A Response to SciAm’s Stop Using Phony Science
Description
The Scientific American blog article “Stop Using Phony Science to Justify Transphobia” is another piece which uses the complexities of sex development and the diversity of sex differences to argue that sex is not binary. Let's analyze the argument with peer-reviewed science.
Sources
[1] Inoubli, A., et al. (2011). Karyotyping: Is It Worthwhile in Transsexualism? The Journal of Sexual Medicine, 8(2).
[2] Sax, L. (2002). How common is lntersex? A response to Anne Fausto-Sterling. Journal of Sex Research.
[3] Gilbert, SF. (2000). Chromosomal sex determination in mammals. Developmental Biology, 6th edition. Sunderland (MA), Sinauer Associates.
[4] Kimball, J. (2020). Sex chromosomes. LibreText.org.
[5] Kashimada, K., Koopman, P. (2010). Sry, the master switch in mammalian sex determination. Development, 137.
[6] Matson, C., et al. (2011). DMRT1 prevents female reprogramming in the postnatal mammalian testis. Nature.
[7] Lehtonen, J., Parker, G. (2014). Gamete competition, gamete limitation, and the evolution of two sexes. Molecular Human Reproduction, 20(12).
[8] Luo, Z., et al. (2019). Gender identification of human corticol 3-D morphology using hierarchical sparsity. Frontiers in Human Neuroscience.
[9] Ellis, L. (2011). Identifying and explaining apparent universal sex differences in cognition and behavior. Personality and Individual Differences, 51.
[10] Schmitt, D. (2016). Sex and gender are dials, not switches. Psychology Today.
[11] Lehtonen, J., Parker, G. (2014).
[12] Hayward, A., Gillooly, J. (2011). The cost of sex: Quantifying energetic investment in gamete production by males and females. PLoS ONE, 6(1).
[13] Marinov, GK. (2020). In humans, sex is binary and immutable. Academic Quest.
[14] Epelman, M., et al. (2005). Anisogamy, expenditure of reproductive effort, and the optimality of having two sexes. Operations Research, 53(3).
Transcript
The Scientific American blog article 'Stop Using Phony Science to Justify Transphobia' is another piece which uses the complexities of sex development and the diversity of sex differences to argue that sex is not binary. Let's analyze the argument with peer-reviewed science.
The author writes that three subjects help explain the transgender experience:
(1) Genetics (the instructions for biological processes)
(2) Neurobiology (the structure and connections of the brain)
(3) Endocrinology (the influence of hormones on the body)
The biological experience of trans individuals, like everyone else, can be affected by these three variables.
We'll start with PART ONE--Genetics:
The author writes, "Nearly everyone in middle school biology learned that if you've got XX chromosomes, you're a female; if you've got XY, you're a male." The author claims this is a tired simplification. But even with the existence of other chromosomal arrangements, is the XX and XY model a simplification?
First, atypical karyotypes (like X or XXY) are unrelated to trans identities, since trans individuals almost always have typical XX or XY karyotypes. We know this because karyotype analysis has been performed in research studies for transgender individuals. In one study, conducted with over 300 trans individuals, 97.55% had typical karyotypes of XX or XY, matching their birth sex. Only 3 out of 368 had Klinefelter syndrome.[1] Such studies show us that using chromosomal anomalies to explain trans experience is ignorant or dishonest.
Second, 99.98% of births are unambiguously male or female.[2] Even in cases of chromosomal anomalies like X or XXY, the fetus still develops a reproductive system organized to support ova (in X cases) or a system organized to support sperm (in XXY cases).
The reason why chromosomal anomalies still produce a female or male is due to the activation of the SRY gene (usually found on the short arm of the Y chromosome). If the SRY gene is present, functional, and active, it initiates a complex set of gene cascades causing male development.[3] Fetuses with only one X chromosome do not have the SRY gene and develop as females, whereas fetuses with XXY chromosomes do have the SRY gene and develop as males. This genetic system is so consistent that, even in cases of XXX or XXXY, the fetus still develops as a female or male, respectively.[4]
The author then discusses rare congenital medical conditions of the reproductive tract (known as Differences in Sex Development, or DSDs) to argue against the sex binary: "XX individuals could present with male gonads. XY individuals can have ovaries," they write. Those unfamiliar with sex development might be wondering how these variations occur. Simple: the activation or inactivation of the SRY gene. For XX individuals with testes, the SRY gene is present on one of the X chromosomes, and this results in male development. And for XY individuals with ovaries, the SRY gene is not activated, and this results in female development. Thus, sex is indeed largely determined by the activation or inactivation of the SRY gene.[5] Chromosomal, hormonal, and genital variations still produce males and females, not something between, nor a third sex.
So, you might ask, what do medical conditions like DSDs have to do with trans individuals, who almost always have typical chromosomes and develop the reproductive systems associated with those karyotypes? The answer is this: DSDs/intersex conditions do not relate to trans identities, nor do they cause one to be transgender.
PART TWO--Neurobiology:
Next, the author uses neuroscience research to argue that male and female cannot be clearly defined. They write, "A half century of empirical research has repeatedly challenged the idea that brain biology is simply XY = male brain or XX = female brain."
It is true that there is no single "male brain" or "female brain," but rather a mosaic of traits, where some patterns are seen more in males, some more in females, and many in both males and females--similar to the variation in our faces. But this variation in brain differences does not mean male and female cannot be clearly defined: we define sex through one of two evolved reproductive anatomies which develop for the production of either sperm or ova.[7] Despite claims to the contrary, there are average differences in the brain within and between males and females that, when aggregated together, allow us to predict someone's sex with up to 97% accuracy.[8] This is specifically done through analyzing the overall morphology of the cerebral cortex.
It is also true that trans individuals may have specific structures in the brain that are more similar to structures typically seen in the opposite sex. As the author mentions, some specific regions in gay men are similar to straight women. But these similarities do not alter one's sex. It simply means that one might have specific structures that are atypical, produced from a complex mix of biological and environmental processes.
PART THREE--Hormones:
Finally, the author uses hormone levels to 'disprove' the sex binary. They write: "But like all things biology, hormones cannot be limited to the idea of 'estrogen = female and testosterone = male.' "While males and females are both exposed to testosterone and estrogen, these hormone levels, like differences in the brain, exist as bimodal distributions, an average for males and an average for females.[9] Variance in hormones, even extreme variance, does not disprove the sex binary. For example, a male who has less T than the average male does not become 'less male' or 'more female.' He is still a male, as his body is organized to support small gametes.
In conclusion, you may notice a pattern in all three aspects: genetics, neurobiology, and endocrinology. In all three categories, variation does not mean sex is on a spectrum, but rather, that sex-related traits are on a spectrum within each sex. Sex differences exist as two distributions--a separate distribution for males and a separate one for females. There is variation of hormone production, brain structure, and external appearance, but this does not make a 'sex spectrum.' Rather, it makes a spectrum of variation in anatomy and physiology within males and within females.[10] The reason why we can place traits such as hormone levels on bimodal distributions is BECAUSE of the sex binary. Because there are only two gametes of differing size, there are only two sexes.[11]
The author presents basic scientific facts about the variation of sex-related traits. Where they go wrong is arguing that variation of genes, brain structure, and hormones proves that male and female cannot be reliably defined. "The science is clear and conclusive," they write, "sex is not binary, transgender people are real."
And yet, the truth is sex IS binary. The existence of trans people does not disprove this model, nor does not invalidate them. Rather, trans individuals represent the variation in biology, identity, and expression found within the sex binary. We don't have to deny the fundamental reality of sex to accept them or their experiences.
I'm Zach, for the Paradox Institute.
END
© 2020 Zachary A. Elliott, All Rights Reserved.