Why Was Sexual Reproduction Selected?

[Borodog]

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I don't understand what you're accusing me of. I plead innocent and carry on.

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I have no idea what sex has to do with the "progress" argument.

[/ QUOTE ]The (more complex) model of sexual reproduction is "used" by the more complex organisms on Earth. However, Homo Sapiens --and his relatives-- did not appear as the result of some inexorable march towards more complexity, but, rather, through sheer happenstance. I claim that progress is not inherent in Nature (which is disturbing news not just for creationists!), so, sex was "selected" ---to use your man's lingo-- in the limited area of animal life as part of topical evolution, while asexual reproduction is here, it is prevalent and will almost certainly outlast the alternative model (ours).

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It has been pointed out repeatedly that the sheer numbers of asexually reproducers do not make sexual reproduction a thing to be airily dismissed, so why do you keep trying to do it?

[/ QUOTE ]I'm trying to do something very simple yet it seemingly goes over many heads: Our model of reproduction (the "sexual" model) is exceptionally important for our species' survival. For one thing, it keeps our gene pool changing quickly enough to confuse the parasitical micro-organisms that are out to get us.

But, our model has been "selected" for a small minority that's been onstage for a few "minutes" in the "year" of Earth's lifespan. We should admire a model that's topically very appropriate and successful, but we should also understand that it's inapplicable and not "selected" by the vast majority of organisms, ever since Life began.

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Why do you keep trying to kill my man's thread?

[/ QUOTE ] Hmkpoker asks "why was the two-sex, sperm/egg congress paradigm selected". The answer is that this paradigm was "selected" topically because it was best for the area it covers. Evolution is real; natural selection is real; and progress exists --albeit in spots and spurts. Sheer randomness rules.

Hmkpoker also says "Many species have the ability to reproduce asexually, and [one] would think that that's more advantageous to survival as it's simpler." The response is, Yes, it is more advantageous, which is why it is used by the vast majority of Life and for a much longer time than the alternative.

Mickey Brausch

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This is just silly. Sexual reproduction is clearly advantageous, somehow, or else the vast majority of the plant and animal kingdoms wouldn't use it; it's incredibly costly. The fact that the majority of species (bacteria) don't utilize sexual reproduction is not an indication that sex is somehow not advantageous, it's much more likely to be simply an indication that bacteria are just not complex enough to take advantage of it.

[Rduke55]

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However, [censored] Sapiens --and his relatives-- did not appear as the result of some inexorable march towards more complexity, but, rather, through sheer happenstance.

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While it wasn't a predetermined march, our species was limited as to what kinds of forms it could take. We were built on the foundations of other complex animals and there's where the constraints come in.

Separately, while you can't predict it, sometimes traits arise in evolution that really open new niches so you get an explosion of new forms, species, etc.
Look at multicellularism, the bilateral body plan, segmented appendages, image forming vision, flight, terrestiality, and sexual reproduction (to name a few). Once these pop up, you can see that lineages with them really branch out and take off.

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" so, sex was "selected" ---to use your man's lingo-- in the limited area of animal life as part of topical evolution, while asexual reproduction is here, it is prevalent and will almost certainly outlast the alternative model (ours). "

"But, our model has been "selected" for a small minority that's been onstage for a few "minutes" in the "year" of Earth's lifespan."




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I think that this is the problem people are having with your posts in this thread. First as both Borodog and Madnak pointed out, it's not just animals that have sexual reproduction. Nearly all multicellular life has it (which makes it not just "our" model). So it's not just some sliver of life that's been around for a "few minutes" - but a major component of it. Multicellular life has been around for over a billion years, and while that's still technically in the minority of life on earth you're making it out like it's an insignificant part. Considering life's been around on earth for about 4 billion years or so, we are talking about a pretty decent chunk there.

Basically, hmk asked "what's the advantage of sexual reproduction - why do all these organisms not take part of the apparent advantages of asexual reproduction" and I think you may have misunderstood his post, looking at it from him saying just humans (or some other small subset of organisms).

[Skidoo]

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The sex drive is about as important as eating and survival, and it's so radically different than asexual reproduction that I can't imagine it not having a significant impact.

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Indeed, sexual reproduction is so different from the asexual sort that it's difficult to imagine a sequence of developmental stages in explanation of how the former could emerge from the later. Not why, but how.

[madnak]

Look, spend a billion years thinking about it and maybe you'll get somewhere. By the way, RDuke, is what I said mostly on-target?

[Skidoo]

How amusing. I meant in the same context of scientific investigation as the events themselves are proposed.

[Rduke55]

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Look, spend a billion years thinking about it and maybe you'll get somewhere. By the way, RDuke, is what I said mostly on-target?

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Ideas vary on this one. Depending on how strict you are on the definitions but you're pretty on with the "starting as a secondary mechanism" deal.

As to the generation length/ population size, I'm not quite sure what you mean here (as in which causes what for example).

[madnak]

Just that bacteria can "afford" to reproduce asexually because they reproduce so quickly and efficiently that they'll be able to respond to environmental changes relatively easily. A multicellular organism, on the other hand, needs some mechanism for diversity because of the investment.

[Skidoo]

I think it would be an excellent contribution to this thread if you could provide the name of a process, or a link to the description of a (complete) process, whereby an asexual population develops into a sexually differentiated one. Not so much why such a thing would happen (that much is easy enough to imagine), but what intermediate stages would be gone through as it happens.

[Rduke55]

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I think it would be an excellent contribution to this thread if you could provide the name of a process, or a link to the description of a (complete) process, whereby an asexual population develops into a sexually differentiated one. Not so much why such a thing would happen (that much is easy enough to imagine), but what intermediate stages would be gone through as it happens.

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Would it really make a difference to you?
Anyways, as another poster (thyalcine?) mentioned earlier, prokaryotes and protocellular life can transfer genes between each other.
Does this satisfy you?

If not, meiosis is THE process needed for sexual reproduction. Many of the same mechanisms that are involved in mitosis are used, so a lot of it is basically just adding another round to get some haploid progeny.

The yeasts S. cerevisiae and S. pombe as well as the malaria plasmodium P. falciparum are terrific examples of sexual reproduction using primitive meiotic processes. Their close relatives cannot perform this process and the genes involved have been pretty well characterized. These meiotic processes are also seen in some multicellular lineages that the fossil record and molecular clock dating support as diverging earlier. Later divergers have synaptonemal complexes which allows them a more sophisticated meiosis.

Once life had meiosis, everything was pretty much in place for sexual reproduction.

[Rduke55]

Also Skidoo, I think this discussion is not along the lines of the OP's question. For the purposes of this thread, we are assuming that these evolutionary processes took place. Imagine the OP said "Let's all start out as accepting X,Y, and Z. Given that, what advantages would blah, blah, blah have over blah, blah, blah?"
Pretend it's a game or something, otherwise every thread talking about the mechanisms and specifics of evolution will devolve into these arguments.