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Life and the Evolution of Sex

Discussion of everything related to the Theory of Evolution.

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Life and the Evolution of Sex

Postby adriaanb » Fri Oct 10, 2008 12:36 pm

Life is a replicating molecule. The evolution of life is best understood as the replicator 'sliding down the hill of replication errors'.

See the diagram below, each red dot is a replicator that is still alive today. Every mutation that manages to crowd out the original or split off makes the replicator drop downhill. Uphill we find the least-mutated life forms still alive today. Towards the bottom of the hill we find the most-mutated forms still alive today. All life forms originate from the top, from the same replicating source, and have been alive for the same amount of time.

Nothing that happens downhill can serve as an explanation for anything uphill, because faulty replication is not a process that can look ahead in any way. Downhill, replication generally becomes more energy intensive and the replicator becomes more vulnerable to external disturbances due to the specialisation on specific energy sources. This vulnerability causes most life forms to die out as they slip further downhill.

Image

Sexual reproduction.
A mutation to a replicator stumbles upon sexual reproduction. Now mutations that survive without fixating are allowed to build up among the sexually reproducing organisms. Sexual reproduction changes the single gene line into a gene pool of genetic diversity available to the replicator.

The introduction of a gene pool causes two important changes to life:

1. A replicator building its organisms from a gene pool gets an extra lease of life because it gains a resistance against external disturbances. It can adapt within the gene pool without further mutations (like the peppered moth) keeping the replicator alive for longer. The genetic diversity within the genepool acts as a buffer against external disturbances allowing the replicator code to stay alive through genetic recombination.

2. The sexually reproducing replicator becomes more vulnerable to mutations, causing increased complexity and speciation. A mutated gene can recombine in many more ways than before. This increases the chance of finding a combination that is capable of crowding out the original or splitting off, causing it to drop down the hill.

But these two effects can not be the cause of sex appearing in evolution. They occur downhill from where sexual reproduction first occurs, after the build-up of a gene pool by further mutations.

The cause of sexual reproduction is the increased energy efficiency offered by building in an error prevention and correction mechanism in the replication process, allowing the mutated replicator code to crowd out its original. Sexual reproduction prevents the replicator from wasting energy on building faulty organisms that won't make it to replication (see earlier posts). This lets the sexually replicating version achieve a higher growth rate on the available resources, crowding out the original.


Cause and effect of sexual reproduction.
This clear distinction between horizontal 'adaptation within the genepool' and vertical 'mutation downhill' can explain the cause and effects of sexual reproduction. The abundance of sexually reproducing life in today's world is due to the buffer a genepool provides against external disturbances and the increased vulnerability of the replicator to mutations that can take over or split off. Sexually reproducing life is caused by a mutation introducing an error check in replication which allowed it to crowd out the original.

Present theories on evolution lead to confusion because they clump together adaptation within the genepool and mutation 'downhill' into a general mechanism called adaptation/evolution. To understand the cause and effect of sexual reproduction, these two aspects of life need to be clearly separated, like the model of the 'hill of replication errors' does.

Adaptation happens only within the genepool (by my definition). It is a largely reversible, almost directed process. Life is bound to find the 'best' genetic combination, given enough time for genetic recombination. Adaptation is about organisms within one species outperforming each other. Adaptation can occur without changing the potentially available code to the replicator. Adaptation can be seen as the replicator moving horizontally on the hill.

Mutation downhill is a largely non-reversible, pure chance process. Due to its path dependent chaotic nature it is very hard to predict where it will go. Mutation is about permanent changes in the code available to the replicator, these are changes that affect the species in general. Mutations can open up long avenues of adaptation that life can take at great speed. This could give rise to 'sudden' large changes in a species phenotype. Mutations can be seen as the replicator slipping down the hill.

Both adaptation and mutation happen because changes in the organisms phenotype give it certain advantages over others within the same species. The difference is in whether it needs 'new code' or not.

I think the model of the 'replicator sliding down the hill of replication errors' may give more insight into the cause and effects of sexual reproduction. I would be happy with any comment.
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Re: Life and the Evolution of Sex

Postby enarees » Sun Oct 12, 2008 5:11 am

Sex is one of two important causes for evolution/creation.
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Postby mcar » Wed Oct 15, 2008 3:18 am

Just last night, me and my friend had talked about it. What we concluded with our conversation was that, sex is all in man's mind. Now that it can no longer satisfy his mind with what is normal for it, he had moved to a more perverted fashion.

Of course, biologically sexual reproduction is important for the perpetuation of species.
---Just one act of random kindness at a time and you can change the world---
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