that actually we have a very straightforward definition of sex (based on gametes). In short, it’s the sex denialism that’s at issue here. If you doubt this, then see if you can get a transactivist to agree that transwomen are male.
I found a definition in a book by Ernst Haeckel (1834-1919) that was published in 1866:
“Das getrenntgeschlechtliche Individuum mit Ovum, ohne Sperma, wird allgemein als weibliches (femininum), das nichtzwittrige Individuum mit Sperma, ohne Ovum, als männliches (masculinum) bezeichnet.”
—
“The dioecious individual with ovum, without sperm, is generally designated as female (femininum), the non-hermaphroditic individual with sperm, without ovum, as male (masculinum).”
[my transl.]
(Haeckel, Ernst. Generelle Morphologie der Organismen. Zweiter Band: Allgemeine Entwickelungsgeschichte der Organismen. Berlin: G. Reimer, 1866. p. 61)
[The book is freely available & downloadable at GoogleBooks.]
Very cool!
So many basic things trace to Haeckel! Phylogeny, phylum, ecology, and perhaps this.
I looked up “anisogamy” in the OED, and got this: https://www.oed.com/dictionary/anisogamy_n?tab=meaning_and_use#993163064
1891
*Anisogamy: the union of two gametes differing chiefly in size.
Hartog in Nature 17 September 484/1
…that Nature article is:
Biology at the British Association. Nature 44, 481–484 (1891). https://doi.-org/10.1038/044481a0
Pages 483-484 discuss a presentation by Hartog…
[p. 483] “Prof. Marcus Hartog communicated an outline classification of sexual and allied modes of protoplasmic rejuvenescence.”
[p. 484 contains a large classification of reproductive modes, including:]
“B. KARYOGAMY: the union of cells (gametes), cytoplast to
cytoplast and nucleus to nucleus, to form a 1-nucleate
cell, the zygote. The following variations occur: —
1. ISOGAMY. The union of gametes indistinguishable in size, form, and behaviour; this may vary as follows :-
[…]
2. ANISOGAMY : the union of two gametes differing chiefly in size ; the smaller (micro-) gamete is male, the larger (mega-) gamete, female.”
[…]
And later:
IV. PARAGENESIS will include the following modes, usually grouped under the term parthenogenesis, apogamy (pro parte), &c.:-
A. TRUE PARTHENOGENESIS: the direct development of a facultative gamete without karyogamy. This may occur in the case of-
(1) Isogametes; (2) Anisogametes (male and female); (3) Oogametes.”
The practical reason for accepting a person with CAIS as female is that by the time the diagnosis is made, the person has been living as a normal-appearing girl -> adolescent woman for 14 years or more. (Some athletes remain undiagnosed into their 20s because their failure to start menstruating is put down to high-intensity training during adolescence.) If someone was observed and registered as a girl at birth, looks outwardly like a girl since birth, and lives comfortably like a girl, you can’t tell this teenaged girl no unhappier than anyone is at that age that she is “really” a boy/man.
The girl will often develop typical female secondary sex characteristics at puberty because the testosterone produced by the abdominal testis will be converted to estradiol in fat tissue, feminizing her body as you would expect. Regardless of how you communicate the diagnosis, you can’t call her anything but a woman. She will leave “F” on her government documents and no one else in the whole world need know that she has a Y chromosome and testes (which latter may need to be removed to prevent cancer.) People who are trying to point to women with CAIS as violating the binary will have to figure out whom to point at. They are completely invisible in ordinary life.
Here’s something from 1890:
“The essential attribute of the male sex is the generation of spermatozoa, that of the female the generation of ova, accomplished in the one case by a testis or a homologous organ, and in the other by an ovary or a homologous organ.”
(“Sex” in The Century Dictionary: An Encyclopedic Lexicon of the English Language; Vol. 5. Edited by William Dwight Whitney. New York: The Century Co., 1890. p. 5535)
“Spermatozoa are the vital and essential product of a spermary, male gonad, or testis, as ova are of the ovary or female gonad; their production, or the ability to produce them, is the characteristic distinction of the male from the female organism, whatever their size or shape or other physical character, and however various may be the organ in which they are produced.”
(“Spermatozoon” in The Century Dictionary: An Encyclopedic Lexicon of the English Language; Vol. 5. Edited by William Dwight Whitney. New York: The Century Co., 1890. p. 5819)
[The book is freely available and downloadable at GoogleBooks.]
Darwin figuring out, and proving, the sex of pedunculated cirripedes (stalked barnacles) with parasitic males in 1851:
http://darwin-online.org.uk/content/frameset?itemID=F339.1&viewtype=text&pageseq=1
“Concluding Remarks.—That these animals are true Cirripedes, though having so different an external appearance from others of the class, admits of not the least doubt. The prehensile antennæ, enveloped in cement and including the two cement-ducts, would have been amply sufficient, without other parts—for instance, the mouth, by itself perfectly characteristic with each organ, together with the whole alimentary canal, constructed on the normal plan,—to have proved that they were Cirripedia. Under the head of the closely-allied Ibla quadrivalvis, we shall, moreover, see that the males are developed from larvæ, having every point of structure—the peculiar quasi-bivalve shell, the two compound eyes, the six natatory legs, &c.,—characteristic of the Order. But in some respects, the males are in an embryonic condition, though unquestionably mature, as shown by the spermatozoa;—thus, in the thorax and mouth opening throughout their whole width into the cavity of the peduncle, that is, homologically into the anterior part of the head, and in the viscera being there lodged instead of in the thorax and prosoma, there is a manifest resemblance to the larva in its last stage of development: the absence of a probosciformed penis, the spine-less peduncle, the food being obtained without the aid of cirri, and the length of the rectum, are likewise embryonic characters. Not only are these males, as just remarked, Cirripedia; but they manifestly belong to the Pedunculated Family. If a specimen had been brought to me to class, without relation to its sexual characters, I should have placed it, without any hesitation, next to the genus Ibla; if the mouth alone had been brought, I should assuredly have placed it actually in the genus Ibla: for let it be observed how nearly all the parts resemble those of Ibla Cumingii, excepting only in size and in being less hairy. The trophi are arranged in the same peculiar position as in the female; the labrum is largely bullate, without teeth on the crest; the palpi, though relatively smaller; are of the same shape; so are the mandibles; the maxillæ are more rounded and less prominent, but have the same
[page] 199
exact size relatively to the mandibles; the outer maxillæ have the same, quite peculiar pointed outline, and the olfactory orifices are tubular, and hold the same unusual position. It is most rare to find so close a resemblance in the parts of the mouth, except in very closely allied genera, and often species of the same natural genus differ more. Again, in the long œsophagus and constricted stomach there is a resemblance to Ibla. In the male of Ibla quadrivalvis, the caudal appendages are multiarticulate; now, this is a character confined to four genera, namely, Ibla, Alepas, Pollicipes, and Lithotrya. I may add, that large tubular olfactory orifices are confined to the same genera, together with Scalpellum. Lastly, it particularly deserves notice, that the prehensile antennæ, in having a hoof-like and pointed disc, with a single spine on the heel, much more closely resemble these organs in Scalpellum, certainly the nearest ally of Ibla, than in any other genus; they differ from the antennæ in Scalpellum, only in the ultimate segment not having a notch on one side. These organs, unfortunately for the sake of comparison, were not found in the female and ordinary form of Ibla. The full importance of the above generic resemblance in the antennæ, will hereafter be more clearly seen, when their classificatory value is shown in the final discussion on the sexual relations of Ibla and Scalpellum.
Here, then, we have a pedunculated Cirripede very much nearer in all its essential characters to Ibla than to any other genus, and exclusively of the male sex; and this Cirripede in six specimens, from two distant localities, adhered to an Ibla exclusively of the female sex. May we not, then, safely conclude that these parasites are the males of the Ibla Cumingii? Considering that, in the same class with the Cirripedia, there is a whole family of crustaceans, the Lerneidæ, in which the males, compared with the females to which they cling, differ as much in appearance as in Ibla, and are even relatively smaller, I should not have added another remark, had there not been under the head of the following species, and of the next genus
[page] 200
Scalpellum, a class of allied facts to be advanced, which in some respects support the view here taken, but in others are so remarkable and so hard to be believed, that I will call attention to the alternative, if the above view be rejected. The ordinary Ibla Cumingii must have a male, for that it is not an hermaphrodite can hardly be questioned, seeing how easy it always is to detect the male organs of generation; and we must consequently believe in the visits of a locomotive male, though the existence of a locomotive Cirripede is improbable in the highest degree. Again, as the little animal, considered by me to be the male of I. Cumingii, is exclusively a male, (for there were no traces of ova or ovaria, though the spermatozoa were perfect,) we must believe in a locomotive Cirripede of the opposite sex, though the existence in any class of a female visiting a fixed male is unknown:* in short, we should have hypothetically to make two locomotive Cirripedes, which, in all probability, would differ as much from their fixed opposite sexes, as does the Cirripede, considered by me to be the male of I. Cumingii, from the ordinary form. This being the case, I conclude that the evidence is amply sufficient to prove that the little parasitic Cirripede here described, is the male of Ibla Cumingii.”
Commentary on Darwin’s barnacles work, at the Darwin Online site:
http://darwin-online.org.uk/EditorialIntroductions/Richmond_cirripedia.html
“Perhaps the clearest example of how Darwin’s transformist views may have influenced his taxonomic decisions comes from his discussion of the sexual relations of cirripedes. The hermaphroditism of cirripedes is one of the major characters distinguishing the majority of the group from other crustaceans. Soon after commencing the monograph, however, Darwin discovered in the genus Ibla a species in which small, rudimentary males were found parasitic on the female. Subsequently Darwin encountered a further sexual peculiarity which he regarded as even more significant. In both Ibla and Scalpellum, he also found minute or, as he called them, ‘complemental’ males attached, not to a female, but to a hermaphrodite. Apart from the ‘marvelous’ fact that these complemental males were so ‘utterly different in appearance and structure’ from the hermaphrodite—the two representing such ‘diverse beings, with scarcely anything in common, and yet all belonging to the same species!’ (Living Cirripedia (1851): 293)—this discovery was unique in the animal kingdom, and it touched upon, Darwin realised, the question of sexuality and its evolution. [8]
[…]
8 This phenomenon had long been recognised by botanists; Darwin, in fact, referred to the analogy with plants in Living Cirripedia (1851): 214: “Although the existence of Hermaphrodites and Males within the limits of the same species, is a new fact amongst animals, it is far from rare in the Vegetable Kingdom: the male flowers, moreover, are sometimes in a rudimentary condition compared to the hermaphrodite flowers, exactly in the same manner as are the male Iblas.” Darwin’s earlier interest in the question of hermaphroditism can be seen in his Notebook D (Notebooks, 1987), where he developed the theory of the origin of separate sexes from an ancestral hermaphroditic organism.”
Here are two definitions, one from 1891 by Thomas Jeffery Parker (1850-1897), and the other from 1892 by Marcus Hartog (1851-1924):
“Notice that in this case the conjugating bodies or gametes are not of equal size and similar characters, but one, which is conveniently distinguished as the microgamete (= microzooid) is relatively small and active, while the other or megagamete (= megazooid, or ordinary individual) is relatively large and passive. As we shall see in a later lesson, this differentiation of the gametes is precisely what we get in almost organisms with two sexes: the microgamete being the male, the megagamete the female conjugating body.”
(Parker, T. Jeffery. Lessons in Elementary Biology. London: Macmillan & Co., 1891. p. 130)
“The process we have just studied is termed “conjugation,” the cells that unite are termed “gametes,” and the resulting cell called a “zygote”; and we have here the key to all processes of conjugation and of fertilisation, since this is the most primitive type. In certain forms allied to Ulothrix, more than two gametes—as many as six—may unite to form a single zygote. In other cases, again, we find the gametes all similar in form, but evincing in size and behaviour a division into two types: the one smaller and more active, the other larger and more sluggish. This differentiation affects the cytoplasm far more than the nucleus. It may advance so far, that the larger cell is enormous and motionless, or nearly so, while the smaller cell is reduced to a nucleus, with just enough cytoplasm to enclose it and carry it to its destination. This differentiation of size and activity is what we term sex. The larger gamete is the female, ovum, or egg; the smaller is the male, or spermatozoon, whose flagellate type is retained in the highest animals, betraying still their lowly origin.”
(Hartog, Marcus. “Problems of Reproduction.” In The Contemporary Review, Vol. LXII, 92-104. London: Isbister & Co., 1892. p. 94)
[Both books are available at GoogleBooks.]