Why are there two sexes? Real Science Chat: chromosome evolution
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- Опубліковано 5 сер 2024
- Another episode in my series exploring the evolution of our sex chromosomes! I hope you enjoy
Sources:
Czárán, T.L., Hoekstra, R.F. Evolution of sexual asymmetry. BMC Evol Biol 4, 34 (2004). doi.org/10.1186/1471-2148-4-34
Erika Kothe. Mating Types and Pheromone Recognition in the Homobasidiomycete Schizophyllum commune. Fungal Genetics and Biology. Volume 27, Issues 2-3 (1999) doi.org/10.1006/fgbi.1999.1129 Links to an external site..
Weeks, S. C., Sanderson, T. F., Zofkova, M., & Knott, B. (2008). Breeding Systems in the Clam Shrimp Family Limnadiidae (Branchiopoda, Spinicaudata). Invertebrate Biology, 127(3), 336-349. www.jstor.org/stable/40206204L... to an external site.
Lane, N., Martin, W. The energetics of genome complexity. Nature 467, 929-934 (2010). doi.org/10.1038/nature09486Links to an external site.
Johnson NA, Lachance J. The genetics of sex chromosomes: evolution and implications for hybrid incompatibility. Ann N Y Acad Sci. 2012 May;1256:E1-22. doi: 10.1111/j.1749-6632.2012.06748.x. PMID: 23025408; PMCID: PMC3509754.
I really enjoyed the video, though I do think it would be cool if you put the sources in the description section
Ayo, finally one of the first hundred to subscribe before an awesome science channel blows up! I'm here for the riiide!
Making my mark here, in case this channel blows up. The number of subscribers have already been climbing in the 80s every minute!
This is so interesting! I've wondered about this and the mitochondrial DNA thing, so it was great to stumble upon such a well-worded yet concise explanation. Thanks for teaching me something new today!
cool video, i wish you the best
Great video!
May the algorithm bless this knowledge!
Ignore any bigots in the comments, I think the balance of direct science communication and shutting down the ability of people to misrepresent what you said in gender essentialist ways was perfect. Great video!
uh?
Боже, спасибо алгоритмы, я над этим вопросом уже несколько лет нет-нет да задаюсь!
Автор красава, больше бы таких 💕
Ayyy, correct me if I'm wrong but I reckon that's the same riff from Allie Ward's podcast lol it's like part of the same cannon I dig it.
-J Petrie, like the dish but with an 'e' or the pterodactyl to a T
just wanted to make a note (it's not really important), in 3:30 you mentioned that in a binary reproductive system and individual would be able to mate with exactly half of the population, but in a lot of species there are more of one gender than the other (i could be wrong about this, but i believe even humans are slightly more like to be born male than female (emphasis on the slightly, i think it's less than 1%)).
Well presented points and general separation of nomenclature surrounding sex versus gender (Though I believe there was some mixing of the terms here and there), and good exploration of why our reproductive makeups are what they are^^
While I understand the point of your video is a macro-scale glance at why we are typically XX or XY, I think that discussing (Or addressing the existence of) chromosomal aneuploidy, mosaicism, the split between father's X and mother's X chromosomal activation in XX individuals, etc, would add a lot to the points raised here. Even insofar as researching common signs of aneuploidy and its positives/negatives in different configurations and their potential impacts on quality of life. On a wide angle approach to genetics in the interest of "Why does evolution trend us in this direction" I definitely agree with your assessment, I just think that something a lot of people lack a lot of information about is how much plasticity there actually is with how those sex chromosomes come to be expressed or passed down in some of the less-known cases.
Uhh no, I hadn't really wondered why there's only two human sexes. But it was cool to hear about it. I also really appreciated the disclaimer about sex and gender being different things since people conflate the two.
I'm also not sure that the different chromosome combos necessarily mean different sexes in all species. I think bees (idk what species) can be male or female via a few different chromosome setups each.
Got me in the first half ngl
Simply wrong. Sex, as in the male and female meaning, not the activity of reproduction IS ENTIRELY the same as gender. The root word for gender is that of generation/procreation. Since the particular role one performs in procreation is dictated by one's chromosomes (under normal developmental conditions) then sex and gender mean exactly the same thing. Also that's what the Oxford English Dictionary defines gender as - sex.
@@michaeldavison9808 From the Oxford Dictionary, the one you're referencing; "the fact of being male or female, ESPECIALLY WHEN CONSIDERED WITH REFERENCE TO SOCIAL AND CULTURAL DIFFERENCES, RATHER THAN DIFFERENCES IN BIOLOGY"
The caps isn't meant to be yelling, idk how to highlight the text on my phone.
Biological sex and social gender are two different things. One can decide to live their life as whatever gender they please. This will never change their biological sex even with surgeries and hormone therapies.
I will mention as well, just in case since this is the internet, I make no argument against making decisions about ones own gender or how one lives their private life. One can do whatever one wants as long as it doesn't hurt anyone.
Biological sex, or sex as in the condition of being genetically male or female =/= gender.
Interesting video but it seems like one gender hermaphroditic species should be able to have just as much variability as us...I'm not super sure how convinced I am that this is a satisfactory explanation. My best guess is that she "the lab mouse" is mostly right, but our ancient ancestors were hermaphroditic and then some of them mutated to lack either female sex organs or male sex organs, and since they had less organs that needed to be fuled by food they were less likely to starve to death and pass on their genes..
....also on a somewhat related note, frogs (and I think alligators too, not too sure) use temperature to determine gender not x and y chromosomes... to me this strongly indicates that the concept of two gendered species has actually arisen at least twice... so apparently this is something that evolution usually favors...
...and again I agree we are defiantly more than our evolution, evolution is a non-thinking, non-moral process, it cannot dictate what is good or bad, it merely is.
What about intersex?
if two sexes is optimal, then why does that crazy mushroom species not follow this rule? its pretty obvious why there are life species with only one sex, because cloning is just the most straight forward reproduction method, but what kind of environment is necessary to get a species to thrive with many more than two sexes?
also how does this relate to the definition of species in the first place. if the mushroom has so much variety of sexes, and many of them can only reproduce with specific others, how are they still all the same species?
well she's wrong. she fails to even understand what sex actually as you hear her right at the start. mushrooms don't have sexes. they have mating types.
Because evolution doesn't always follow what efficient, it just gets rid of what actively harms the species
However, in evolution it is way easier to repurpose or lose things than to gain new things. For example a hermaphroditic species might get mutations that result in them only having male or female parts, reproduce, the next generation inherits that and so on, which would be how something like that shrimp developed to have a male and two hermaphrodite sexes.
Evolution doesn't always slim down, but when it does, it rarely goes back which is why snakes have no legs and ostriches have 3 toes.
@@moocha4030 a mating type is just sexes but the gametes are all the same size, and the mating types of your parents is what determins your own mating type. Thats the difference.
You went from science to gender ideology and put them together these are separate convos for separate videos.
cool
While I think the disclaimer is important you hit the nail on the head with why sex determination is often "simple" or binary. Because it is actually optimal for diverse characteristics and mate selection. You don't just want a lot of variety but for that variety to be useful to the next generation. However sex differences (we're still talking physiological here) are very blurry and non-binary. Put it a different way many sex differences cross over into the other sex. Men have long hair and nipples, some women have more muscle than some men etc. In this sense your particular sex characteristics are a statistical phenomenon that are only obvious at the extremes (like in sports). While some sex characteristics that are obviously important to reproduction are more readily defined. But even with chromosomal sex determination there's still quite a few intersex people and that should really tell us something quite significant about evolution. The fact that evolution prefers simple states ends up creating much more variety.
Nice vid, but doesn't the "just one sex" case actually explains a "no sex at all" scenario? If everyone had both sets of organs, wouldn't a free-for-all, where everyone can mate with everyone, be even more beneficial?
Not necessarily, hermaphroditic species can fight with each other to be the impregnating one since the one that gestates the fertilized egg has to invest more of its bodily resources. For example, some snail species literally "sword fight" to piece their mating partner's oviducts. In these cases some individuals may just self-fertilize to opt out of putting in extra effort of fighting every mating partner they come across, which results in cloning.
Alternatively, some fish species that are hermaphroditic and mate through spawning may loose out from overproducing eggs, since they're larger cells that require more resources to generate. Hence, they'll be more competition between individuals to overproduce sperm, meaning during spawning season there might be disparaties between the amount of sperm vs eggs in the water. In this case, there would be countless inefficient reproductive events seeing as there would be not that many eggs to fertilize, and there's no gurantee that each individual can reproduce since each sperm "swarm" would have PLENTY of competition with other sperm swarms for the limited eggs. As such, there would be less overall genetic variance in a spawning population since not all individuals can successfully mate during each spawing event.
Asexual reproduction isn't the same thing as having only one sex tho. It's simply an unstable situation with a race of who's going to waste less energy while making baby.
Also leaving comment cuz I hope your channel will grow
Clearly, there’s an inequality in the sexes, where the female has the advantage, and the male is the subjugate, gender or sex, perhaps, expendable, alienatetable, therefore, could you please explain how these two genders came to evolve and why variability and diversity is obvious, but it doesn’t explain its origins😊
sex is the two reproductions roles. it just means big gamete(From female)+small gamete (from male) = baby. there's no other kinds.
That doesn't apply to things with mating types, and is unhelpful with hermaphrodites
Mating types don't have big vs small, and some species have multiple sizes of gamete, for example a kind of fly that has 5 different sexes (4 male, one female) each gamete a different size, however, one male sex actually has a larger gamete than the female sex does. Its not considered a female gamete though, because it has a tail, and is incompatible with the other male sexes in that fly species.
I know that you are talking about the binary nature of the X and y chromosome when you speak of sex throughout, and I appreciate that you brought up hormonal sex and gender.
However
I feel that your scripting was lacking.
As an intersexed chimera whom had a leak on my identity and a good half of my home towns young men trying to lynch me as such I found your script lacking, and every mention of two sexes a sharp reminder of the hatred, bigotry, and violence I delt with amd survived growing up.
2 base pairs, each with thier own dominance to expression leads to four possible sexes each with binary paring, shared embryonic sacks for fraternal twinning leads to 8, and then there is the ability to carry more then two X chromosomes without causing disorder and this was the point where my then newly pubescent mind got distracted from the genetic engineer from the nearest university by the frankly very attractive asstant but I did gather that those did additionally multiply the number of genetic sexes possible.
And each maintaining cross compatability with approximately 50% of the population and its a truly phenomenal amount of diversity we can achieve from just *two sexed chromosomes.*
Please, I know yoir channel is small now; you ended up in my recommendations. And I can see how this video could be fuel for further hatred and bigotry particularly with context removed as bigotry is want to do.
Two sexed chromosomes. That can express more just like binary numbers can count to the millions, all while maintaining that mythical binary compatibility.
That is terrifying and i hope you are ok now, i would try finding a domestic violence shelter to stay at
On the four combinations part, YY human is impossible as there isn't enough DNA in the Y chromosome to form a human, same goes for Y0 (singular Y chromosome)
Here's a look at the easy list of variation within human sex chromosomes:
X0
XX, XY
XXX, XXY, XYY
XYYY, XXYY, XXXY XXXX
^thats up to 4 chromosomes
Mixing science talk and social politics might not be the best idea,
unless the point is to discuss ideologies in the comment section then nvm.
other than that, nice video
I think adding one personal musings on how to incorporate quite abstract scientific concepts into your life is relevant, especially in a world where people are using misinformation or misrepresentation of science to cause harm to people. If you are talking about racial IQ gaps for instance, because of 'scientific' racism, it's your duty to mention that the scientific knowledge base bears out that these changes are most likely environmental, and have been closing as racial inequality has been worked on. Likewise, the scientific existence of hormonal sex as distinct from chromosomal sex, and the further distinction of gender from sex are important things to bring up, because people will often cherry pick narrow parts of the scientific knowledge base to misrepresent science in support of a gender essentialist ideology. It's your duty in the name of scientific accuracy to communicate scientific concepts in a way that doesn't feed the fire of bad faith actors.
trans people exist, get over it
The fact that genderqueer people exist isn't political
@@perplexedon9834 Personal musings are not facts, they are opinions.
To take your example if you are explaining racial IQ gaps you better also provide evidence of environmental changes affecting it to also support it.
Otherwise your are just trying to limit different perspectives which might lead to innovation in the future.
Also the fact that you commented twice about this topic was exactly my previous point.
@@cyfangz9238 your reading comprehension doesn't seem great. My statement that person musings on how to apply finds to your life are relevant was independent from my statement that there is a duty to anticipate the way bigots will try to misrepresent science.
If you aren't university educated in reading and critically appraising academic studies, you may not get much out of my sources, but I can basically give you as many as you'd like. Here's some reading if you would rather try to critically read research, otherwise feel free to just say "lol nerd" if you don't care about the truth.
The Flynn effect is the observed increase in IQ when applying tests from previous decades to the modern population. This indicates that IQ tests do not measure general, genetic intelligence, because there is no plausible mechanism for successive generations in such a short span of time to be genetically improved. To quote the reference meta-analysis "favourable social multiplier effects and effects related to economic prosperity appear to be responsible for observed differences in the Flynn effect accross intelligence domains"
Pietschnig, J., & Voracek, M. (2015). One Century of Global IQ Gains: A Formal Meta-Analysis of the Flynn Effect (1909-2013). Perspectives on Psychological Science, 10(3), 282-306. doi.org/10.1177/1745691615577701
Here is a study breaking down the IQ differences in adoptive kids of white parents of different race. It goes over how methodological errors, whether motivated or not, produce racial IQ gaps as an artifact. They then re-analyse the date from such studies taking into account these errors and find much more minimal differences between racial IQ when adjusting for relevant factors.
Thomas D. (2016). Racial IQ Differences among Transracial Adoptees: Fact or Artifact?. Journal of Intelligence, 5(1), 1. doi.org/10.3390/jintelligence5010001
And in fact I'll even give you a 2022 critique breaking down the methological failings and racist motivation behind detractors of the current evidence base. Quote "[The critiqued study] serves as an example of how racially motivated and poorly executed work can find its way into a mainstream scientific journal, underscoring the importance of robust peer review and rigorous editorial judgment in the open-science era."
Giangrande, E. J., & Turkheimer, E. (2022). Race, Ethnicity, and the Scarr-Rowe Hypothesis: A Cautionary Example of Fringe Science Entering the Mainstream. Perspectives on Psychological Science, 17(3), 696-710. doi.org/10.1177/17456916211017498
Finally, there is even strong evidence that there is more genetic variability within given racial groups that between them, further legitimising the theory that differences are because of the social effects of society categorising people based on their skin colour than the genes for skin colour and intelligence correlating.
Witherspoon, D. J., Wooding, S., Rogers, A. R., Marchani, E. E., Watkins, W. S., Batzer, M. A., & Jorde, L. B. (2007). Genetic similarities within and between human populations. Genetics, 176(1), 351-359. doi.org/10.1534/genetics.106.067355
Although I disagree about a difference between sex and gender, I really enjoyed learning and asking cool questions :)
You did not need that disclaimer. That look gives all your views and opinions on this away.
good! trans supporting queen
@@luke0saur If you watched the video, you'd see it was 100% science based. The physical chromosomes, not gender expression
@@reddhoodie Explain to me what the supposed science is in >2 genders (i.e. differentiating gender from fashion and style and at the same time differentiating and between gender and sex). Just because you say it is peer-reviewed does not suggest scientific rigor. Show me the papers and explain the science. If you know anything about scientific publishing, you'd know how low the bar is for peer review and publication in some fields.
Even anti vax (Autism and MMR link paper) paper was peer-reviewed and published in Lancet.
@@SlazeM7 at no point did I say anything was peer reviewed. I said the video was only talking about the two sexes made up of our chromosomes, and NOT about gender expression
You're jumping miles here kid xD
@@reddhoodie You have a memory of a goldfish and think that everyone around you does as well.
The reason I point that out is the fact that she prefaced a science video with a disclaimer that gender is variable (>2) and separate from sex. I just asked for a definition for a start.
It's like prefacing a 'scientific' video about the age of the earth being >6000-year-old by starting with a disclaimer about its supposed different shapes.
Great video!