Description

Our full response to "Sex and Sensibility" by Forrest Valkai, analyzing his claims in detail with evolutionary and developmental biology. As an educational tool, we spend four hours separating truth from falsehood in every point he makes .

Timestamps Below

0:00:00 – Intro

0:00:18 – Forrest’s video

0:01:30 – Importance of taxonomy

0:05:36 – Using "male" and "female" out of convenience

0:11:37 – Biological systems have function

0:14:12 – Misusing the terms dioecious and monoecious

Muyle, A., et al. (2021). Dioecy is associated with high genetic diversity and adaptation rates in the plant genus Silene. Molecular Biology and Evolution, 38(3), 805-818.

Lehtonen, J. (2017). Gamete Size. Encyclopedia of Evolutionary Psychological Science.

Holub, A., Shackelford, T. (2021). Gonochorism. Encyclopedia of Animal Cognition and Behavior. Springer.

0:17:30 – Conflating sex determination with the definition of sex

Eggers, S., Sinclair, A. (2012). Mammalian sex determination: insights from humans and mice. Chromosome Res, 20.

Bachtrog D, Mank JE, Peichel CL, Kirkpatrick M, Otto SP, Ashman TL, et al. (2014). Sex Determination--Why So Many Ways of Doing It. PLoS Biol, 12(7).

Lehtonen, J., Parker, G. (2014). Gamete competition, gamete limitation, and the evolution of two sexes. Molecular Human Reproduction, 20(12).

0:21:20 – The infertility fallacy

Lehtonen, J. (2021). The legacy of Parker, Baker, and Smith 1972: gamete competition, the evolution of anisogamy, and model robustness. Cells, 10(573).

Goymann, W., Brumm, H., Kappeler, P. (2022). Biological sex is binary, even though there is a rainbow of sex roles. BioEssays, 45(3).

Neander, K. (1991). The teleological notion of 'function.' Australasian Journal of Philosophy, 69(4), 454-468.

0:29:50 – Conflation of isogamy with anisogamy

Lehtonen, J., Kokko, H., Parker, GA. (2016). What do isogamous organisms teach us about sex and the two sexes? PTBS, 371(1706), 1-12.

Perrin, N. (2011). What uses are mating types? The developmental switch model. Evolution, 66(4), 947-956.

Lehtonen, J., Parker, G. (2014). Gamete competition, gamete limitation, and the evolution of two sexes. Molecular Human Reproduction, 20(12).

0:31:49 – Conflation of sex with sexual behavior

Griffiths, P. (2020). The existence of biological sex is no constraint on human diversity. Aeon.

Long, X., et al. (2022). Independent evolution of sex chromosomes and male-pregnancy related genes in two seahorse species.

Whittington CM, Griffith OW, Qi W, Thompson MB, Wilson AB. (2015). Seahorse brood pouch transcriptome reveals common genes associated with vertebrate pregnancy. Mol Biol Evol. 32, (3114–3131).

0:33:16 – Conflation of literal gamete size with sexes

Lehtonen, J., Parker, G. (2014). Gamete competition, gamete limitation, and the evolution of two sexes. Molecular Human Reproduction, 20(12).

da Silva, J. (2018). The evolution of sexes--a specific test of the disruptive selection theory. Ecology and Evolution, 8, 207-219

Lehtonen, J. (2021). The legacy of Parker, Baker, and Smith 1972--gamete competition, the evolution of anisogamy, and model robustness. Cells, 10(573).

0:34:52 – Claiming that large sperm makes the male-female gamete distinction arbitrary

Gardiner, J. (2016). The bigger, the better. Nature Evolution, 533(476).

Hill, A., Eisenberg, D. (2016). The long and short of it: new insights on sperm length help demystify the complexities of sexual selection. Asian Journal of Andrology, 18(6): 902-903.

Anderson M, Dixson A, Dixson A. (2006). Mammalian sperm and oviducts are sexually selected: evidence for co-evolution. J Zool, 270, 682–6.

0:40:40 – Clarifying the difference between dioecious and gonochorism

Muyle, A., et al. (2021). Dioecy is associated with high genetic diversity and adaptation rates in the plant genus Silene. Molecular Biology and Evolution, 38(3), 805-818.

Holub, A., Shackelford, T. (2021). Gonochorism. Encyclopedia of Animal Cognition and Behavior. Springer.

Pla, S., Benvenuto, C., Capellini, I., et al. (2022). Switches, stability, and reversals in the evolutionary history of sexual systems in fish. Nature Communications, 13.

0:44:30 – Claiming that the idea we’re born male or female is deeply flawed

Sax, L. (2002). How common is intersex? A response to Anne Fausto‐Sterling. Journal of Sex Research, 39(3).

van Zoest, M., et al. (2019). Sex assignment and diagnostics in infants with ambiguous genitalia – a single-center retrospective study. Sexual Development, 13(3).

Avise, J. (2011). Hermaphroditism: a primer on the biology, ecology, and the evolution of dual sexuality. Columbia University Press.

Scharer, L. (2017). The varied ways of being male and female. Molecular Reproduction & Development, 84.

Dreger, A., Chase, C., Sousa, A., et al. (2005). Changing the nomenclature-taxonomy for intersex--A scientific and clinical rationale. Journal of Pediatric Endocrinology & Metabolism, 18, 729-733.

Rosenfield, K. (2018). Hermaphrodite. Encyclopedia of Animal Cognition and Behavior.

0:55:54 – Using bilateral gyndandromorphs to disprove the sex binary

Fusco, G., Minelli, A. (2023). Descriptive versus causal morphology: gyndandromorphism and intersexuality. Theory in Biosciences, 142(1), 1-11.

0:58:42 – Using Ovotesticular DSD in humans

Baetens, D., et al. (2017). NR5A1 is a novel disease gene for 46,XX testicular and ovotesticular DSD. Genetics in Medicine, 19(4).

Dayal, M. (2017). Ovotesticular Disorder of Sex Development. Medscape.

Ledig, S., et al. (2012). Partial deletion of DMRT1 causes 46,XY ovotesticular disorder of sexual development. European Journal of Endocrinology, 167.

Matsui, F., et al. (2011). Long‐term outcome of ovotesticular disorder of sex development. International Journal of Urology.

Scarpa, MG., et al. (2017). 46,XY ovotesticular disorders of sex development, a therapeutic challenge. Pediatric Reports, 9.

1:04:15 – Typical sex development is inaccurate according to Forrest

Rey, R., Josso, N., Racine, C. (2020). Sexual differentiation. In: Endotext. South Dartmouth, MDText, Inc.

1:07:18 – Sex differences in gene expression exist before gonadal differentiation

Ngun, T., et al. (2010). The genetics of sex differences in brain and behavior. Frontiers in Neuroendocrinology, 32.

1:10:01 – The myth we all start out as female

Rey, R., Josso, N., Racine, C. (2020). Sexual differentiation. In: Endotext. South Dartmouth, MDText, Inc.

Estermann, M., Smith, C. (2020). Applying single-cell analysis to gonadogenesis and DSDs. International Journal of Molecular Sciences, 21(6614).

1:12:27 – Sex reversal in mice under experimental conditions

Ottolenghi, C., et al. (2007). Loss of Wnt4 and Foxl2 leads to female-to-male sex reversal extending to germ cells. Human Molecular Genetics, 16(23), 2795-2804.

Eggers, S., Sinclair, A. (2012). Mammalian sex determination: insights from humans and mice. Chromosome Res, 20.

Weber, C., Capel, B. (2022). Sex reversal. Current Biology, 28(21): R1234-R1236

McClaren, A., et al. (1995). Germ cells and germ cell sex. Phil Trans R Soc Lond B, 350, 229-233.

Kocer, A., Reichmann, J., Best, D., Adams, I. (2009). Germ cell sex determination in mammals. Molecular Human Reproduction, 15(4), 205-213.

1:22:01 – Female wallabies born without egg cells develop testes

Renfree, M., Short, R. (1988). Sex determination in marsupials: evidence for a marsupial-eutherian dichotomy. Phil Trans R Soc Land, 322, 41-53.

Renfree, M., et al. (1995). The marsupial male: a role model for sexual development [and discussion]. Philosophical Transactions of the Royal Society B, 350, 243-251.

Renfree, M., Shaw, G. (2001). Germ cells, gonads, and sex reversal in marsupials. The International Journal of Developmental Biology, 45, 557-567.

Weber, C., Capel, B. (2022). Sex reversal. Current Biology, 28(21): R1234-R1236

1:25:54 – Everyone has the genes to make testes or ovaries

Warr, N., et al. (2012). The molecular and cellular basis of gonadal sex reversal in mice and humans. WIREs Dev Bio, 1.

Bashamboo, A., et al. (2017). Anomalies in human sex determination provide unique insights into the complex genetic interactions of early gonad development. Clinical Genetics, 91, 143-156.

Witchel, S. (2018). Disorders of sex development. Best Practice and Research in Clinical Obstetrics and Gynecology, 48.

1:32:07 – Genetic errors that can occur, causing sex reversal

Lavery, R., et al. (2011). XY Sox9 embryonic loss-of-function mouse mutants show complete sex reversal and produce partially fertile XY oocytes.

Li, T., et al. (2014). 46,XX testicular disorder of sexual development with SRY-negative caused by some unidentified mechanisms: a case report and review of the literature. BMC Urology, 14.

Yue, F., et al. (2019). Molecular cytogenetic analysis and genetic counseling: a case report of eight 46,XX males and a literature review. Molecular Cytogenetics, 12.

1:33:04 – Conflation of sex determination mechanisms with sex

Terao, M., et al. (2022). Turnover of mammal sex chromosomes in the SRY-deficient Amami spiny rat is due to male-specific upregulation of SOX9. PNAS Genetics, 119(49).

Ioannidis, J., et al. (2021). Primary sex determination in birds depends on DMRT1 dosage, but gonadal sex does not determine adult secondary sex characteristics. PNAS, 118(10).

Woodward, D., & Murray, J. (1993). On the effect of temperature-dependent sex determination on sex ratio and survivorship in crocodilians. Proceedings: Biological Sciences, 252(1334), 149-155.

Cornejo-Paramo, P., et al. (2020). Sex determination systems in reptiles are related to ambient temperature but not to the level of climatic fluctuation. BMC Evolutionary Biology, 20(103).

1:38:43 – Hormones regulate sex differentiation of the internal and external genitalia

Witchel, S. (2018). Disorders of sex development. Best Practice and Research in Clinical Obstetrics and Gynecology, 48.

Jones, R., Lopez, K. (2014). Human Reproductive Biology, 4th edition. Elsevier.

1:45:29 – We all have testosterone and estrogen in our bodies

Handelsman, D., et al. (2018). Circulating testosterone as the hormonal basis of sex differences in athletic performance. Endocrine Reviews, 39(5), 803-829.

Clark, R., et al. (2019). Large divergence in testosterone concentrations between men and women: Frame of reference for elite athletes in sex-specific competition in sports, a narrative review. Clinical Endocrinology (Oxford), 90(1), 15-22.

Hilton, E., Lundberg, T. (2020). Transgender women in the female category of sport: Perspectives on testosterone suppression and performance advantage. Sports Medicine, 51(2), 199-214.

Marrocco, J. McEwen, B. (2016) Sex in the brain, hormones and sex differences. Dialogues in Clinical Neuroscience, 18(4).

1:51:25 – Forrest then claims that “hormones don’t actually do anything”

Sturmhofel-Hiller, S., Bartke, A. (1998). The endocrine system. Alcohol Health and Research World, 22(3), 153-164.

McEwen & Milner. (2017). Understanding the broad influence of sex hormones and sex differences in the brain. Journal of Neuroscience Research, 95.

1:54:13 – Androgen Insensitivity Syndrome

Lanciotti, L., et al. (2019). Different clinical presentations and management in complete androgen insensitivity syndrome (CAIS). International Journal of Environmental Research and Public Health, 16(7).

Wang, S., et al. (2009). Androgen receptor roles in spermatogenesis and fertility: Lessons from testicular cell-specific androgen receptor knockout mice. Endocrine Reviews, 30(2), 119-132.

Oakes, M., et al. (2008). Complete androgen insensitivity syndrome: a review. Journal of Pediatric and Adolescent Gynecology, 21(6).

Barros, B., et al. (2021). Complete androgen insensitivity syndrome and risk of gonadal malignancy: a systematic review. Annals of Pediatric Endocrinology & Metabolism, 26(1), 19-23.

2:01:03 – X-inactivation in typical XX females

2:03:07 – Not all genes activate

2:05:05 – Using sex determination in birds to claim male and female are arbitrary

Ioannidis, J., et al. (2021). Primary sex determination in birds depends on DMRT1 dosage, but gonadal sex does not determine adult secondary sex characteristics. PNAS, 118(10).             

2:06:20 – Temperature sex determination

Woodward, D., & Murray, J. (1993). On the effect of temperature-dependent sex determination on sex ratio and survivorship in crocodilians. Proceedings: Biological Sciences, 252(1334), 149-155.

Cornejo-Paramo, P., et al. (2020). Sex determination systems in reptiles are related to ambient temperature but not to the level of climatic fluctuation. BMC Evolutionary Biology, 20(103).

2:08:19 – Conflation of variation with disorder

2:12:48 – You need more genetic networks outside X and Y chromosomes to develop as a male or female

Leon, N., Reyes, A., Harley, V. (2019). Differences of sex development--the road to diagnosis. Lancet Diabetes Endocrinology.

2:15:02 – Claiming there is no standard template for male vs female development

Witchel, S. (2018). Disorders of sex development. Best Practice and Research in Clinical Obstetrics and Gynecology, 48.

2:18:54 – Forrest claims that unless you’ve gotten your DNA analyzed, we can’t know your sex.

Maeda et al (1991). A cytogenetic survey of 14,835 consecutive liveborns. The Japanese Journal of Genetics, 36(1), 117-129

Hamerton et al (1975). A cytogenetic survey of 14,069 newborn infants. I. Incidence of chromosome abnormalities. Clinical Genetics, 8(4), 223-243.

Nielsen & Sillesen (1975). Incidence of chromosome aberrations among 11,148 newborn children. Human Genetics, 30(1), 1-12.

2:22:30 – More than enough variations on the sex chromosomes alone…

2:25:41 – Conflation of complex genetics with sex itself

2:31:09 – Forrest claims we cannot say that girls are XX

2:33:42 – Defining gender

2:37:27 – Claiming that masculinity and femininity do not really mean anything

2:42:22 – Conflating dimorphic variation with sex itself

2:43:58 – Using hyenas to argue sex itself is a spectrum

Cunha, G., et al. (2005). The ontogeny of the urogenital system of the spotted hyena. Biology of Reproduction, 73, 554-564.

2:47:20 – Male bats that can lactate

Houghton, M. (2023). The incredible milk-producing male bat. Bat Conservation International.

2:50:00 – Conflating diversity of sex roles with sex

Scharer, L., Rowe, L., Arnsqvist, Q. (2012). Anisogamy, chance, and the evolution of sex roles. Trends in Ecology and Evolution, 27(5), 260-264.

Scharer, L. (2017). The varied ways of being male and female. Molecular Reproduction & Development, 84.

2:54:15 – Neuroscience Section

See here: https://www.youtube.com/watch?v=ToTLj56JQY4

2:54:57 – Describing traits, ignoring function and statistics

2:56:50 – Forrest claims that people with developmental disorders make sex undefinable

3:03:13 – Forrest claims you can have more than one penis or vagina

Correction: This can happen. In males, diphallia or penile duplication is an extremely rare congenital anomaly. It occurs once in every 5.5 million live births of males. There is also uterus didelphys, which results in a split or duplicate uterus in females and can also involve the vaginal canal. These conditions are sex-specific, can often result in infertility, have other associated congenital anomalies, and are not evidence that sex is a spectrum.

Thank you for all your feedback and notes!

Diphallia: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3870645/

Uterus didelphys: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8777336/

Lee, P., et al. (2016). Global disorders of sex development--Update since 2006. Hormone Research in Pediatrics, 85, 158-180.

Dreger, A. (2009). Both sets of genitals…not. AliceDreger.

3:04:55 – It’s easier to claim sex is a spectrum

3:07:40 – Without genetic tests, you have “no idea where you land.”

Maeda et al (1991). A cytogenetic survey of 14,835 consecutive liveborns. The Japanese Journal of Genetics, 36(1), 117-129

Hamerton et al (1975). A cytogenetic survey of 14,069 newborn infants. I. Incidence of chromosome abnormalities. Clinical Genetics, 8(4), 223-243.

Nielsen & Sillesen (1975). Incidence of chromosome aberrations among 11,148 newborn children. Human Genetics, 30(1), 1-12.

3:09:43 – Saying that boys are XY and that they must act a certain way is dangerous

3:17:54 – Conflation of sexual orientation with gender dysphoria

Burke, S., Manzouri, A., Savic, I. (2017). Structural connections in the brain in relation to gender identity and sexual orientation. Scientific Reports, 7.

3:18:59 – Gender dysphoria is a mental disorder; atypical sexual orientation is not

Frew, T., et al. (2021). Gender dysphoria and psychiatric comorbidities in childhood: a systematic review. Australian Journal of Psychology, 73(3), 255-271.

3:36:48 – Conflation of freedom of expression with violation of rights

3:39:52 – Forrest claims he barely scratched the surface

3:40:50 – Summarizing Forrest’s major errors

3:44:18 – Conflation of gender dysphoria with being trans

3:46:05 – Gish-gallop of sources