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The Evolution of Sex
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The Evolution of Sex |
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Uncas Member
since 2010-07-30
Posts 408 |
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).] |
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Essorant Member Elite
since 2002-08-10
Posts 4769Regina, Saskatchewan; Canada |
I think it makes sense. It is similar to crop-diversity in agriculture. quote:[http://en.wikipedia.org/wiki/Crop_diversity] |
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Bob K Member Elite
since 2007-11-03
Posts 4208 |
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? |
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Uncas Member
since 2010-07-30
Posts 408 |
It's exactly the same Ess - most plants after all reproduce sexual. quote: 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.  |
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serenity blaze Member Empyrean
since 2000-02-02
Posts 27738 |
Interesting. I just watched a movie where the main character was quite adamant (and persuasive) regarding sexual evolution. From the screenplay--Roger Dodger: quote: 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. |
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Brad Member Ascendant
since 1999-08-20
Posts 5705Jejudo, South Korea |
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. |
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Essorant Member Elite
since 2002-08-10
Posts 4769Regina, Saskatchewan; Canada |
quote: Uncas? |
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Uncas Member
since 2010-07-30
Posts 408 |
Yes? |
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Brad Member Ascendant
since 1999-08-20
Posts 5705Jejudo, South Korea |
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? |
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Uncas Member
since 2010-07-30
Posts 408 |
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: 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? . |
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Brad Member Ascendant
since 1999-08-20
Posts 5705Jejudo, South Korea |
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. |
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Angel4aKing Senior Member
since 2006-09-27
Posts 1372USA |
wow |
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Huan Yi Member Ascendant
since 2004-10-12
Posts 6688Waukegan |
. Can any species other than human beings have sex face to face? Jacob Bronowski decades ago indicated no . . . . |
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