Zachary Elliott
@zaelefty • 52,355 subscribers
Science educator in the biology of sex. Founder of @PdxInstitute. Author of four books. Producer of educational animations, articles, and books.
Videos
A biological anthropologist Dr. Michael P. Masters just claimed on Joe Rogan that human sex change is possible because of a disorder where "females turn into males at puberty." He makes 7 false claims. Let's break it down. 1. He first claims, "We all start out as females." No, we all start genetically sexed and physically undifferentiated, with bipotential gonads, the primordial genital ducts for both sexes, and a cloaca (Wolpert et al, 2019). Note these are not female gonads or genitalia. Around the 6th week, genetics differentiate our neutral gonads into testes OR ovaries, and then genetics and hormonal signaling from the gonad eliminates one duct and builds the other one. Thus, sex development begins physically neutral and diverges down EITHER the male OR female path due to genetics (Rey et al. 2020). 2. He claims "A population on a pacific island grow up as female until puberty transforms some of them into males." Certain isolated island communities have high rates of what's called 5-alpha reductase deficiency (5-ARD), a MALE ONLY disorder of sex development that causes a male fetus (with testes) to not produce enough DHT, the hormone required for the development of the male's penis, scrotum, and testicular descent (Kumar et al, 2022). At puberty, the surge of testosterone FROM THEIR TESTES causes masculinization of their external genitalia and body, with some descent of the testes and development of the penis and scrotum. These males were NEVER females. They are born as males WITH TESTES with underdeveloped external genitals. 3. He claims, "The population is insensitive to DHT." No, those with the disorder have an enzyme deficiency, where they cannot PRODUCE enough of the enzyme to convert testosterone into DHT. Their bodies can respond to DHT normally. It's that they cannot produce enough of it to guide the external genital development of the male fetus (Kang et al. 2014). 4. He claims, "Their ovaries descend and become testes at puberty." No, they never had ovaries. Like all other males, males with 5-ARD have the SRY gene. This triggers their bipotential gonads to differentiate into testes (Kashimada & Koopman, 2010). This does not happen during puberty. This happens at 6 weeks gestation. Just because their testes may not descend does not make them ovaries. 5. He claims, it's called "pseudohermaphroditism." No, it's called 5-alpha reductase deficiency. Medicine has abandoned the use of the term pseudohermaphroditism since early 2000s because it obscures the actual reality of these rare conditions, and is "scientifically specious and clinically problematic" (Dreger et al. 2005). 6. He claims, "They turn into the opposite sex." No, they start out in utero as males and remain as males for life. Just because they were not able to fully develop their external genitals does not make them females. They are males with testes who could not fully develop the penis and scrotum due to lack of DHT. Humans cannot change sex. We are gonochoric--a species whose individuals are male or female for life, determined by their genetics (Holub & Shackelford.) 7. He claims, "It doesn't do anything. Natural selection wouldn't select against it. It's just weird." No, the disorder causes many issues with male fertility. First, low DHT can impair the growth and differentiation of sperm cells and the growth of the prostate, causing them to have a prostate that is 1/10th the healthy size. Small prostates mean that semen volumes are low, harming sperm transport and motility. Second, undescended testes can also disrupt the careful balance of temperature for sperm creation (Kang, Imperato-McGinley, Zhu, & Rosenwaks, 2014). Parroting false claims about these rare disorders like 5-ARD hurts the public's understanding of these conditions, makes people believe falsehoods about human biology, and can harm the evidence-based treatment of the individuals who have these disorders. Scientific sources for further reading: Wolpert, L., Tickle, C., & Martinez Arias, A. (2019). Principles of Development (6th ed.). Oxford University Press. Rey, R., Josso, N., Racine, C. (2020). Sexual differentiation. In: Endotext. South Dartmouth, MDText, Inc. Kumar, G., & Barboza-Meca, J. J. (2022). 5-Alpha-Reductase Deficiency. In StatPearls. StatPearls Publishing. Kang, H., Imperato-McGinley, J., Zhu, Y.-S., & Rosenwaks, Z. (2014). The effect of 5a-reductase-2 deficiency on human fertility. Fertility and Sterility, 101(2), 320–326. Kashimada, K., Koopman, P. (2010). Sry, the master switch in mammalian sex determination. Development, 137. Dreger, A. D., Chase, C., Sousa, A., Gruppuso, P. A., & Frader, J. (2005). Changing the nomenclature/taxonomy for intersex: A scientific and clinical rationale. Journal of Pediatric Endocrinology and Metabolism, 18(8), 729–733. Holub, A., Shackelford, T. (2021). Gonochorism. Encyclopedia of Animal Cognition and Behavior. Springer.
Zachary Elliott229,327 Aufrufe • vor 7 Monaten
Imane Khelif is in the news once again. He himself now admits he has a Y chromosome and the SRY gene. This, along with the other pieces of evidence, reinforce that he has a male DSD called 5-ARD. See our animation on the biology of 5-ARD and our sex development chart.
Zachary Elliott89,883 Aufrufe • vor 5 Monaten
Even when height and weight are matched between male and female athletes, the male will outperform the female. The reason for this is due to musculoskeletal advantages caused by sex. Listen as I discuss the incredible data. Interview with OutspokenSamantha.
Zachary Elliott26,756 Aufrufe • vor 2 Monaten
Why the definition of sex J.K. Rowling posted is scientifically and biologically sound.
Zachary Elliott14,194 Aufrufe • vor 1 Monat
Protecting the female sports category is simple: a one-time cheek swab for the SRY gene using Polymerase Chain Reaction (PCR). SRY = indicates male No SRY = indicates female Scientifically precise, accurate, and non-invasive. Rare conflicting cases can be evaluated further.
Zachary Elliott15,033 Aufrufe • vor 2 Monaten
We do not all begin female, We begin genetically sexed, and our reproductive anatomy is undifferentiated up until the 6th week, when genetics trigger differentiation of our bipotential gonads into testes or ovaries. See our animation which explores this incredible embryology.
Zachary Elliott27,230 Aufrufe • vor 6 Monaten
