Why Did Two Sexes Evolve?
Vložit
- čas přidán 12. 09. 2024
- Have you ever wondered why there are two sexes? As in, why do we require sexes for sex? The origin of the sexes is actually a very interesting question in theoretical biology, and in today's video I'll be covering my favourite hypothesis for the evolution of the sexes: The Hurst-Hamilton Hypothesis.
The video is structured to cover:
- A simplistic hypothesis for the evolution of the sexes
- The hypothesis I believe to explain the origin of the sexes
- Addressing two of its main criticisms
Alongside answering the question as to why there are male and females, this video is also part of a wider evolution themed collaboration - you can enjoy the whole playlist here!
bit.ly/Evolutio...
Also, my apologies for each time I say "theory" instead of "hypothesis" - a rookie error!
Special thanks to Asher Leeks and Alan Grafen for resolving some key doubts in this video.
Inés Dawson is a PhD student and animal flight scientist at the University of Oxford.
-----Acknowledgements and other links: -----
Art & Design
➢ Channel Art & Character Design: Caro Waro / waroartwork
➢ Intro & Outro Animation: Cristina de Manuel / cristinademanuelink
Audio
➢ Soundtrack: CryoSleepKitten / cryosleepkitten
➢ Intro & Outro: Thastor / thastorcyclone
Subscribe for regular fun science!
➢ bit.ly/DrawCuri...
Check out the website behind this channel!
➢ drawcuriosity.com
Follow me on social media:
➢ / ineslauradawson
➢ / drawcuriosity
➢ / squeakcode
➢ Snapchat: squeakcode
Business e-mail:
➢ Visit CZcams about page and fill in captcha.
THE GEAR I HAVE USED:
➢ Camera
Canon 650D (US): amzn.to/2d3Wk05
Canon 700D (UK): amzn.to/2cRihfe
➢ Lenses
Canon 50mm F1.8 (UK): amzn.to/2cojvBw
Opteka 0.2x Fish-eye + Macro attachment (US): amzn.to/2cohS6X
---
Canon 50mm F1.8 (UK): amzn.to/2cRi77Q
Opteka 0.2x Fish-eye + Macro attachment (UK): amzn.to/2djiMBF
➢ Microphone
SmartLav+ (US): amzn.to/2ctsQq8
Tascam DR-40 External Recorder: amzn.to/2cPYTB0
--
SmartLav+ (UK): amzn.to/2djivyy
Tascam DR-40 External Recorder: amzn.to/2cRir6y
As always, feel free to ask any questions on this topic - as I know it's a little more convoluted than usual. :) Also, please pretend I said *hypothesis* each time I said _theory_ (rookie error... I know!).
And last but not least - don't forget to check out the playlist on how and why things evolve - from homosexuality, to facial expressions, to selfies, to words and more!
czcams.com/play/PLdNfe9CByWuYqRT3XqNZAfLsMiPwS8hRy.html
Do these hypotheses explain why in sexual reproduction there are so many species where the females are choosiest when it comes to mating preferences?
P.S. Convoluted is good. It challenges us to think more carefully.
I'd say it does by extension of the final step of the process, where you get anisogamy - you've got some gametes that are very small, which means they are cheap and easy to produce, so they've got strength in numbers - a bit like those plants that produce many seeds where only a handful will germinate.
On the other hand, perhaps for every hundred million male gametes, you have one available female gamete who has invested a lot of energy into a large cytoplasm - so it would pay for that ovum to fuse with the best possible sperm (the one carrying the better genes) to increase the fitness of her young - which is why she is choosier.
Draw Curiosity Thanks for your prompt reply. I just _knew_ that I was having a hard time getting a date for that Oscar party on Sunday because I produce too many sex cells! That _has_ to be the answer. LOL.
Short answer: Male minimal investment in child = 10 minutes. Female minimal investment in child = 9 months.
Econael: The average human male produces 1000 sperm every second. The average ejaculation is enough to make every woman in the UK pregnant twice over.
Great job making a somewhat technical topic accessible and interesting! I only just found your channel thanks to the collaboration and you definitely deserve a wider audience - subscribing now!
You're really an amazing creator! So glad I found this channel :)
Cheers! :) I feel the same about your channel!
mere speculation if God's not involved nor is it observable, repeatable, or demonstratable so be default it's not science cause it's not something we know (faith).
male and female created he them; and blessed them, and called their name Adam, in the day when they were created.
Genesis 5:2 KJV
There is no creator here, this video came out by chance through millions and millions of algorithmic interactions until we had this masterpiece in this order.
I hadn't even considered the organelle thing. That's my novel information of the day.
Fascinating stuff! You're a great speaker :)
Thank you! :)
& pretty 😍
Wow! This was super interesting! I'm curious as to what the other hypotheses are. Maybe a topic for a future video? Or short series?
Thank you very much! I thought you'd enjoy this one :)
I think I will make a follow-up video, probably a list video quickly outlining the premises of each hypothesis and potential pros and cons, as I do personally believe this theory is the one that likely explains the origin of the sexes and don't want to detract from it :)
Draw Curiosity You have a way of making difficult, even obscure, topics interesting, so when you deep dive into a topic like this, I get sucked right in. I know I'm going to end up reading more about the other hypotheses, and most of what I read is going to go over my head, so a follow-up video would do wonders to clear up what I don't understand. :D
No pressure, though. I know you have other topics you want to discuss, and I'm looking forward to those just as much. :)
I only discovered you recently, but I love your videos! You do a great job of covering more advanced/interesting topics within science that I rarely see done elsewhere. Please keep it up, I love learning new stuff!
Thank you very much for such a lovely comment! I do my best to cover interesting areas of science that I don't think get enough love - so I'm glad it's appreciated :)
(and I apologise for the multiple use of theories instead of hypotheses, cannot believe that came out of my mouth so many times! xD)
You are the best! Your videos are greatly appreciated.
I'd been wondering about this exact topic recently, although I think I'll have to rewatch this one again to fully grasp these concepts. :D And great work on the graphics and animation!
Thank you very much - especially the compliment on the animations, means a lot from someone who makes animations!
Hopefully the video will make more sense a second time round - and as always feel free to ask any questions - I love deep diving into evolutionary biology topics. :)
I really liked the criticisms at the end! When you say there are species with multiple sexes in the second criticism, are you referring to species with 3 or more parents?
Thanks! :) Given it's a hypothesis I feel addressing it's potential flaws is important!
By three sexes I meant three mating types in the population (A, B and C, where they can mate with mating types different to their own (so A with B and C, B with A and C and C with A and B)) but the offspring will be the product of just two of them. :)
Ah, makes plenty more sense! As a side note: the animations were also wonderful. Great job / keep up the good work! =)
@@DrawCuriosity Shouldnt there be just two mating sexes? A third one seems obsolete or evolutionary not beneficial. I never heard of a third one since male and female is all humanity needs to survive and how mating was intended.
@ Its hard to explain. There are hermaphrodites. You should search more about it.
@@theawesomeanarchist5053 that's not a 3rd sex they still only have large or small gameits
"The exception that confirms the rule" Ahh so close, I used to have an encyclopaedia as a kid that had "The exception that *proves* the rule" as it's mantra. Happy days.
Really interesting topic and presented very well. The hats were a nice touch on the organelles lol.
The animations in this one are awesome.
I do have a follow-up question, though: Once the destroyer-suppressor-choosy trio becomes fixed, isn't it then incentivized to invest as few resources as possible into maintaining them and, if so, do we see that? Like, it seems like modern ova would have no reason to carry awesomely powerful destroyers when all it has to do is clear out the last couple organelles that a sperm needs to survive, and likewise the sperm probably wouldn't need a suppressor anymore since it could just do away with its destroyer gene altogether and just keep the choosy gene signifier to tell any prospective ova that it's not gonna blow up their organelles. Is that what we see, and if not, is there a working theory as to why not?
Thank you very much! :D
I like this question *a lot!*
Because it is a hypothesis/model, I don't know if there have been any genes found to carry out this job. However, there are some examples of genes that mitigate conflict in similar ways (for example, some paternally transmitted IGF in rats and humans make the foetus grow more in the mother's womb, and there is a maternally transmitted suppressor for it so that the mother doesn't grow a giant baby (which would be fatal to her, but yields a higher fitness to the baby and less effort into parental care on behalf of the father because the baby is born more developed) - and example of sexual conflict on a different level resolved by "very selfish" and "suppressor" genes ), so I would imagine that would be the case, but as you say, it is possible in many cases that the systems being so entrenched, the original traces of it may have been lost (but again, I'm just speculating at this point!)
Personally, I think the mechanism explains the origin of the sexes which is the question asked, but other models could explain the maintenance of the sexes better, such as those who resolve organelle conflict in alternative manners.
That being said, if they did lose those genes and system completely, cheats would arise again, so there would again be selection to re-evolve that system, so in some cases it could also actively maintain the sexes.
Oh yeah, I forgot we probably wouldn't actually have observed the genes directly, given that they're hypothetical. This is what I get for not being a biologist. In music, we can just make suppositions and then unilaterally declare them to be true, it's a much simpler system.
Haha - that's quite alright! Part of what I love about theoretical biology is I get to learn about neat theories, do a bit of maths and a bit of speculation and critical thinking alongside it. :)
Although what I did like a lot about the superorganism evolution story is that it was a hypothesis from theoretical biology that was later endorsed as true with evidence from the natural world - so hopefully some similar conclusive evidence will be found for some of these hypotheses (though there are some compelling examples which would suggest this path was likely to the origin of the sexes)
Interesting video. BTW your new hair color fits you well, looks good.
Thank you very much! :)
Loved the video and it was super interesting! One thing I would say, though, is to be more careful when you use the word "theory". That is a very loaded and misunderstood word. Scientists can try and be more careful when using terms in a scientific context to try and separate those terms casual connotations. By equating "theory" and "hypothesis", it gives more perceived credence to people who make statements like "evolution is ONLY a theory"
Keep up the great work!
Thank you very much!
And gahhh, I know - I was kicking myself whilst editing each time I said theory, though I've tried to use hypothesis in written form where possible.
I noticed that too. It was a little bothersome to have hypotheses referred to as theories.
I think you were talking about zakir Naik lol
People can just Google the definition.
Casi nunca comento videos, pero voy a hacer una excepción.
Conocí tu canal al revisar las suscripciones de Simon Clark, y la verdad que me gustaron mucho tus videos, a tal punto que no puedo parar de verlos. Están muy bien producidos, y sobretodo, las explicaciones que llevas a cabo son muy amenas. Agradezco que añadas los subtitulos en español, ya que no tengo muy buen nivel de inglés como para comprenderlo en su totalidad (me pasa con Simon Clark, por desgracia, aunque al gustarme sus videos me esfuerzo por entenderlos, como lo haría con el tuyo si no estuviesen los subtitulos jajaja).
¡Un suscriptor hispanohablante más! :) (porque supongo que a esta altura del canal deben haber muchos más).
¡Saludos!
AAAAAAAAA!
(As in, I am a biology enthusiast with a degree in biochemistry who studies biology all day, and I hadn't considered the idea that distinguishing self from non-self was a major reason behind anisogamy, so this blew my mind).
they didn't. They were made that way.
Great video as usual!!
Do we know that meiosis appeared before different sexes appeared?
Thank you very much! :)
We don't know for sure because we weren't there, but I would imagine almost certainly yes for these reasons:
1. All the models assume that the ancestral state of the gametes are isogamous and haploid, meaning they would likely fuse together to form a diploid organism. To pass from diploid to haploid, meiosis is generally the process they undergo.
2. Meiosis resolves nuclear genetic conflict by splitting the genetic material in half such that the two gametes fusing contribute exactly 50% to the zygote.
3. Species that look like they may be in intermediate states of developing mating types do have meiosis
Thank you for your quick answer!
Which species are you referring to in #3? Can you give me an example? So interesting!
I believe various species of Chlamydomonads have multiple mating types, and _Physarus polycephalum_ has multiple sexes that co-occur within the same population.
Chlamydomonads: Whatley, J. M. (1982). Ultrastructure of Plastid Inheritance: Green Algae to Angiosperms. Biol. Rev. , 57, 527-569
The case of _Physarum polycephalum_ and the Hurst-Hamilton hypothesis are detailed here: Hurst, L., & Hamilton, W. D. (1992). Cytoplasmic fusion and the nature of sexes. Proc. R. Soc. Lond. B , 247, 189-194.
Thank you!
Video about the 8 hypothesis would be interesting! :)
Interesting video, Ines. I'm partial to Nick Lane's theory propounded in his book _The Vital Question_. I don't know a name for it.
The hypothesis proceeds from an idea I'm sure you are familiar with, that eukaryotes came about when one unicellar organism captured another into permanent symbiosis, the captured cell becoming our mitochondria. The idea is that the symbiosis, while beneficial on the whole, was a sort of genetic battleground between the two not entirely compatible genomes, nuclear DNA and mitochondrial DNA.
Lane gives two arguments from this genetic battleground hypothesis. The first explains why gene-mixing of nuclear DNA was beneficial in this situation, but doesn't purport to explain why it should be sexual, rather than universally hermaphroditic or something. I'll gloss over that because I've forgotten half of it and the other half is somewhat obvious.
I'll try to at least summarize the other argument that builds on that to explain why gene-mixing is sexual and dimoprhic, though I can't do his argument justice in a few paragraphs. In the hypothesis, the genetic battleground resulted in frequent defective mitochondria. One bad mitochondrion not being fatal to a cell, defects would accumulate over the generations.
Selection at a cellular level wasn't sufficient to deal with the problem - basically, all mitochondria in a cell, weak and strong alike, were passed on when a cell reproduced, or died with it if it never reproduced. Worse, every new generation basically remixed cells' mitochondrial complements. The selective force, as it were, had too little ability distinguish fit mitochondrial DNA from unfit.
In this hypothesis, nature's better solution was to pass mitochondrial DNA thru a sort of bottleneck, which was sexual reproduction: one cell's mitochrondria were discarded entirely, so the descendant cell depended entirely on the strength of one ancestor's mitochrondrial DNA, creating a stronger selective force for healthy mitochrondria. Ultimately cells that enjoyed this strong selective force outcompeted those that didn't.
Anyways, liked your video and am subscribed.
That is indeed one of the competing models, and is one of my favourites too! :) This also reminds me I need to read Nick Lane's _Power, Sex and Suicide, Mitochondria and the meaning of life_ book I've had sitting on my shelf for ages.
To anyone scrolling through comments, this hypothesis is also one that I think could elegantly explain sex evolution and involves organelles. :)
If eukaryotes came about when one unicellular organism enveloped another, how did the first organism to do this reproduce to create another eukaryote? Wouldn't its offspring be a prokaryote?
This question's more important: Why did discrimination between sexes come to existence ?
Because people started to put rules into Society, and then Practical Gender Roles started to become more scarce as the difference of capabilities between a Man and a Woman were starting to become thinner, yet many people take this both as a positive thing but sometimes a negative thus all this stuff happened.
I honestly don't understand those people who say "You can do whatever you want!" in the context that, they think that some people are saying you can't, some people are saying that, but in a general sense...
Of course one can do whatever they want, but of course, Human Survival has been optimized to some things, none of which are by choice, but by practical and logical reasoning, if The Rock and Scarlett Johansson were in a primitive civilization, and were given two options, a rock to kill animals for food, and finding a way to cook such animal, it won't be a sexist thing to assume The Rock chooses the Rock and Scarlett Johansson to pick the cooking, because The Rock is far larger and stronger, and because Scarlett is far more delicate and has more time to think about the situation at hand because she has time to go in-depth, of course this is an example for a primitive civilization.
The only difference now is that, well, if Ronda Rousey and Mark Zuckerberg were together, it's pretty clear what the choice might be, The Rock goes to Ronda Rousey because she's physically made for the job, and Mark tries to think of a way to cook because, same all same all...
Yes, Average Females do tend to be smaller in size than the Average Male, but that doesn't mean a Larger than average female isn't larger than a small guy, she would be...
And also, choice, we have so much choice these days, we're not completely driven to absolutely do what's practically right because society and the human ecosystem already does these things for us, therefore we have more choice and capable to do more, which i see why Sexism is a bad thing, a Woman can do what a Man can, and a Man can do what a Woman can,
but Rhonda Rousey can lift more than Mark Zuckerberg, but The Rock can lift more than Scarlett Johansson.
Tl;dr
Judgement is bad if choice is available to the individual.
How did these living forms reproduce before they evolved this method? And how were they able to extend life long enough to reach this stage?
Exactly. I dont buy it. Male and female had to be produced simultaneously. Only thing that explains it is creation
The 2 sexes can't be explained by evolution, On top of all the perfect things that fit together evolution also knew how to create the perfect system of 2 sexes that have the function of being able to create life....... By unpopular opinion An intelligent being creating this system is much more plausible then evolution creating 2 sexes on its own.
+Hop The Border Productions why would an intelligent creator choose 2 sexes? Why is it so implausible that it evolved? This video covers 2 of around 10 possible ways sexes could have evolved, it's not that unlikely
Draw Curiosity evolutionism is the belief that mindless unguided objects write programming that isn't there. Altering what's already there isn't going to write programming that isn't there.
Hey Jason,
I've noticed you've suggested that intelligent design it at play across this video's comment section on several occasions. However:
1. Evolutionism isn't really a 'belief', there exists diverse evidence that evolution is the process which shapes the natural organisms that inhabit and inhabited our world. I recommend the following video by Stated Clearly if you think there isn't evidence for evolution: czcams.com/video/lIEoO5KdPvg/video.html
2. Evolution is composed of natural selection and random mutations. This "new" programming arises from random mutations. The video explains 2 perfectly plausible routes to explain the origin and differentiation of the sexes via the process of evolution.
Over time, the effects of evolution may well appear to be 'intelligent' - however, if there was an intelligent designer who could speed up the process of evolution, I imagine we'd have even more fantastic creatures roaming this planet. I also think an intelligent designer wouldn't come up with two sexes, given it halves the population you could potentially mate with, and would devise a system whereby there'd be no potential genetic conflict between the nuclear and mitochondrial DNA, which is what the evolution of two sexes is potentially overcoming
Draw Curiosity So whales have blow holes because of their environment? Lolz. So how long would humans have to stay in the water before we get blow holes? To say nature caused evolution to choose to put the blowhole on their head is impossible because evolution doesn't have a mind.
All they did was point out commonalities among mammals in the water. The problem here is that we have not seen one animal change to become something else. Out of all the species we have discovered, you would think one of them would start to change somehow. We don't even have a documented animal that evolved. Chromosomes and bones aren't proof that random change happened. It's proof there are commonalities.
Now there has been studies in the speciation department of weather causing change in animals but it's more of an natural adaptation. In Australia I believe it was, there was a study on finches. Some changes happened to the climate and region they lived and at one point all there was to eat was seeds so the big beaked finches survived because smaller beaks couldn't crush the seeds to eat them. Big beaks mated with big beaks and more big beaks came along outnumbering the smaller beaks by alot. However this isn't an animal changing its body to match it's surroundings. Evolution doesn't choose anything.
What about species that produce asexually? What cause spontaneous creation and where does the male genetic material come from?
I'm not sure I understood the latter part of the question - but hopefully this carries some answers!
Different organisms reproduce asexually in different ways:
- those which don't reproduce sexually at all probably don't have mating types, so they are likely unicellular and would reproduce through mitosis. Some bacteria may exchange genes through a process called conjugation, which allows them to get some genetic variation, but it isn't sexual reproduction.
- some species of plants and even some animals can reproduce through parthenogenesis (or self-pollination / gynogenesis in plants) - often they are capable of mixed mating (mating both sexually and asexually depending on the circumstances), and as such they can allow their gametes to fuse with those produced by themselves.
In the cases of plants, many plants are monoecious which means they produce both male gametes (pollen) and female gametes (ovaries in the gynoecium), so they can fuse together. In animals, parthenogenesis is usually the fusion of the gametes produced by the mother during meiosis (the exact process depends on the animal) - with the caveat that the offspring are generally clonal (so no males are generated).
Haplodiploids are the exception here, whereby fertilised eggs produce females, and unfertilised gametes produce males.
Thank you for your response. It's a wonder that life happens at all considering how many things have to go right and how many things can go wrong.
Is it possible the fungi with 3 mating types had 2 earlier and evolved a third, rather than the other way around? Love the channel, biology is one of my favorite things and you do a great job of explaining it intuitively.
Bacteria just like all organisms never transition
Fantastic video!! Both content and production of amazingly high quality. Thanks! I would definitely be interested by a follow-on video to further address the two points raised at the end.
Wow, this was a heavy video but you did not miss a beat! Amazing job presenting an extremely complex topic in an easy to follow video :D
Thank you very much! :)
I watched you on Crespo's live stream, and I loved all your interventions. You got a new subscriber to your channel :)
I think I had a lecturer tell me that the male sex chromosome is fading over time as it is weaker and then there are species that had 2 sexes then went back to one. You should do a video on polyploid animals.
Y chromosome degradation is something on my list of topics to cover :D (I'd be curious to hear which species had two and then went back to one - are you referring to parthenogenetic organisms such as lizards where males have died out? although in these cases the reproduction is technically not sexual so not exactly the same), and polyploidy will be an interest topic to cover too - but need to research the literature a bit first. :) Thanks for the comment and the suggestion! :)
i just don't understand how two things can create another without design. or how an eye could come into being? you just needed to see so badly it eventually happened? or how a flower is pretty, and it smells good, purely without a designer?
If you can't imagine how it happens, then I'm sorry but you're just uneducated and dont understand a smidge of evolutionary theory.
I'm no professional, but I'll give a brief explaination for some of the things you said.
For the evolution of the eye (you can look it up for a better explaination), we didnt start with a whole eyeball magically. It happens in stages. First there is just a patch of photo-receptive cells to detect where light is and isnt. Cool, now you can tell if there is a shadow above you or not. This is useful coz u can now tell if something is above you. Next, the photo-receptive cells start to form a pit. Oooh, fancy, now you can tell which direction the shadow is coming from. Next, these photo-receptor cells form a larger pit, like a ball, as well as a lens to be able to focus light to the ball of photo-receptors. Next that lens gets muscles, which allows you to move the lens to focus your gaze somewhere. Next, the photoreceptor cells specialize into cones and rods, allowing some cells to be better at seeing blue, green or red light. Awesome now you can see colour. And so on and so forth.
As for flowers, its very easy. The flowers that are slightly more colourful and smell slightly sweeter will attract more pollenators like bees. Allowing them to make more babies. And hence the ones who are prettier, more colourful, and smell nicer will make more and more offspring while those that arent make less. Its quite simple really.
We do not need a designer to explain all of these things
Now my brain is all worked up about how the HHhypothesis will extend to the sexual reproduction of *robots*. Seriously!
Now mine is too! :p
If they go by the 'survival of the ones best suited to the environment' aka evolution, then I could see version of sexual reproduction being used. Perhaps a blending of their AI's in the offspring then some rapid selection of traits to produce a viable being.
does your significant other ever accuse u of overexplaining things? ( I joke, I jest).
I had one but one day when I was explaining something she disappeared.....
I see you took the time to render
The differences 'tween sex and gender,
But know of sexes there are two
And genders, well, you're asking who?
Sexes are by nature fixed
By the cells whose genes are mixed,
But gender is defined by us
For most two, but others plus.
I used "who" instead of "whom". Bite me.
This is amazing! :)
Thank you!
Saw this whilst absent-mindedly scrolling down the comments, should totally be higher up ^.^
@Sandcastle • There are plenty of things that don't exist that society acts out. Ideals, gods, kings, mythologies, pre-scientific theories. most ideas. ect. - most come from nature, but have since moved from genes to memes. We wouldn't want to commit the genetic fallacy.
Gender being based on sex is probably true, but that doesn't mean that this form of thinking can't lead to some absurd conclusions, like blue being a boy colour and pink being a girl colour. So The line between the objective and the subjective should rather be determined by science, then "roles" based on politics or society.
There is a destinction to be made on 'whats possible' when it comes to organization of individuals who are aware of their roles. As awareness of a role also gives one the power to reject it. Its only those who live the role without question that actually accept it.
Pandors box has already been opened in that regard, ever since we found out about evolution.. We have known ouer roles, and ouer ability to reject it is as clear as ouer ability to reject life if we so wish, despite of ouer genetic dispositions.
Really clear explanation of a complex topic. Great stuff!
Llevaba tiempo buscando un canal de ciencia sobre la biologia, hoy en dia esta de moda el universo y todas esas cosillas y no encontraba un canal sobre la biologia en español. Si es verdad que hablas en inglés pero los subtítulos ayudan mucho!! Solo conocía la primera hipótesis sobre el origen de los sexos, muy entretenido el video!!
Pdta: te conocí ayer por el directo en Quantum fracture
Muchas gracias, y bienvenido al canal! :)
Thanks to your incredible talent to make clear such complex subjects in a few words and illustrations !
wow a disclaimer for defining sex... sad. We live in sad times.
The "How Monogamy Lead To the Evolution of Superorganisms" reeled in some very interesting comments from people who abscribed and extrapolated the meaning of monogamy xD So inb4 them, I placed a disclaimer that this is purely a video about theoretical biology
good on you, don't ever let politics affect education, science and overall fun.
We live in times where non-heteronormative people are being recognized as existing and not being insane. Sure, it leads to some minor annoyances for heteronormative people describing things (at least for now); I think it's worth it.
Are you sure they're being recognized as not being insane? ( ͡° ͜ʖ ͡°) #CalmYourTits
Luis Daniel Mesa Velasquez Not by nearly enough people. : (
Much much better with the hands on thi one and awesome video as always!
Gracias! ;)
Another great video. Thanks.
thank you for simplifying such a complicated topic!
Excellent quick hurst hamilton hypothesis explainer!
Can you elaborate a little on the concept of genetic conflict with respect to having both gamete's sets of ogranelles? I think I (maybe mis)heard somewhere that more diverse organelles might create a higher probability of a harmful mutation which would interrupt cell function. Is that a coherent idea, and if so is this the genetic conflict you're referring to or is that something else?
Excellent video btw.
Very interesting! I was not aware of this hypothesis, but it absolutely makes sense. Thanks!
The Evolution of Sex has some powerful advantages that were omitted.
1. First, and foremost, sexual reproduction introduces extremely rapid variation in the sexual species by permitting recombination of diverse genomes.
2. Diploidy permits hybrid vigor in which two alleles for genes permit greater metabolic power since each may perform services that the other cannot.
This is true, but the video isn't about why sexual reproduction evolved in the first place, but rather about why sexually reproducing organisms all converge on two sexes (as opposed to gametes that can fuse with all, or more sex types) with very limited exceptions
@@DrawCuriosity To belabor the obvious, to secure the advantages of multiple genomes, clearly more than one gamete is required. Two is the smallest integer above one. Nature usually takes the simplest pathway when several are available, and so two is simpler than one. Multiple mating types still involve two gametes meeting, and probably evolved from a binary system.
TWO disclaimers?! Damn the world really is messed up these days. NONE should suffice.
My first question would be, 'Do we observe these linked organelle destroyer and suppressor genes?" followed by, "Do other hypotheses explain their existence?"
Vids like these help relieve me of the headache I acquire after reading comments on science videoes.
For some reason the audio's kinda weird, like it's loud... but I also can't hear you well.
The T.C. the audio levels work fine on my pc and phone, so it may be your device's speaker (is it blocked?). apologies for an obvious suggestion but headphones/turn sound down/turning captions on could help improve audio playback
I would think one point of critique is that the hypothesis is quite selectionist. The evolution of two sexes could simply be cause of Sewall Wrigth effect, as most traits in evolution.
Whilst I agree the hypothesis has some flaws in explaining the maintenance of sex in some species, I actually think it unlikely to be due to the Sewall Wright effect, due to the fact that systems with multiple sexes often collapse down to a system of two, and if it were a case of genetic drift, I don't think we would see two sexes to be as widespread as they are. :)
Hello, I am now reading Red Queen by Matt Ridley so I have found this video extremely interesting. Could you provide sources to find definitions of the theories you have spoken of (The Hurst-Hamilton theory and the others)? Nice hedging btw :)
brilliant and precise presentation
Thank you for this video I've been trying to understand this for a long time
"Very rarely more" than two sexes? Name one.
Some are mentioned in the video - various species of fungi have more than 2 sexes.
Very interesting and insightful. You've earned a subscriber :)
Any chance you'll make a video talking about the evolution of sex in terms of male vs female? As in, how did animals go from hermaphrodites to temperature-based sex (like sea turtles) to sex chromosomes. My one professor works with white crowned sparrows, which have a mutated chromosome in about half the population that leads to increased aggression, and almost all white crowned sparrows he looks at have one individual with regular chromosomes and one with a mutated aggressive chromosome. He hypothesizes that this is how sex chromosomes first evolved, but I'd be interested to know if there are other hypotheses related to the subject.
I'd love to make a series of videos on sexual selection and sex determination systems.
BTW - is your professor Rusty Gonser? I won't lie, I would love to talk to him about his research with Elaina!
I'm not the savviest in this area, but from what I've inferred from the research I imagine a four-sex-chromosome mating system would be quite unstable, so it would probably eventually return to being two given sufficient evolutionary time - but it's a very remarkable case of evolution in action :D
Hey, sorry for the long response time. My professor was Brent Horton, he works mainly on understanding how the mutation has affected the hormonal systems of the sparrows and using that to better understand how hormonal differences lead to behavioral differences.
There is still some mating between two aggressive individuals, which can result in individuals with two copies of the mutation. He showed our class a video of one of these individuals, it was VERY aggressive. But since these individuals can still occur, he thinks that they won't evolve to have 4 sex chromosomes since the mutation can still recombinate and so won't become reduced like the Y chromosome.
Nicely put together. What happened that different sexual organs evolved simultaneously with this theory about the gamete's evolving?
I feel u could have gotten to the answer (of the question within the title) with less word salad.
What I find difficult to understand is how does a suppressor gene evolve when having a suppressor gene is detrimental to the organelle that possesses it. Said differently, how does it help that specific organelle to pass down its own genes? Because it sounds to me that the reason implied in the video is that it helps the population overall, but I know that you know that evolution doesn't work like that (like how you explained in the inclusive fitness video) so I either misunderstood something or there's more to the story that wasn't explained.
Saludos Inés!
In this specific case, with no suppressor gene the fitness is lowest overall because the zygote is of very low fitness or even unviable if it has no organelles at all. Therefore, a suppressor gene grants a huge fitness advantage to the zygote as the whole, and the nuclear DNA (the suppressor gene is linked to the nucleus, so it would be a huge benefit for that nuclear DNA surrounding the suppressor gene). It would be worse for the organelle, but in this case the nucleus is effectively "stepping in" to resolve the conflict between them.
You get a balance between the two in the population because the situation of heterozygote advantage means that having both in an individual is the ideal scenario.
Draw Curiosity oh I think it makes a lot more sense now that I understood that the suppressor gene is inside the nucleus and not the organelle. Thank you! But I don't think that was very clear in the video (just a bit of constructive criticism ;D)
You shouldn't ask difficult questions.
You could even have stopped at "how does a suppressor gene evolve".
But everything is simple for evolutionists.
I'm confused, if organelles containing suppressor genes get destroyed, how are those genes passed on to create more gametes containing suppressor genes in the future?
+ellen the suppressor and chooser genes are found linked in the nuclear DNA, only the organelle destroyer gene is in the organelle DNA :) I probably should've made that clearer!
Ah thanks! I understand now :)
Youre my new favorite youtube scientist
The big seed and small seed idea you mentioned makes me think of R- and K-selection. How some species will have fewer kids but invest way more resources into them, whereas others like clown fish (finding nemo?) will have many but not invest as many resources into their development
Conjecture yes!! :) I was going to use those terms but then thought perhaps not many people would be familiar with them ^-^ indeed, it's a trade off of quite literally, quality vs. quantity :)
Haha yeah, I was thinking it was probably the exact same thing. The age-old quantity vs. quality debate.
Where do you think Tetrahymena and their seven sexes falls then? Does it seem more like an exception that proves the role or a transitional state?
Interesting. I'm a little confused. I'll have to watch this video a few more times to resolve it. Is that the plan? To make your videos so complicated that people have to watch them several times?
Oh no, this is a sign I haven't done my job properly (although it is one complex theory, so actually I will be very pleased if people do follow it) - although I guess CZcams will love me more if people come back to rewatch my stuff.
However, a quick summary:
Step 1: Organelle-linked organelle destroyer gene evolves to get rid of the competition. This quickly becomes fixed so all organelles carry this gene.
Step 2: A suppressor gene arises in the nuclear genome, to stop some organelles from slaughtering the other, and surrender instead. Raises fitness of zygote, and thus spreads, and leads to heterozygote advantage (mating one with and without a suppressor gene is the best case scenario).
Step 3: A choosy gene appears in the nuclear genome to ensure fusion only occurs if they are of opposite types.
Step 4: Both genes become physically linked in the nuclear genome so they are always selected together and thus forcing the two mating types.
(and eventually, you get smaller gametes that don't contribute any organelles, and larger ones that do, leading to anisogamy and what we call "sexes" from a gametic perspective). :p
Don't sweat. 2 weeks ago i had part of my brain removed. i'm still recovering. i'm definitely not the standard by which you should judge yourself.
I do get the gist of it. I guess the standard by which i judge if i understand something is could i explain it to a third party. And i could not. I'll just watch *Cake or Biscuit*...
Wishing you a speedy recovery as that is some very hardcore surgery - definitely take it easy!
Watching cake or biscuit is recommended - perhaps even moreso enjoying cake *and* biscuits!
Draw Curiosity it is some hardcore surgery. but it is also an excuse for not for not entirely following your excellent video. I'm inexplicably fine.
can I ask what exactly you were searching for when you found the footage at the beginning?
I unsuccessfully tried searching courtship in pixabay.com, currently my go-to royalty free footage site - and then just went with "animals". Except for the beetles - that I shot in Oxford last year and have been waiting for the right video to feature it. :p
Congratulations on the presentation, I found it neat!
male and female created he them; and blessed them, and called their name Adam, in the day when they were created.
Genesis 5:2 KJV
Wonderfully explained, thank you!
Is the choosy gene female or male? Is the supressor gene female or male?
Supressor gene is inside male. I just watched the video again. 🤭
so...is posible that in other palnet the dominant species have more that two sexs
03:21 sex[...] as a means to resolve conflict
Bonobos: yeah!!!
I liked that definition of sex
The comments were predictable.
Towards the end you seemed as if to dodge the question so as not to answer it directly regarding the origin of the sexes. Either that, to which I give you credit, or you are completely lost, like many others.
Amazing explanation, thank you
if this video was made today, it would be banned for being a hate crime.
No it would not. As is clearly evidenced by the fact that the video is still up. As someone who believes that gender is a spectrum, I really enjoyed this video. Sex and gender are different things.
Ay! :( Por suerte estoy llevando un curso de inglés y logro entender un poco. Veo puros comentarios en inglés que bonito.
Por cierto, soy nuevo sub, me gustan tu contenido, te vi en el directo de ayer. Un saludo desde Perú, espero que te unas más a los directos que harán CdeCiencia, QuantumFracture y otros...
+1xjhonx9 Hola y bienvenido al canal! :)
Mis videos están subtitulados al español e inglés si ayuda a seguirlo mejor :)
I don't see how the suppressor gene has a heterozygous advantage, if anything the homozygous zygote for the suppressor gene would have the advantage of having the most genetic diversity of organelles, just like how it was before the destroyer gene evolved. So what exactly is the cost of suppression that was incurred?
And another question is why would the gamete "care" to evolve a destroyer gene in the first place anyway when the organelles are not part of the cells dna? It seems more like something the organelles would evolve themselves.
Some good questions here :)
It is the organelles that evolve the destroyer genes, not the nuclear genes, because they are more likely to spread their organelle genes in future generations if they are not diluted amongst other organelles.
I made a video on Inclusive fitness here which is somewhat related to this in concept: czcams.com/video/QCrU94U997s/video.html
It is the nuclear genes that evolve the suppressor and choosy genes to overcome the resulting low cellular fitness of having few organelles - there is a conflict of interest between the two genetic sets.
The cost of suppression would incur any energy spent on translating the suppressor gene's DNA, transcribing to RNA and allocating relevant resources to the proteins for suppression (transport to membrane, creation of other proteins that interact with the destroyer gene etc.).
Therefore the fusion of two suppressor types means the fusion incurs the cost twice, whereas the heterozygous could reallocate half of those resources to other cellular processes that could elevate its fitness further.
It is a small cost compared to not having the suppressors, but the heterozygote still has the advantage, and even seemingly small advantages can be selected for by evolution, so it isn't implausible to expect selection or a system that ensures that heterozygote pairs are always formed. I guess the choosy gene would have to have a lower cost than the suppressor for this to be upheld.
Granted, this is all theoretical biology - but as a theory it makes sense. There are similar molecular systems that have evolved and are maintained in animals that mirror the one proposed here.
So, would the organelle-destroying gene be adaptive on its own (ie., does destroying the other gamete's organelles have any advantages?), or is it something like a "gene drive", where once it occurs, and because of what it does, it spreads very quickly through the population?
My gosh you meet some very cool and Interesting people on CZcams.
Cool video. Could you do one on the fungi (and other unusual organisms) that have more than two mating types?
Thanks!
I'll probably do one on sex determination systems and unusual systems :) so I'll pencil that in!
And then there is the New Mexico whiptail...
Makes me wonder how people figured such complex processes out.
you have the most amazing voice
I may not quite understand what you're talking about. But that being said you definitely do have a very relaxing voice. And as a added bonus it's extremely cute. Boom there you go!
Tienes algun video de la actual clasificacion de la vida? Has hablado de la inexistencia de la pared que separa plantas y animales? Pasa link si lo tienes 😊🙏
I'm not very informed in biological stuff but is this the reason everyone starts with the female chromosome before the male one?
Are the evolution of two sexes across widely-different organisms the result of divergent or convergent evolution?
Could you do a video on that? The answers I've tried to look up myself are... confusing
I don't know if science has an answer for this, but my guess would likely be convergent, but likely from a low number of ancestrally isogamous species.
Thank you! I was wondering if research tracing genes that regulate sexes across many species would show a common origin or many different origins (with perhaps distant species having widely-different genetic means of determining sex)
There's a lot of variation in how sex is determined (not all is genetic, some are determined based on temperature, and there is evidence for divergence there), but the majority converge on having only 2 options / "morphs" if you will. It's an interesting question, I don't know if I'll be able to find an answer but I'll add it to my list of ideas and things to look into
OK, thank you very much
"Are the evolution of two sexes across widely-different organisms the result of divergent or convergent evolution?"
I can't believe this isn't out there. (I have no interest in studying anything because I hate all mankind.)
The experts/studiers [who one should always be skeptical of, on principle] must lean toward sexual reproduction [gene/chemical exchange hermaphrodism and dimorphic sexuality [specialization]] being example of 'convergence' ('parallelism'). ...It is known that eyes have developed multiple times independently.
Dimorphic Sexuality [gender specialization] DID develop multiple times independently in animals. Arthropods and vertebrates come from hermaphrodites that became `gendered after species/line/clade divergence.
The experts must have observed further that...
~"Pond scum" (micro orgs existing in vestigial niches) show asexual reproduction in some species, sexual exchange in others AND even dim sex specialization in still others. BUT the later animals and plants (both starting hermaphro and then dim sex) don't necessarily come from the sexual or dim sex "pond scum". (For example I think the earliest animals -- 'proto placozoans' -- are Asexual.)
Also the fungi that have many multiple specialists don't just come from multi specialist 'pond scum', demonstrating that reproductive strategies (e.g sex exchange and multi morph/shape specializations) keep happening independently.
Also sexual clades (e.g animals) have members that have reverted to 'self reproduction' (they go fuck themselves) BUT they are not directly asexual orgs.
I.e there is fluidity and convergence all over when looking at repro strategies.
...
I believe the dearth of succinct info about reproductive evolution hails from the Puritans /English Civil War period (and humans generally) relegating/ shunning sex; and also from sex being "one taboo too many" when taken with 'Darwinism'. It is /was deemed taboo to focus on sex etc. (One can see what happened to an understanding of sexual ethology/behavior: strongly politically biased to absurd notions accepted without challenge [e.g "fem lions 'choose' manes"].)
Fungi seem to be a lot better off with > 3 sexes, nontheless : as explained in this article ( botit.botany.wisc.edu/toms_fungi/feb2000.html ), Fungi being dykariotic ( two nuclei ) for most of their existence makes it so that they produce sets of gametes for each nucleus, and having more sexes maximises outbreeding by making less of the spores' siblings compatible than spores in the general population ! I would like to know anyway how organite conflict is resolved, because plasmogamy does happen in the first stages of developpement and requires organites to conflict.
Really interesting video anyway, and thanks for the disclaimer at the start btw !
Thanks for the article - very interesting read!
I'm no fungi expert an expert, but my understanding is fungi avoid cytoplasmic conflict by separating the process of nuclei migration and cytoplasmic fusion when forming the syncitium.
"Therefore the model also explains the presence of multiple mating types in mushrooms and ciliates as a result of the fact that these organisms do not undergo cytoplasmic fusion during mating but rather have reciprocal nuclear exchange. "
from www.umich.edu/~mycology/resources/Research/james.FBR.2015.pdf James 2015
i love your videos Inés! :3
Did you see this article? www.nature.com/news/the-sparrow-with-four-sexes-1.21018
It's about a species of sparrow which seems to be going through an evolution towards a system with four sexes. I haven't nearly enough knowledge to start drawing any conclusions from it beyond the ones presented in the article, but I did find it fascinating.
lowercaserho I had not, thanks for sharing! it's very interesting (though a sad story about the passing of the researcher).
I would imagine the four chromosome set up to be quite unstable, so given enough evolutionary time it would likely collapse back to a two sex system - but it's really neat they've found this! :)
It was necessary to have 2 sexes, so you can be co-creators with the Creator. That's how it works and nature works in earth reality. Not sure about the great beyond realities.
But what stops the male mitocondrea shielding themselves from the attack and persisting in the cell. The female mitocondrea manage it?
Firstly, to state this is a hypothesis (I know I said theory on some occasions in the video, but I meant hypothesis in this case!). This means the mechanisms I'm proposing are speculative, but are based on similar systems which have been accounted for under other circumstances of genetic conflict.
The attack would likely be of a nature that is harder to resist, such as disrupting the mitochondrial membrane, or perhaps tagging them such that the cell automatically disposes of them or one that is so effective that the evolution of a mutation that shields them may not have arisen yet.
The suppressor gene is based in the nucleus, and likely blocks the organelle's organelle-destroyer gene (either through RNAi or by silencing that part of their genome) before fusion even occurs, meaning that after fusion it will be rapidly destroyed.
However, a good evolutionary arms race would likely involve various events like the one you describe, but given that both organelles surviving after fusion would lead to genetic conflict, it is expected that new genes in the nucleus would arise that would suppress the actions of these counter-genes such that the conflict is resolved again.
Great lesson! Now I realized that both gender were evolved at the same time from the very past. Just like Adam and Eve from the Bible. Men and women, my friend, are equally amazing.
Which animals have more than two sexes?
Would it be fair to refer "The evolution of sexual reproduction" as "Evolutionary sexual divergence"? - thanks
What do you think about Richard Dawkins's hypothesis, which involves the progressive differentiation of two types of individuals, one who spends more time in rearing offspring, and one who spends more time in fighting rivals?
I wonder if a pile of car parts where put in front of a human with no proir intelligence about car building. What would be the chance that they put all the parts in randomly but correctly? Wonder if protiens can just be randomly put together by luck or would it make more sense that a intelligent designer put them in correct working order?
Shipwreck Hubbard Hey there! I don't think that's the right question to ask to approach this problem. There is no evidence to suggest the existence of an intelligent designer, and the organisms we have today aren't the product of randomness serendipitously building a complex organism out of parts, but the gradual optimization over millions of years through evolution. It took a very, very long time for added levels of complexity such as eucaryotes and multicellular life to arise. However, when you slowly build a foundation, such as repeated genes, it provides the chance for some of the copies to mutate and develop new functions. I wouldn't say this video expands on the nuances of your question, but you might be interested in reading about the RNA world hypothesis (the channel Stated Clearly has an excellent video on this topic), and I can also recommend the book Endless Forms Most Beautiful, as it talks about the genes involved in development and how with time evolution has been able to innovate upon it. Cheers for the comment!
Draw Curiosity you could have just answered my question, but instead side stepped it . doesn't take much common sense to understand that the complexity of solar systems, and living organisms, coexisting suggest a obvious design not just random luck, if evolution is your preffered theory, or random creation . They would still have 2 of gained intelligence through trial and error, there is a obvious system in our bodies like our vascular system, our brain , our eyes, or even our dna , is a repeated code, how are codes made. Well humans do it by using precise variables thought out with intelligence, try making a video game with random codes, you will get nothing playable. Take the big bang for example, the only way we can re create it , is by building the most complex machine in human history, guided by the top scientist with a insane budget. They use calculations to align and collide the particles in a designed fashion. To believe that nature or random occurrences time and time again makes blind unguided choices and has just found a way to create working complex organisms with no intelligence is like saying that you think rockets can make there own parts and can put themselves together. Even if you don't believe in a "creator being", even nature or random creation would have gained intelligence or we would not see working system repeated and upgraded, evolution would evolve backwards because it would have no information to use. We are in a simulation of sorts and coding is in everything. Its the seed of life.
No evidence to suggest the existence of an intelligent designer? Where did the matter come from? How can something come from nothing?
I'll need a longer version to understand this because I don't really know much about the posts she's describing.
Great video! Entertaining and digestible. Would be cool to have a video covering intersex people and how they fit in to this picture.
IS THIS WHY MITOCHONDRIAL DNA IS PASSED MATERNALLY? omg this makes so much sense
are there any other hypotheses beside hurst-hamliton one?
Yep, there are at least 5-8 others, though personally I find the HH to be the most plausible
@@DrawCuriosity could you please tell me the names, because im writing a paper on why did the sexes evolve, and i cant seem to find any other theses? google hasnt been helpful...
The theory that is correct is obviously the one that receives the most funding. However if you say the HH hypothesis is true, then I'll take your word for it. Your videos are always excellent and fun.