Sex: the binary-spectrum debate
Yes, there are only two gametes, but is that enough to take into account the whole of biological sex in humans and other animals?
Scientific theory and political expediency have a long and tense relationship. Copernicus and Galileo were inconvenient for the Church, Nazis despised “Jewish” physics but loved genetic determinism (which they inherited from, mostly, American “scientific” racists), Stalin persecuted evolutionary biologists. Today, many in the left (and, in growing numbers, in the alt-right) have trouble accepting that GMOs and pesticides — the latter, if properly and correctly used — are safe and necessary for the survival of our species in its present numbers.
Given this complex history, it’s no surprise that scientists become wary of any perceived sign of ideological encroachment in their fields of expertise. Attempts to twist the arm of science to make it “confess” to politically convenient (“correct”) narratives are resisted, as they very well should be — but this necessary vigilance may sometimes get on overdrive and generate false positives. Some biologists have sounded the alarm after noticing a growing number of publications, and even fellow researchers, redefining biological sex from “binary” to “spectrum”. Are their concerns warranted?
The classic, binary vision is quite straightforward and makes perfect sense. It goes like this: in animals (including Homo sapiens) there are only two kinds of reproductive cells, or gametes. One that is large, heavy and almost motionless — in humans, the egg — and another that is small, light and fast moving — in humans, the sperm. You then define as “females” all the individuals who produce (or are primed to produce) the large, heavy cells and as “males” the ones that make (or are primed to make) the small, light ones. And that is that.
This definition works well for lots of purposes, including the distribution of IgNobel Prizes! In 2017, the Biology award went to a group of scientists that had discovered a species of fish in which the male (i.e., sperm producer) has the vagina and the female (i.e., the egg producer), the penis.
Darwin’s passionate male
For a long time, it was widely believed that this difference in gamete size, technically calls “anisogamy”, had great explanatory power, too, allowing us to understand why females (using Charles Darwin’s words from 1871) tend to be “coy” and choosy and males, “passionate” and promiscuous.
Nowadays, however, both the premise — that female coyness and male promiscuity are common, stable characteristics throughout the animal kingdom — and the conclusion, that anisogamy represents a good explanation for this purported universal trait, are sagging under the weight of the accumulated evidence, both anthropological and ethological, from the last 150 years, and also of human history: if promiscuity is predominantly a male characteristic and females are really not that into it, why do we have 5,000 years of god-given commandments, common prejudices and man-made laws to scare women away from sex in general and from adultery, in particular?
Anyway, you can find a lot about the actual state of the art on these subjects here, here and here.
So, the binary is real (there really are only two kinds of gametes in animals) and sort of useful, even if its explanatory power is not all that it was cracked up to be. So, what’s the problem? Where does this “spectrum” gimmick come from? Why would we need it?
Well, for one thing, gametes are not the only way sex shows up, biologically. Even if you try to separate behavior and feeling from biology (something that, seriously, only works if you believe people have ghosts living in their skulls, piloting their bodies; otherwise, everything is biological, one way or another) and, doing some conceptual acrobatics, decide to banish every individual trait that is “not of the body” to the Siberia of “gender”, you still get stuck with situations like Swyer Syndrome.
Girls and women with this syndrome are, as far as their observable exterior characteristics go, girls and women — they have vaginas, they have uteruses. But their chromosomic makeup is XY (which would make them “males” in the minds of the genetic determinists) and they have no ovaries, nor testes: they make no gametes whatsoever. They just don’t fit in the binary. And they are a minority, yes, but not so small as many would think: a study conducted in Denmark puts the prevalence of XY females at 6.4 per 100,000 girls/women. In the US, it would correspond to almost 11,000 people. And that’s only one of the several congenital intersex configurations known to science.
Here we have a situation that makes thinking of biological sex as a spectrum useful. And it’s not the only one: there is a recent paper on toxicology that calls attention to the importance of recognizing intersex characteristics in medical research, going beyond the typical division of study participants in sex groups labeled “male” and “female”. It’s an eminently sensible proposition. Intersex or transex individuals may have — due to special genetic, hormonal, anatomical traits — reactions to medications and other substances that differ from the “usual” male/female ones.
Facts vs. concepts
There is no real, factual disagreement between proponents of the “sex as a binary” and of the “sex as a spectrum” points of view. No “binarian” denies that transexuals and intersex people exist (I hope!), and no “spectrarian” denies that there are only two gametes. The point is one of categorization or, to borrow an expression from the philosophers of science, of how to best “carve nature at the joints”.
What is more useful and fruitful, both scientifically (as a source of hypothesis, research programs, investigative strategies, testable predictions) and medically (as a way to better understand and promote human health): to carve biological sex in two neat, self-contained boxes (both of which, however, leave hundreds of thousands, or even millions, of people around the world out in the cold), or to place it in a spectrum with two very large bumps at the extremes, one being XX/egg-producing/female and the other XY/sperm-producing/male, and all possible combinations in between?
Is it more fruitful, for science — including the study of human and animal behavior, and of human and animal societies — and for medicine: to keep forcing biological sex into a gamete-dependent binary, or to expand the definition to include other characteristics and their combinations, and then treat it like a spectrum?
That’s the question that really should matter, and it seems, at least to me, that “spectrum” wins hands down; among other reasons, because it integrates real cases that the binary would just shrug off as “exceptions”. As a general rule, theoretical models that “solve problems” by rhetorically redefining their empirical inadequacies into irrelevance are not very good, or even very scientific, ones.
Sometimes, critics of the spectrum view build straw men arguments like “what are the other sexes, then?” This, really, is just disingenuous. A spectrum is not a sequence of intrinsically discrete states (“number of sexes”), but a kind of continuous flow, in which one element just fades into another: you can break it into arbitrary chunks and give each chunk a name (like we do with the electromagnetic spectrum: radio, visible, ultraviolet etc.), but you don’t have to! The extremes are easily distinguishable — radio waves pass through you without being noticed, gamma rays kill you — but things in the middle tends to be more messy.
Richard Dawkins — who today seems to be a staunch sex-binarian — wrote, years ago, a brilliant essay on the mistake that is to treat biological categories (in that essay specifically, he was referring to animal species) as discontinuous absolutes. It’s called “Gaps in the Mind”, and can be found in his book “A Devil’s Chaplain”. To quote a nice excerpt from:
“This way of thinking characterizes what I want o call the discontinuous mind. We’d all agree that a six-foot woman is tall, and a five-foot woman is not. Words like ‘tall’ and ‘short’ tempt us to force the world into qualitative classes, but it doesn’t mean that the world is discontinuously distributed”.
In that same essay, Dawkins creates a beautiful image of a contemporary human being holding the hand of their mother, and then the mother holds the hand of her mother, and on and on, until the line gets to our last common ancestor with the chimpanzees; then the chain makes a 180o bend and the ancestors of the modern chimpanzees come to hold hands with each other, until human an chimpanzee face one another.
We could even call it a spectrum of primates. We could also use some practical criteria (like the capacity to interbreed) to subdivide the line into chunks that we would then call “species”, but we don’t have to — and the extremes (the human and the chimpanzee) are, of course, easily distinguishable from one another; those in the middle, not so much.
If even different species can be conceptualized as fading continuously one into another in an evolutionary spectrum, why not see the biological sexual traits of individuals belonging to the same species as part of a developmental spectrum?
Political fears
So, is the proposal of redefining “biological sex” as a spectrum, integrating more characteristics than just the gametes one makes (or could make, or ought to make, or used to make — does a castrated animal stop being “male”?) a politically-correct ploy to bend the knee of Biology into submission before the heinous idols of LGBTQ+ Wokeism?
It doesn’t look like that’s the case: it seems more like an aggiornamento of medically and scientifically useful categories, to reflect a more complete and complex understanding of life processes and individual characteristics.
What we have, then, is a false alarm. But how loud it sounds!