Are There More Than Two Human Sexes? (A Response to SciShow)

SciShow's 'There Are More Than Two Human Sexes' uses DSDs to claim that sex is more complicated than male and female. Let's explore what they mean.

Transcripts, sources, and membership at:

Sources:
[1] Green, H. (2019). There Are More Than Two Human Sexes. SciShow, YouTube.
[2] National Health Service. (2019). Differences in sex development. NHS.
[3] Lehtonen, J., Parker, G. (2014). Gamete competition, gamete limitation, and the evolution of two sexes. Molecular Human Reproduction, 20(12).
[4] Czaran, T., Hoekstra. R. (2004). Evolution of sexual asymmetry. BMC Evolutionary Biology, 4(34).
[6] Gilbert, SF. (2000). Chromosomal sex determination in mammals. Developmental Biology, 6th edition. Sunderland (MA), Sinauer Associates.
[7] Kashimada, K., Koopman, P. (2010). Sry, the master switch in mammalian sex determination. Development, 137.
[8] NIH. (2020). Androgen insensitivity syndrome. Genetics Home Reference, National Library of Medicine.
[9] NIH. (2020). Swyer syndrome. Genetics Home Reference, National Library of Medicine.
[10] Anik, A., et al. (2013). 46,XX Male DSD: A Case Report. Journal of Clinical Research in Pediatric Endocrinology, 5(4).
[11] Dumic, M., et al. (2008). Report of Fertility in a Woman with a Predominantly 46,XY Karyotype in a Family with Multiple Disorders of Sexual Development. The Journal of Clinical Endocrinology and Metabolism, 93(1), 182-189.
[12] NIH. (2020). 21-hydroxylase deficiency. Genetics Home Reference, National Library of Medicine.
[13] NIH. (2020). Persistent Mullerian Duct Syndrome. Genetics Home Reference, National Library of Medicine.
[14] Wilson, G. (2013). Third sex redux. Intersex Human Rights Australia.
[15] Cox, P., Togashi, T. (2011). The Evolution of Anisogamy, A Fundamental Phenomenon Underlying Sexual Selection.
[16] Schmitt, D. (2017). Sex and Gender are Dials (Not Switches), Psychology Today.

[leemoore]

The analysis in the video of Complete Androgen Insensitivity Syndrome is incorrect. Or rather the analysis is correct, ie that CAIS shows the independence of the SRY gene and androgen receptors, but the conclusion - that people with CAIS are female, is wrong.

People with CAIS have (internal) testes, not ovaries, because they have the SRY gene. That makes them male. Their testes produce testosterone (the other function of testes apart from sperm production) but since their other non SRY related genes produce non functional androgen receptors, their body plans, that is to say their body plans downstream from the gonads, develop as if they were female. Hence to all outward appearances, they look like females. Their secondary sexual characteristics are female, though in most cases there will be deviations fron normal female development, eg because of the partial anti-Mullerian effects of the testes. It should be noted that not all people with CAIS have the same genetic abnormality, and so the precise outcome of the Mullerian and Wolfian battle can vary in different cases. But in all cases, they're not female, because they have testes.

Their testes only produce immature sperm cells, non functional sperm.

For social purposes, it's perfectly reasonabe for people with CAIS to live as if they were females, indeed until they don't start menstruating in puberty there may be no suspicion that they are actually male. But for biological purposes, they're male.

[MrSaywutnow]

Seven and a half minutes is an awful long time to say "no".

[KarmaPolice_]

I love SciShow and Hank Green, but I remember when I saw that video months ago thinking that they screwed it by claiming that there are more than two sexes. The information mentioned in the video itself isn't incorrect, but the conclusion is. It's when trans activists use scientific studies regarding differences between male and female brains to claim that a trans person is trans because they have the brain of the opposite sex. I used to believe it myself, but after reading more papers and studies about this topic, I realised that there isn't really such a thing as a female brain or male brain, that these differences are not big or generalised enough to actually claim this, and that most of it is part of neuroplasticity: not something you are born with, but a matter of socialisation. The problem isn't the data, but the conclusions people make out of it.

[myriamm]

Thanks. I was really confused by the chromosome arguments and didn't know whether XX males were males or females. Thank you for clarifying this and reexplaining what sex is.

[crumblyduckling]

Thanks. No-one has yet shown evidence of a 'spegg', or 3rd gamete. No-one has proved it takes more than two humans to create offspring. Yet when I put this to a 'trans' advocate I was accused of 'harming others' & 'bigotry', i.e. 'no debate', just insults. One could arbitrarily pick any bodily variation, such as girls starting menstruation at different ages; some sailing through theirs while others have a hard time of it, & some women being more fertile than others - but it proves nothing; at the end of the day, they're all female. Proving no two humans are identical is an irrelevance. There are 2 sexes.

[Chuck_Nrris]

I am studying biology and I find this very interesting. For some reason sexes and genders are a super polarized topic, but science is just science. While you are right that the reproductive functions isnt exactly debatable, there are a lot of complex medical conditions that are in what we could call a grey zone. Some people have male chromosomes but a female anatonomy. Some people have sex development disorders which makes their sex hard to determine. And also the different genotypes codes for slightly different traits. Some genes are only inheritable trough the X chromosome and some only trough the Y chromosome. So if you have XXY for example, it is at the very least an interesting person to study. Sex studies is one thing though. You can be both male and female (hermafrodite) but there is no such thing as a third biological sex. Genders on the other hand is a whole different topic.

[toweypat]

Some people want to throw out any system of classification that doesn't cover everyone. But there will never be such a system, because an organism is too complex in its makeup, and development for every member of a group to fit neatly within. There are infinite number of ways that genes can malfunction, mutate, not appear at all, or otherwise throw something new at us that we have never seen. That doesn't mean classification is futile, just that we have to accept a degree of abstraction and uncertainty.

[Mortebianca]

You claim that Gonads should define someone's sex, yet consider CAIS as females despite them having testes.

You used a different definition right there, phenotype (genitals, to be precise). A contraddiction in regards to your other video in which you claimed that Genitals only matter in case of mixed gonads (both ovarian and testicular tissues mixed together).

You can't answer "I used Gametes, not Gonads" because CAIS don't produce Eggs either. So they are not female from your Gonad or Gamete classification, yet you consider them Females, despite their Gonad being 100% male, and chromosomes too.

[aodoemela]

Thank god someone has responded. Its a shame how this idea spreads like wildfire.

[angeldude]

I just checked and DSDs appear to be around 1 in 5000 births. That might not seem like a lot, but that's still 1.4 million people! People often point to low prevalence rates as a reason to discount certain experiences, seemingly without realizing that even those small rates can be a very big group of people when you remember that the total population is 7 billion.
And since people have been pointing to it, designing things assuming that everyone has 2 legs measurably affects not just people with fewer than 2 legs, but also people who do have both legs. And those people with fewer than two legs could be around 1.5%, or around 100 million people, which is comparable to the number of people with other marginalized conditions. Usually, accommodating people with those conditions also provides measurable benefits even to people without them.

[briiibriiibooo]

It’s obvious that when people claim “sex isn’t binary” they are stating that to justify that trans people as literally being what they identify as but that doesn’t follow logic! Even if sex wasn’t binary, the idea of claiming “ I identify as this therefore I am this” is not how reality works. There are more than two human races, but a person can not claim to be a race they are not simply by “identifying “ that they are that race! Great video 👌🏽

[patoloquend]

Great video. The gametes are very important aspect of the discussion. No one can produce both gametes at the same time and there is no third gamete. A third sex would have to reproduce in a way that breaks the male-female binary through a third gamete or something like human partenogenesis but that’s impossible.

[LavaCreeperPeople]

The name "women" implies that your the female sex. Like how the name "red" implies, you know, to the color red. You can't just say your a women but yet be a biological male, like how you can't just say your the color blue but yet be the color red. That is just confusion to society. Gender is not a social construct, it is more about being feminine or masculine because there is nothing wrong with being a feminine man, it just doesn't make you a women. Same with masculine women.

i cant believe adults even debate about this

[sharkofthecovenant]

Wow! I'm really impressed by how clearly this was explained. I did a search for "what is intersex" and the scishow video came up. I found it unconvincing, but terrifying at the same time because of how easily it could be used to manipulate people. I found THIS video when looking for a "response to scishow". I think the point about the definition of sex is so critical. In today's world it feels like very few people are left to name the scientific fact that sex is fundamentally inseparable from reproduction.

[mvmlego]

This video was a wasted opportunity.

1. Zach makes the same presentation error as Sci-Show by neglecting to use real-time citations--e.g. by displaying the index number of the source on-screen as he makes the relevant claim. Sources are useless if it's not clear which sources are intended to support which claims.

2. He doesn't apply his own definition of sex consistently. People with CAIS are often capable of producing sperm, but never capable of producing ova. Therefore, his claim and his graphic from 1:48 to 1:55, along with claims made elsewhere in the video, plainly imply that people with CAIS are male. Nevertheless, he classifies them as female (4:15).

3. He leans on invalid, identity politics rhetoric to shame people into joining his side. (This criticism is more applicable to some of his other videos, but he does this to a minor extent at 6:43.) It is not necessarily an insult to say that a given person is neither male nor female. Whether it's an insult depends entirely upon whether the speaker believes _a priori_ that being neither male nor female is a bad thing to be. It's clear that SciShow was trying to portray those conditions as being normal to the point of being mundane, rather than as something that justifies bullying or discrimination against people who have them.

[murphcallahan]

Beginning with the title, Green's video is misleading. Someone may watch it and come away with the idea that there are more than two sexes, even a spectrum of sexes, in nature. There are not. The order of nature has determined two sexes: XX and XY. Whenever this order is disrupted, it is due to a genetic malfunction. As the narrator calls it, a "mutation." A mutation is not part of the set order of things; it is, instead, an anomaly, or, as the narrator says, a "syndrome." A syndrome is not a good thing. It is not a third sex or a part of a "spectrum" of sexes. It is a genetic mistake, a genetic error, a mutation, and, as the narrator says, a recognized "syndrome." As the narrator says, these genetic mutations are harmful and require "medical care." > Someone may watch this video and conclude that, because they identify as something other than their sex, they probably are a "third sex" or a sex that is one part of a natural spectrum of sexes. But that would be a bad bet because the natural, undisturbed order is XX and XY. In any case, before people begin to assume anything, genetic studies need to be conducted on LGBTQ people to determine if genetic mutation is relevant to their self-conception.

[Schneemaa]

This channel really is a gem! Defining the sexes based on gametes makes so much sense.
I'm curious about your opinion of sex-change therapy/surgery, in particular whether you think it is possible to change one's biological sex

[brendanmurphy]

Thank you. Im a huge fan of scishow for dumbing things down. But I still could not understand that episode. This video helped explain things much more clearly.

[aigerimsam]

Very well made video. Although, the anti-trans group in the comments is really annoying. Human biology and psychology are still very much in the process of studying, so things aren't set in stone. There being only two sexes doesn't prove anything about gender, because there are still a lot of factors that haven't been studied yet. If you all are truly about facts, you should learn more and jump to conclusions less.

[denvan]

That was the last SciShow video I ever watched. I won’t abide political ideology that masquerades as scientific information.