Any YouTube video with the title “Orangutan skeltons bust the sex binary” is guaranteed to draw me in, and the very title makes me wary. How can skeletons bust the sex binary of any mammal, given that the definition of sex in mammals involves features (reproductive systems evolved to produce two very different kinds of gametes) that can’t be seen in a skeleton? Sure, you can often identify skeletons (especially of sexually dimorphic species like humans) by various bone traits, like hip-and-leg configuration, but such dimorphism is not 100% diagnostic, nor, more important, the definition of the sex binary.
What Alexandra Kralick has done in the video below, released three days ago, is show that in orangutans, which have two morphs of males in the wild, give a more or less continuous distribution of bone-size measurements, since one morph of males is intermediate in size between males and females. But a continuous distribution of bone sizes does NOT “bust the sex binary.” What it does do is “break the bone binary”, but that says absolutely nothing about whether sex itself is binary. It’s like showing that the distribution of human heights is not binary and therefore human sexes are not binary!
The video is not only misguided, but is also an embarrassment to the Leakey Foundation, named after Louis Leakey, which sponsors research on human origins and evolution. The Foundation is, in fact, putting its imprimatur on work that purports to show that, in primates (and presumably in humans, since Kralick generalizes her results beyond orangs), sex is not binary. I doubt the Foundation would really agree with that, unless they’re terminally woke (and anti-science).
At any rate, here’s the YouTube introduction to the 48-minute video, which includes Q&A at the end.
Meet Leakey Foundation scientist Alexandra Kralick and learn how orangutan skeletons bust the sex binary in this rebroadcast episode.
Kralick declares that the theme of her work is “casting light on problematic assumptions that permeate scientific narratives of biological sex,” and adds that she’s bringing “a feminist and queer approach to this work to show how biological sex is more complicated than either ‘male’ or ‘female’ but in fact sits on a spectrum.”
One might sense that there’s an ideological motivation behind this work and its conclusion, a motivation that leads to misleading conclusions. One would be right.
Click to listen:
I’ve taken a few screenshots of the slides. The one below argues that “biological sex is not dichotomous” (i.e. “binary”), but she leaves out the one trait that defines sex and shows that it is binary: the reproductive system and the gametes that it makes. To repeat myself, males have a reproductive system evolved to produce small, mobile gametes (sperm), while females have a system evolved to produce large, immobile gametes (eggs). There is no third type of reproductive system, and no other type of gamete. This is the definition of biological sex, not the traits listed on the slide. (Note that the slide depicts humans, not orangutans, showing that Kralick is making a general statement, not one limited to orangs (which of course also fit the sex binary).
In the wild (though Kralick says “not in zoos”), the male orangs have two morphs, “flanged”, with big cheek pads, big vocal sacs, and large body size; and “unflanged”, males who are smaller, though not as small as females, and also lack vocal sacs and don’t have big cheek pads. Flanged males are behaviorally and sexually dominant over unflanged males. The two classes of males, of course, are still both male, for both can produce sperm and mate with egg-producing females (the unflanged males in nature may be “female mimics” that deceive females to get mates, but we don’t know). There are three species of orangs (genus Pongo) that live in different places, and all three have the male size/feature dimorphism. This is what Wikipedia says about them:
Males become sexually mature at around age 15. They may exhibit arrested development by not developing the distinctive cheek pads, pronounced throat pouches, long fur, or long calls until a resident dominant male is absent. The transformation from unflanged to flanged can occur quickly. Flanged males attract females in oestrous with their characteristic long calls, which may also suppress development in younger males.
Unflanged males wander widely in search of oestrous females and upon finding one, will force copulation on her, the occurrence of which is unusually high among mammals. Females prefer to mate with the fitter flanged males, forming pairs with them and benefiting from their protection. Non-ovulating females do not usually resist copulation with unflanged males, as the chance of conception is low.Homosexual behaviour has been recorded in the context of both affiliative and aggressive interactions.
This suggests that the unflanged males are indeed either female mimics or males that are non-dominant or of lower fertility, and have to use force to get offspring. Regardless, they’re still called “males”: they are clearly not a third sex!
Here’s a picture of the two morphs of males taken from Wikipedia. First flanged, then unflanged; the differences in vocal sacs and cheek pads are clear. The unflanged male was at the San Diego Zoo, though Kralick says that unflanged males can’t be found in zoos (27:11).
Below is a plot of the “long bone length” of adult (A) and juvenile (J) orangs: flanged male (FL), unflanged male (UFL), and female (F). Note that in each of the five long bones, the unflanged males are intermediate in length between big males and smaller females. Importantly, note that the orangs are classified as either MALE or FEMALE, which Kralick apparently got from the museum specimens that she studied. (The sample sizes were quite small: there were, for example, only three specimens of unflanged males.)
Here are data for the ulna (arm bone), again clearly showing the intermediacy of the unflanged MALES between flanged MALES and normal FEMALES. But if sex is not a binary, how did they identify the specimens? No doubt the collectors used the presence of a penis or vagina (almost 100% correlated with biological sex in humans) as the identifer of males vs. females, though presence or size of penis is not the definition of “a male”.
You get the same kind of distribution from cross-sectional area of the long bones. Kralick says “These are the results that support the notion that biological sex is a spectrum.” (32:44).
Now where does all this come from? Whence the conflation of sexual dimorphism with the definition and dichotomy of sex itself? You might have already guessed based on the lecture and the fact that at the beginning it’s announced that the Leakey Foundation is collaborating on this with “the American Association for Biological Anthropologists LGBTQIAA group.”
Below is a slide from the talk asserting that these data “subvert the idea of the sex binary as natural and biological, thus altering the discourse that places value on biological causes for gendered social order.” Well, I get the part about subverting the sex binary, but to say that the sex binary is not “natural and biological” is simply wrong. You know this from the immense irony that although Kralick finds a “spectrum” using bone dimensions, she sees this only by dividing the data by sex: males (two types) and females. Here she recognizes that there are two classes, and not an intersex. As for its connection with gender, it’s opaque.
Note, though that in the talk Kralick does quote the outdated figure that “17 our of 1000 babies born are intersex” (1.7%), “the same proportion of individuals with red hair”. The intersex figure came from a flawed claim by Anne Fausto-Sterling in 2000, who used a very wonky way to decide who was “intersex.” (Fausto-Sterling later retracted this claim, but you still see it everywhere).
In fact, developmental variants are very rare, constituting only about one in 5,600 people (0.018 percent), and also don’t represent “other sexes.” This is the same proportion of the time that a tossed nickel will land on its edge rather than on “heads” or “tails”, yet nobody thinks that the results of coin-tossing are “non-binary.” Further, just like coins that land on edge are neither heads nor tails, so an intersex individual, rare as they are, are not “other sexes”, but the results of development gone awry. After all, natural selection has created two endpoints for animal sexes, male and female, though the developmental paths to those endpoints can involve chromosomes, temperature (in turtles), the social environment (yes, clownfish) , or genes. Indeed, the paths are many but there are only two endpoints (males and females); and a deviation from those two goals represents a very rare straying from the path.
Towards the end, Kralick says explicitly that one of her aims is to deconstruct the narrative that unflanged males are “deviant,” which I guess a couple of anthropologists have said (but I bet few would say that today!). The language of “deconstructing”, “subverting”, “undermining”, and “busting” supposedly conventional science is straight out of postmodern discourse.
This slide, which conflates sex and gender again, supposedly gives us lessons about humans, the only species, Kralick asserts, that do have gender.
The goal in this research is apparently to read into nature the spectrum of gender we see in human society, another example of what I call the “reverse naturalistic fallacy”—the idea that “what we consider good in humans must be observed in nature.” It’s a logically unsound way to valorize human identities. The double irony, though, is that Kralick not only affirms the sex binary, or at least accepts it, but also studies something in orangs that has nothing to do with gender. Unflanged males are variants, apparently frequent, and may represent an evolved reproductive strategy. Their existence raises a number of interesting and unanswered questions, but this study doesn’t go after any of them. Instead, it tells us what we already know from humans: males and females are of different but overlapping size, i.e., human height falls along a spectrum.
But human sex doesn’t.