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Passions in Poetry

The Evolution of Sex

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Uncas
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since 07-30-2010
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0 posted 07-10-2011 06:18 AM       View Profile for Uncas   Email Uncas   Edit/Delete Message      Find Poems  View IP for Uncas

Sexual reproduction is a critical component in evolution, in fact without the blending of genes and subsequent variation within species, evolution is almost impossible. For that reason alone understanding why sexual reproduction evolved is a key part in understanding evolution itself.

Here's the dilemma though, sexual reproduction doesn't seem to be more advantageous than other forms of reproduction. Take asexual reproduction for instance, asexual reproduction allows an organism to create an exact clone of itself, for any organism that has a perfect set of genes sexual reproduction, where those genes could be diluted, would seem to be a distinct disadvantage. So why did sexual reproduction evolve?

There's a theory that's gaining traction among evolutionary biologists that sexual reproduction evolved as a direct result of an evolutionary arms race with parasites.  In its simplest form the theory goes like this:

Organisms are constantly under attack from rapidly changing parasites such as bacteria, a fixed genetic makeup in that situation is a distinct disadvantage, offspring of an organism that's equally susceptible to the same bacteria as its parent is a recipe for extinction. The argument is compelling but what do you think?

.

[This message has been edited by Uncas (07-10-2011 09:41 AM).]

Essorant
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1 posted 07-10-2011 10:47 PM       View Profile for Essorant   Email Essorant   Edit/Delete Message      Find Poems   Click to visit Essorant's Home Page   View IP for Essorant

I think it makes sense.  It is similar to crop-diversity in agriculture.

quote:
Generally speaking, a species has a range of genetic variability that allows for individuals and/or populations within that species to survive should a stressor or disturbance occur. In the case of agriculture, this is a tricky business to ensure, as seeds are planted under uniform conditions. For example, monocultural agriculture potentially elicits low crop diversity (especially if the seeds were mass produced or cloned). It is possible that a single pest or disease could wipe out entire areas of a crop due to this uniformity.[15] One of the more historically known examples of harvests that suffered from low crop diversity was the Irish Potato Famine of 1845-1847.
[http://en.wikipedia.org/wiki/Crop_diversity]


Bob K
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2 posted 07-11-2011 12:40 PM       View Profile for Bob K   Email Bob K   Edit/Delete Message      Find Poems  View IP for Bob K



     It's an interesting set of questions, isn't it?

     But when we speak about sexual reproduction [i]evolving[i] we may be in danger of making some conclusions about the process that may not actually fit.  

     One such conclusion might be that more complex is better.  

     How many species are there that reproduce sexually as opposed to those that reproduce a-sexually?  If you start including bacteria, and other simple and single cell organisms, not to mention those creaturely type thingies that lie on the border between proteins and organicity, such as viruses and prions, we sexual beings may be outnumbered.  That could suggest that we are not evolutionarily at the top of the success rankings.  We may only be a temporary dead end with delusions of grandeur who have been reading our own propaganda too closely and not paying very close attention to the data.

     Another conclusion is that intellect is a pro-survival trait.  Being a very recent happening on this planet, so far as we know, we have excellent information about those animals who function from the basics contained in the reptile brain, all of which are very well tested, but not very much about how useful it is to have a cerebral cortex.  Having the cortex as we do, we spend an awful lot of time thinking about it, but the survival value of that thinking has yet to be tested.

     Are we smart enough not to rub ourselves out through our own intellect-driven follies?  

     I personally have hopes.

     It's not even clear to me that having a brain makes sex more likely, or successful reproduction even a good idea.  How would you define successful evolution now, anyway?
Uncas
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3 posted 07-11-2011 01:57 PM       View Profile for Uncas   Email Uncas   Edit/Delete Message      Find Poems  View IP for Uncas

It's exactly the same Ess - most plants after all reproduce sexual.

quote:
How would you define successful evolution now, anyway?


Anything living and all their direct ancestors.

Take yourself as an example Bob, you're from a long line of evolutionary successful antecedents, every single one of your direct ancestors was an evolutionary winner going back 3.8 billion years.

When you look at things that way it makes you wonder how some people can even entertain the thought that they're a failure - every one of us is a 3.8 trillion year old success story.

serenity blaze
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4 posted 07-11-2011 02:49 PM       View Profile for serenity blaze   Email serenity blaze   Edit/Delete Message      Find Poems  View IP for serenity blaze

Interesting.

I just watched a movie where the main character was quite adamant (and persuasive) regarding sexual evolution.


From the screenplay--Roger Dodger:

quote:
- But are men absolutely necessary? - I don't know that.
Think of the structure of the female genitalia.
Wait. Wait. Okay, got it.
What is the most sensitive part of the vagina?
-I can't believe we've gotten into this. -I think you know this, Donovan.
It's the clitoris, fiirst discovered by Renaldus Columbus in 1 559.
He thought it was India.
Oh, no! No!
The crown of the clitoris contains 8,000 nerve fiibers.
It's a far great concentration than in any part of the male body...
even our fiingertips.
It is the most effiicient, pleasure-delivery system...
ever devised by nature.
Now, ask yourself...
why didn't the clitoris end up inside the vagina...
so that intercourse would be naturally...
compellingly, constantly pleasurable for a woman?
- I know the answer. - Yes, Ms. Maynard.
Because in primitive time, women died of childbirth.
So for intercourse to be too pleasurable...
wouldn't make sense from a Darwinian standpoint.
- I'm impressed. - Absolutely right.
- What does that tell us? - Evolution is looking out for us girls?
- Exactly. - That for women...
intercourse and sexual fulfiillment were never intended to intersect.
New technology just makes it offiicial.
Future generations of women will evolve clitorises-- ''clitori, clitorati''--
''Clitorissimo.''
that are larger, longer, even more sensitive.
And a woman's ability, as well as her desire to self-stimulate...
will increase exponentially...
as intercourse is robbed of its procreative utility.
- I'm confused and frightened. - You should be.
The species is not static. We're in a constant state of flux.
Two genders has been the default setting for one reason only:
So far it's been the only way to propagate the race.


You can find the rest of it here:
http://www.script-o-rama.com/movie_scripts/r/roger-dodger-script-transcript-eisenberg.html

Of course, much of it is um, tongue-in-cheek, as for entertainment value, but I thought it was quite intriguing.
Brad
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5 posted 07-12-2011 03:01 AM       View Profile for Brad   Email Brad   Edit/Delete Message      Find Poems  View IP for Brad

A quick question:

Did sex evolve one time or several times?

A couple of examples:

The eye has evolved multiple times.

Wings have evolved, I think, four times: insects, pterosaurs, birds, and mammals.

There's also the whip-tailed lizard that reproduces through parthenogenesis.  They're all female and all clones.

Essorant
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6 posted 07-18-2011 02:13 PM       View Profile for Essorant   Email Essorant   Edit/Delete Message      Find Poems   Click to visit Essorant's Home Page   View IP for Essorant

quote:
Did sex evolve one time or several times?


Uncas?
Uncas
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7 posted 07-18-2011 02:23 PM       View Profile for Uncas   Email Uncas   Edit/Delete Message      Find Poems  View IP for Uncas


Yes?

Brad
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8 posted 07-18-2011 04:48 PM       View Profile for Brad   Email Brad   Edit/Delete Message      Find Poems  View IP for Brad

Now that was funny.  

An intriguing position that I think coincides with sex is the evolution of evolvability.  The idea is that certain morphologies are selected for, not because they have an edge in any particular niche, but because they can adapt to multiple niches faster than others.

This is where I think Uncas was going when he was talking about evolutionary dead ends.  We and many other groups are too specialized to adapt to a change in the environment.

At bottom, the process is still Darwinian, but it adds a nice twist, no?
Uncas
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9 posted 07-18-2011 06:58 PM       View Profile for Uncas   Email Uncas   Edit/Delete Message      Find Poems  View IP for Uncas

Yes isn't a bad answer actually. It's not really correct but then again it's not wrong either. It depends on the definition of sex.
  

quote:
This is where I think Uncas was going when he was talking about evolutionary dead ends.



Abso-bleeding-lutely.





When the next meteorite hits it probably won't be humans that rise from the ashes.

But not just that, in my view reproduction answers a lot of questions, for instance:

Why did simple organisms rule the earth for millions of years before higher forms appeared?
What drove the Cambrian explosion?
Why does evolution seem to jump in leaps and bounds? (Gould's punctuated equilibrium.)
Why is the belief that parasitism drove evolution correct but not in the way you might think?

.
Brad
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Posts 5896
Jejudo, South Korea


10 posted 07-18-2011 08:30 PM       View Profile for Brad   Email Brad   Edit/Delete Message      Find Poems  View IP for Brad

I don't want to hijack this thread (assuming you have a direction here -- I usually do when starting a thread but the tangents are too interesting to let go.) but you've brought up some interesting questions.

What drove the Cambrian explosion?

I know of three hypotheses here:

a. the evolution of the eye

b. Yeah, sex.

c. A combination of both.

Now, what got those going is explained by the snowball earth hypothesis. They're not talking about an ice age, but a period of time when earth's oceans almost completely froze over.

Are we a dead end?

In a way, yes.  Right now I'm kind of tied to the idea that if we can make it through the next couple of centuries, we'll split.  That is, through our own making, we'll have different genomes (Perhaps not even with a DNA base).  It seems very well possible that at some time in the future the human genome as we know it will cease to be.

This doesn't bother me.  I don't have any loyalty to my genome (it's far too homogenous anyway), I do have some loyalty to thought however and in order to preserve that it seems to me that diversity is the way to go.
Angel4aKing
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11 posted 10-14-2011 01:38 AM       View Profile for Angel4aKing   Email Angel4aKing   Edit/Delete Message      Find Poems  View IP for Angel4aKing

wow
Huan Yi
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since 10-12-2004
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12 posted 10-23-2011 08:18 PM       View Profile for Huan Yi   Email Huan Yi   Edit/Delete Message      Find Poems  View IP for Huan Yi

.


Can any species other than human beings have sex face to face?
Jacob Bronowski decades ago indicated no . . .


.
 
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