Sexes

[NavajoEverclear]

Hey its been a while since i was here. I'm working on revising my mentality to not be such a time waster. Anyhow i was wondering this just a moment ago, and a feel like asking so here i ask.

 

How could sexes have evolved (not saying that as in that i lean to it not being true, just as in a way as we were not there so all we can really say is what COULD have happened). I may guess that someone will say something about gradual mutations that had better chance of survival, became more common, then kept evolving. But that wouldn't satisfy me. PRECISELY why did there become different sexes (maybe it started with bacteria?) when did there actually become male and female? Er, i guess thats sort of the same question but I know there are bacteria that sexually reproduce, but they only call it that because there are two parents to produce offspring, neither is male or female.

 

so, how, when and why is it proposed that male/female things began, and what are some basic steps in the evolution of them to become what it is today?

[iglak]

NavajoEverclear said in post #1 :

there are bacteria that sexually reproduce, but they only call it that because there are two parents to produce offspring, neither is male or female.

i just recently heard this from my teacher:

sometimes, a sort of tunnel will form between two bacteria, allowing them to trade DNA portions. this is what causes a lot of the bacterial mutations.

 

although, i have no idea if that has anything to do with sexes....

[Skye]

Nah plasmids in bacteria have nothing to do with sexes in us, it's just a confusing use of the same terms. The thing we have to figure out is the origin of meiosis, where the chromosomes are split in two then cells unite and the corresponding chromosomes join. This probably started occuring in single celled protists. At first it would have less well organised than proper meiosis, with cell fusions and polyploidy, and occasional haploid mitosis. It became more refined and standardised, and then meiosis itself developed seperately in several groups of animals and plants.

[gene]

Without either sexes, the fusion process can not occur. A sperm without an egg is nothing and vice versa. And when we can't reproduce, the human race will become extinct.

 

Come on, think about, without both sexes living in the same world. It would be quite boring right? Then this world would become a place full of homosexuals. And diseases will start to rise. Once again wiping the whole human race. Asking why there is a boy and a girl is like reading God's mind.

 

Also, without male and female. Think about evolution. It would have some errors in its theory. Because Nature has create this wold in such a way that the male shall compete and fight for their mate. Competition would cease and life would undoubtedly be boring.

 

I think this question is not really one that can be answer by science alone. Because it reminds me of this question. Why is this universe even created. And what the heck, why are we even here. Sitting in front of the computer and all that stuff.

 

We need the opposite sex not only for sexually desire. (THat's points out one more point. What are the hormones for if there is not opposite sex?) For companionship, as a friend.. Etc. That goes to another point. Mankind's vulnerability of all these things.

 

Ok. i am talking crap now... it is getting further away from the topic. Ok, plain simple answer. I am not sure myself too.

[jordan]

This is a very good question. From an evolution standpoint, a being evolves to the betterment of itself. Your question asks how two can evolve for the betterment of both of them. I don't have any ideas on this one.

[Emmon]

theres an article in NewScientist about this topic this week, how sex is so common in living creatures. It goes onto say how a good idea would be that genes are more easily carried down the "family tree". In asexual reproduction its essentially 1 set of genes being passed on. And even a fabolous set of genes 10 thousand years ago would hardly be likely to be up to scratch today. If they are mixed however, with "survival of the fittest" occuring.. the product will be healthier young.

 

Constantly changing enviroments give sexual species an advantage.. being able to choose the partner that they think will help their young cope in X or Y environment best.

[YT2095]

if I were to hazzard a guess, based on the evidence we do have and know. I would have said it should have something to do with mutual bennefits across slightly differing organism. if we look at the scale of the nano to the macro, we`ll see that many nano organisms are Asexual and the macro ones have 2 sexes. where along this scale is there a bridge between the 2 opposites?

well lets look at Bees, the entire population is male, with the exception of one queen, so I`m guessing here that once upon a time, the bees ancestors were asexual and through some genetic fluke (a stray cosmic ray?) made a bee that was a little different and that population thrived alot better than its ordinary counterparts. and this difference was passed down to it`s young and so on. lets look at snakes now, there are male and female snakes, but under certain conditions the female can indeed self fertilise and give birth to young without the need for a male.

it is also documented that during our 9 month gestation period, there is a point where we are actualy all Female until certain hormones kick in and determine our sex.

the above it ONLY an idea/guess, NOT to be taken as fact at all, just an opinion and pointers as to where it maybe a good idea to look at.

[Skye]

With the bees the workers are all female. The only males are 'kings' which sit around and fertilise the queen occasionally. The thing is that all the females have two sets of chromosomes (diploid like us) and the males have only one (haploid like bacteria). Females are the result of normal sexual reproduction, males from an unfertilised egg. This means that a female is actually more closely related to her sisters (at least if they share the father) than her own daughters, and so she is better off looking after her sisters, her 'co-workers' in the hive, than producing daughters of her own. Worker bees are actually able to still produce males (they aren't able to mate to produce females though) but this is pretty brutally discouraged by other worker bees.

 

BUT getting back to the topic, the inbetweenees are hermaphrodites, which have both male and female organs. This includes quite a few animals, like garden snails and barnacles (choosing a partner for barnacles is limited to who's in reach), and most plants. So I think the likely predecessors to seperate sexes were sexual organisms that had both sets of gear.

[NavajoEverclear]

Well we wouldn't really be female besides as far as is structuraly detectable, because we carry our full genome in every cell of our body (right?) so every particle (cellular) of any female speciman, is strictly female, as it has no Y chromosomes, any male is definately male because it only has one X, then the Y.

 

I like your view Gene, accept that thing about us all turning into homosexuals, because that wouldn't happen. It would super severely suck if it did though. I infinately enjoy being heterosexual, girls are so freakin awesome (especially my favorite one).

 

So about that protist thing---- if thats possible there must be links in the chain, and i would think that some of those links should still exist today, because there must have been a huge amount of evolution between acomplishing the final masterpiece of a refined male/female system. So i guess what i want to know is what is the most primitive form of genetillia, because thats where the huge difference is. How did some organism begin to have two different types of itself that fit together specifically (as in the male can only mate with a female)?

That hermaphodite theory is almost plausible, but in an asexual organism, what would be the point of developing sex organs? I don't see why it would happen. I mean obviously i see that it would be beneficial, but things don't happen just because it would be great if it did. It would be hugely beneficial if we could fly, but evolution being blind, is not working us any closer to that objective. I understand mutations may accidentally work out, but such thing's as orderly as sexuality cannot be put together by sudden random mutation.

[Sayonara]

Good luck being heterosexual in an all-male environment. No really, I hope you enjoy yourSELF.

[alt_f13]

Ha.

[Skye]

"there must have been a huge amount of evolution between acomplishing the final masterpiece of a refined male/female system."

 

Even the simplest animals, sponges, can produce sperm and eggs. So while there has been change in the specific way animals go about sexual reproduction, the basic cellular process has remained much the same since the protists.

 

"So i guess what i want to know is what is the most primitive form of genetillia, because thats where the huge difference is. How did some organism begin to have two different types of itself that fit together specifically (as in the male can only mate with a female)?"

 

The first penis/vagina setup was probably in early reptiles, where it aids in internal fertilisation.

 

"That hermaphodite theory is almost plausible, but in an asexual organism, what would be the point of developing sex organs?"

 

We developed sexual reproduction before we had organs at all, as the sponges don't have organs as such, but do sexually reproduce.

[YT2095]

well back to my original post, there MUST be, somewhere along the scale of the NAno (largely asexual) to the Macro (almost always sexualy divided) that there is a "link" or a "Bridge".

Not being a biologist myself, I can`t think of what it could be (other than something I probably couldn`t even pronounce!).

my 1`st thought`s were bees (that was wrong) and then snakes, the females that can reproduce asexualy under certain circumstances. this really IS a good question!

[Sayonara]

It depends what you mean by "link"?

[YT2095]

a bit like the "Missing Link" in evolution for Man

some sort of halfway area where there`s on the scales the ballance between male/female, and asexuality.

some sort of transitional species either in records or still currently alive

[Sayonara]

But that would have to be a common ancestor species (or, more likely, family) for all sexual organisms that have ever lived.

 

I looked back to your original bees post which I missed before. It's highly unlikely that a cosmic ray (or anything causing a single mutation in 1 individual) triggered a fundamental change in the way the entire life cycle of the species works, but I get what you mean.

 

The snakes thing I'll look into but I have never heard of self-fertilisation in reptiles before.

 

As for human gender differentiation... modifying one process is easier than creating a new process to do something the body is pretty much doing already, hence the lack of elaborate mechanisms for making boy human worm-babies and girl human worm-babies.

[atinymonkey]

I assume you mean way, way, way, way back. As in hey Mr Simple Organism, whacha doin'?

[YT2095]

well I`m not sure, as I said, I`m no biologist. it just seems that we have a plethora of different creatures here, at both ends of the scale, it would seem to make sense that somewhere along it would be something in a transitional phase that we could observe and get a little more understanding from as to the question in post #1

[Sayonara]

Such an organism would have to be fairly basic, as it's difficult to have complex multicellular life that does not utilise sexual reproduction.

 

There's probably a nematode or something that fits the bill.

[YT2095]

yeah, I was figuring it would have to be something along those lines, there maybe (I don`t know) others close to it that are NEARLY sexulay divided, some completely transitional and others still begining to experiment (so to speak).

the female snake thing is fascinating tho! esp as it`s a "Macro creature" as I call it, maybe organism would be best?

there was one locked in a lab for for ages, never seen a male for contact ever, and it gave birth to 3 perfectly healthy baby snakes all on her own. this caused great interest and subsequent experiments were done, and it turns out that the female CAN self replicate without the male participation under extreme conditions

[Skye]

There's a species of lizard that's all female, the egg develops without fertilisation. They need to copulate with each other to stimulate a hormone response.

 

I'm fairly sure sex first started with protists, they are the intermediates between bacteria (which don't have sex) and plants, animals and fungi (which do), and many of them have both a sexual phase and asexual. And it's considered pretty likely sex has actually arisen a few times within them.

[YT2095]

AHA!!!! good point, you`ve just reminded me of something when you mentioned Plants.

Cannabis for example has a distinct male and female plant, however hermaphrodites can be generated under certain conditions and ALSO (and get this!) you can have ONE plant that has male branches and others Female! they`re not heraphrodites, the parent plant mabe a pure male or female, but certain techniques can stimulate hormones along a branch and they (hormones) don`t travel back along it and affect the main plant.

I`ll point out 2 things tho, it does require the pollen of the opposite sex and must be done at the correct time of year for flowering maturity. point number 2. I have NO personal experience with this whatsoever! it`s pure science only

[Skye]

Similar to genetically male people (have a Y chromosome) that are insensitive to male hormones. As their cells don't recognise male hormones they develop largely into a woman.

[YT2095]

huh?

[Skye]

What's the bit you don't get?