Why Two Sexes?

[Polymath257]

No. See post 52.

Wow. Great minds work in the same gutter....or something like that. I looked at your post before it was edited to include the description of the Asimov story. Good job!

"Against stupidity, the Gods Themselves contend in vain" --- LOVE that quote.

 

[exchemist]

Wow. Great minds work in the same gutter....or something like that. I looked at your post before it was edited to include the description of the Asimov story. Good job!

Hahaha. I remember enjoying that story very much when it came out, back in the 70s, the year I went up to university, I think.

(It's a lazy habit of mine to often edit my posts just after posting them: somehow it's only when one sees it on the page that one thinks of something extra to add. Sorry for any confusion.)

 

[Polymath257]

Never read the story. But now that you've mentioned trisexuality, I've gotten all hot and bothered.

As @exchemist noted, the trisexuality isn't central to the story, but it adds a nice sense of alienness.

 

[exchemist]

Wow. Great minds work in the same gutter....or something like that. I looked at your post before it was edited to include the description of the Asimov story. Good job!

"Against stupidity, the Gods Themselves contend in vain" --- LOVE that quote.

Somehow even better in Schiller's original, even though I don't speak German: Mit der Dummheit kämpfen Götter selbst vergebens. There is something about that word Dummheit......

 

[Milton Platt]

It is generally accepted within the evolutionary sciences that sexual reproduction became the dominant form of reproduction mainly because it was superior to asexual reproduction as a means of combating diseases and parasites. There's quite a bit of agreement about that.

But why did two sexes become the dominant number of sexes for a species to have? Why not three sexes, or 16 sexes (as are found in some species of insects) or 16,000 sexes (as is found in some species of fungi)? Why do almost all species have only two sexes?






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Can you support with links to articles that two sexes is superior to asexual reproduction because of it's ability to combat diseases and parasites? I am not anti-evolution....I just would like some background to support this conclusion.

 

[crossfire]

Are there species with both sexual and asexual reproduction? I was not aware

Corals are one example. Many other marine invertebrates, such as starfish also reproduce both sexually and asexually. Many types of flowering (sexual reproduction) plants also propagate asexually via division or budding. Some insects also have both sexual and asexual reproduction. Some vertebrates can reproduce via parthenogenesis or sexually. (see wiki link for parthenogenesis provided.)

 

[Polymath257]

I was thinking about the frogs too. I may be wrong here (or have the cat by the wrong tail) but don't they sort of like flip between genders? I.e. when there are too few males, a female might turn male.

Here's a recent article I just found discussing the mechanisms by which temperature controls the development of males/females in certain turtles:

How turtles use temperature to figure out their sex

Evidently, it is ultimately determined by a regulator protein that is sensitive to calcium.

Now, this is a species that does NOT flip sexes, but where sex is not determined genetically either.

I'm curious if there is a similar mechanism for sex flipping in species that do it.

 

[crossfire]

Can you support with links to articles that two sexes is superior to asexual reproduction because of it's ability to combat diseases and parasites? I am not anti-evolution....I just would like some background to support this conclusion.

Irish potato blight famine is one example where disease can quickly spread through asexually reproduced populations.

Here's a link for you:
22 Advantages And Disadvantages Of Asexual Reproduction

 

[Polymath257]

Can you support with links to articles that two sexes is superior to asexual reproduction because of it's ability to combat diseases and parasites? I am not anti-evolution....I just would like some background to support this conclusion.

It's called the Red Queen Hypothesis. Here are a few articles for your perusal.

https://www.journals.uchicago.edu/doi/abs/10.1086/599080
Running with the Red Queen: Host-Parasite Coevolution Selects for Biparental Sex
https://royalsocietypublishing.org/doi/abs/10.1098/rspb.1991.0063
The Geographic Mosaic of Sex and the Red Queen - ScienceDirect

 

[crossfire]

Here's a recent article I just found discussing the mechanisms by which temperature controls the development of males/females in certain turtles:

How turtles use temperature to figure out their sex

Evidently, it is ultimately determined by a regulator protein that is sensitive to calcium.

Now, this is a species that does NOT flip sexes, but where sex is not determined genetically either.

I'm curious if there is a similar mechanism for sex flipping in species that do it.

Clownfish will flip sexes based on dominance hierarchy, with the top of the hierarchy becoming a female. (They are born male, but mature into female.)
Amphiprioninae - Wikipedia

 

[Evangelicalhumanist]

Can only see one clearly obvious answer... If there were only men, how would the dishes and laundry ever be done?

(Now ill just sit back and wait for all the likes )

No likes from me! I'm male, and I do all the dishes and all the laundry.

On a more serious note, I think it would be smarter if we were all hermaphrodites. Think about how many issues that could solve in regards to inequality.

Wouldn't work. You'd need to be multi-coloured, as well. And then you'd have to cope with those who think being white on the left is clearly inferior to being white on the right. A lot of humans are never happy until there's somebody they can feel superior to.

 

[Evangelicalhumanist]

Never read the story. But now that you've mentioned trisexuality, I've gotten all hot and bothered.

What's a trisexual? Somebody who'll try anything, three times?

 

[Evangelicalhumanist]

Clownfish will flip sexes based on dominance hierarchy, with the top of the hierarchy becoming a female. (They are born male, but mature into female.)
Amphiprioninae - Wikipedia

You've just ruined Nemo for everybody!

 

[cataway]

a Atheist never will be able to understand

 

[Double Fine]

My *guess*, and it is purely a guess, is that they probably determined sex by environmental signals and that the XY system (and the ZW system) came later.

Unfortunately, we may never know on this issue. This doesn't preserve well in the fossil record and no good comparison species currently exist as far as I know.

I just did a quick check to verify that marsupilas and monotremes use the XY system: they do.

I think I missed this last night. I forget that I have to refresh frequently.

Yes, all we can do is guess, BUT, I do think that there is something in here about mammals being homeothermic and viviparous. I might be wrong (and if any geologists and/or palaeontologists are present to correct me, I'd be much obliged) but I am pretty sure that the synapsids were the first group of animals that traded egg laying for live birth, as well as the first group to be warm blooded. As far as I know, no other members of Kingdom Animalia were either of those things around 300 million years ago.

Obviously, we could probably have a debate as to exactly when protomammals evolved these abilities but it would seem to me that those changes made the XY chromosome system a little bit more useful for our most ancient of ancestors.

Anyway, very much off topic here, but a certainly a fun discussion to have one day.

 

[Double Fine]

Am I the only one that thinks of Asimov's story 'The Gods Themselves' when discussing the possibility of trisexuality?

Asimov is a bit before my time, sadly. What a legend he is though

 

[Polymath257]

I think I missed this last night. I forget that I have to refresh frequently.

Yes, all we can do is guess, BUT, I do think that there is something in here about mammals being homeothermic and viviparous. I might be wrong (and if any geologists and/or palaeontologists are present to correct me, I'd be much obliged) but I am pretty sure that the synapsids were the first group of animals that traded egg laying for live birth, as well as the first group to be warm blooded. As far as I know, no other members of Kingdom Animalia were either of those things around 300 million years ago.

Unlikely since the monotremes are also descended from them and the monotremes lay eggs today, even though they are mammals.

 

[Polymath257]

Asimov is a bit before my time, sadly. What a legend he is though

One of the nice things about books is that we can share the ideas of those who were before our time.