Reproduction is pretty exciting to a biologist: you had a critter and now you have more of them, which is fun if you study molecules and cells and fun if you study populations and ecosystems, and anything in between. Sadly, by contrast, “sex” is a rather boring word when a biologist gets hold of it, because it means combining genetic material across individuals and that is all. It’s interesting to be sure but when viewed in its original and most explicit form, much less fun than what you were expecting. Like so (warning! all the naughty conjugation is just simulation! rip!).
Remember from Breath of life, A, A and B, A+B, and B (having lost A). That’s what reproduction and sex have done in multiple lineages of living things.
- Bacteria & similar (prokaryotic, single cells): A and B
- Reproduction via cell division, making clones / Sex via genetic transfer, without reproduction
- Protists (eukaryotic, single cells and/or colonial): A and B, A+B
- Reproduction via cell division, making clones / Sex via a wide range of genetic tricks, sometimes associated with reproduction and sometimes not
- Plants, animals, fungi (eukaryotic, multi-celled organisms): A+B, B
- Sexual reproduction using gametes, representing a two-step between chromosome numbers in cells (one set / two sets)
- Note: cloning via larger-scale tissue separation is retained in in many species, so there’s some [A and B] still around; also, fungi do other wild things at which plants and animals only stare
- Note: these three groups represent two or three separate origins of certain phenomena, of which gametic sex is probably one
As the Reb says in a different context, “all else is commentary.” For a big multicellular creature such as ourselves who use gametes, they apparently occur in two types per species, not one, not three, not eighty-eight – always two. Roughly distinguishable as “big ol’ stationary” and “li’l mobile,” although the means of the latter’s transport varies greatly – plant pollen are windborne or or piggyback on animals; animal sperm wiggle on their own. This twoness, or digametic sex, is the only way to do it, or so the theoretical math people tell us.
The respective names of this sex, not that one, out of two, strictly speaking applies only to gametes and has no inbuilt meaning or implication beyond its defining fact. I am “male” only insofar as that’s the kind of gamete I can make, for instance, but that’s getting ahead of ourselves, and let’s take a broader view. Apparently the original way to do this, and a sensible one it seems, is for one’s species to feature the production of both gamete types per individual, which is what hermaphrodite means, and if so, either simultaneous or sequential.
This has been modified in many lineages to a single gamete type per individual, such as ourselves as a member of the amniote vertebrates, which is where the aforementioned male-me point applies, or just as a grab-it example, marijuana plants as a member of the urticalean rosids. Mixing things up a little, some species include individuals for which sexual reproduction is obviated in some way, becoming neuter.
Our history represents more loss than gain. A bunch of us animals have lost the capacity to reproduce asexually, so we’re left with “plan B” alone, as obligate sexual reproducers. Then a somewhat smaller set of animals in our ancestry have lost as well the two-gamete-type capacity, such that each of us can only make one type. [this history of loss with varying details has occurred many times, of which our lineage is merely one] Only in this limited context do we now speak of “you” and “me” as male or female, and – stay with me here – whatever variety of anatomies and behaviors are associated with either are later, local evolutionary events.
Not quite like Hedwig’s song, because we’re not talking about two individuals as identifiably different but conjoined sexes, and also acknowledging the points regarding sexual preference in partners as strictly symbolic, but still, with a classical pedigree from Socrates and a great song anyway:
About now you’re drumming your fingers: get on with it. OK. We’re talking now about anatomical and behavioral doohickeys by which in the fullness of time the chance goes up that two differently-sexed gametes will be in one another’s personal space. (Didn’t I put that nicely?) It breaks down to internal vs. external fertilization, and internal vs. external gestation, for which all four combinations are observed, as well as certain grey/boundary cases.
As an obligate sexual reproducer, with one sex per individual, with internal fertilization and internal gestation, our little profile of parts and practices – even as a representative of the majority of Mammalia – is a mighty narrow suburb of the vast sexually reproductive metropolis.
Hey wait, isn’t this all just that XX and XY thing? It’s all “genetic,” right? No. Throw that crap outta there, it’s a perfect example of a minor suburban development projected onto the entire landscape. See that animal diversity? Get this: most animals set up all this weird anatomy and behavior without designated sex chromosomes. Yup – uteruses and penises and the plethora of similar stunts like hemipenises and ligula and brood flaps and what-all, evolving all over the place with nothing but the ordinary typical autosomes. Most especially, in the ancestry of animals such as ourselves, for whom the components of our complex anatomy and physiology of sexual reproduction were all long-established … wait for it … before this lineage had X and Y chromosomes.
Don’t be distracted by the chromosomal effect beginning the physiological sequence of events – it evolved into that initiatory signaling position after that sequence had already been established. It’s a huge, key evolutionary point: just because a certain sequence of events goes 1-2-3-4 today, doesn’t mean those steps evolved in that order. Typically, 2-3-4 evolves in very simple form first, becomes more complex, and gets 1 added to it much later. So don’t blither at me about how “male is XY,” or whatever – XX vs. XY is merely the way modern mammals signal their older developmental sequences to begin now.
Yup. That’s why you see distinctive and different chromosomal signaling mechanisms out there, scattered around … let’s see, birds with their hw system, a bunch of insects with XY and XO tricks, and mammals with their XY … each one embedded in a much larger phylogenetic group with the same or similar anatomy and physiology without the sex chromosomes.
You’re with me so far, right? Male and female as completely separate, indeed at a completely different level, from implications or identity as masculine and feminine? That even what’s grudgingly acknowledged as sex in modern parlance, what I call dimorphic anatomy , is still in the realm of “options” as far as life-on-earth is concerned? That what we call sexual and gender diversity are mere party hats within our suburb regarding copulatory escapades, fully-experienced and culturally highlighted as they may be from inside it?
All of which lead me and any biologist I’ve ever met to be blase about such things to the point of social unacceptability. The term unnatural simply doesn’t occur to us in reference to sexual acts or hold weight when spoken in our presence.
… which brings me to the title topic, the word “hermaphrodite,” which in biological terms applies to no actual human person living or dead. At least in the sense that biologists become insufferable in the produce section when we see cucumbers and tomatoes called vegetables. But also relevant in terms of the insupportable weight assigned to specific conditions far beyond their actual features. This blunt statement comes from the observation that all the amniotic vertebrates (turtles, snakes & lizards, crocodilians, mammals, birds) are single-sex, producing one gamete type per individual, often with differing anatomy and physiology associated with the particular type. Conditions called hermaphroditic in such animals, including humans, are actually something different.
In animals, there are three subdivisions of reproductive anatomy (as opposed to secondary sexual features): gonads, ducts, and genitals. Embryos begin with indeterminate structures which then become working organs through development. The breakdown in most mammals goes like this:
- homology in the gonads, meaning, ovaries and testes are the same organ
- don’t be distracted by the testes’ shift in position in most mammals; they develop in the same spot
- non-homology in the ducts, meaning, seminiferous tubules and the oviduct are different organs, with completely different tissue origins and developmental mechanisms
- homology in the genitals, meaning, the vaginal canal, labia, and clitoris and (in that order) the closed inguinal canal, scrotum, and penis are the same organs
[fun detail: a number of mammals retain the cloacal anatomy, or variants on it, observed in turtles and some birds – doesn’t change any of my points here, but worth a post later]
Let’s get into this now. It relies on a deeper understanding of evolutionary change. Most students coming into my classes knew about genes and traits. What they didn’t know, or didn’t know that they already knew if they thought about it, was that genes don’t “do” or “make” traits – they influence the development of traits. Their familiar terminology of a gene “for” this or “for” that masked the actual processes of what genes do, and that the features we see and experience are outcomes of developmental events. But if what a gene does is a trait, then that term very properly applies to developmental processes as much as it does to the observed and experienced feature, or more so. Hence developmental traits as an evolutionary category unto themselves, or as we like to call it, Evo Devo.
Which finally, finally positions us for discussing the phenomenon of intersex outcomes, best understood as variants on all of the above. The easiest to understand is the range of genital outcomes with little reference to the other parts: merely look across that third row and come up with any intermediate state between the homologues. The range is therefore very wide in terms of detail, but the phenomenon is a single thing. The effects of developmental hormones (or the more general and recent word, morphogens) have complex physical effects in a multivariate physical environment, and their effects turn out a bit differently every single time, without even a special genetic explanation or anything else all by itself. Most of the outcomes fall into the identifiable ends; some don’t.
I advise against learning from porn for just about anything, but in reference to intersex conditions, the famous imagery of a penis + breasts – obviously interesting to Greek sculptors as well as to anyone else – is not biologically iconic. It’s one result of these less-common outcomes, for a clitoris to develop exactly as it might in someone else.
There is one other condition or range thereof to discuss, called androgen insensitivity.
A quick point about breasts: the default or “indeterminate” form in humans is to have small breasts. They are typically increased in size and provided with mammary glands due to estrogenic effects in puberty, and in males, suppressed due to androgenic effects. A person with androgen insensitivity displays neither of these effects (no estrogen and no response to testosterone) and therefore has small breasts.
So, male? Female? Intersex? Again: the biology only sets up the situation, it doesn’t say a thing about various “is”-s that we insist must exist, and here as is so often the case, tells us that the “is” isn’t. My aim here is to demystify and de-mojo the whole thing, to show you why biologists are the ones who don’t point at people with intersex genital form as unnatural freaks or take it as a given that they be surgically altered at birth, or flinch and peer and whisper about which celebrity is a “hermaphrodite” (i.e. androgen-insensitive). I was romantically involved with a woman with this condition for a couple of years, and can report that there was nothing to report.
Please don’t pretend biology justifies exoticizing or diminishing people, all of whom are fully people featuring understandable variants of the ordinary variables. When examined, it never actually does.
Next: Get away from her, you Naturalistic Fallacy!