The replicator (first version of the selfish gene)

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ragav.payne
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The replicator (first version of the selfish gene)

Post by ragav.payne » Tue Aug 28, 2007 6:12 pm

Hi,

I've just started reading this book called "The selfish gene" and in the chapter "The replicator", it says that out of an utterly improbable event, replicators (molecules that could replicate themselves) emerged in the soup where molecules were constantly trying to attain stable configurations. Fine.

But, why did these stable molecules(replicators) have to die out?


This is the way I understant it :-

First their parent molecules make the building blocks cling along with them and then the offspring molecule gets detatched and then does the same and then some mistakes happen in the replication process (evolution).

Which part of the phenomenon seems suggestive of the necessity of these molecules to cease existing? Why couldn't they have infinitely built up in no.?

Did the stability of the replicators time-dependent? Or was it resource dependent? If so, why?

Regards.
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rAgAv

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Post by alextemplet » Tue Aug 28, 2007 8:41 pm

Perhaps a mixture of both. The molecules may have naturally decayed over time. Perhaps they used certain resources to slow this rate of decay, much like modern-day organisms constantly utilize nutrients to repair their aging bodies. If those resources run out, death is never far off.
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Post by greeneye55582 » Tue Aug 28, 2007 9:10 pm

Outside influences, lack of resources, inability to "adapt" to changed environmental factors.

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Post by Darby » Tue Aug 28, 2007 9:16 pm

And what about molecules that "improved"? Couldn't they outcompete ancestral holdovers for resources?

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Post by greeneye55582 » Tue Aug 28, 2007 9:31 pm

Or is the whole point that there were no "imporovements", no real evolution. Simple replication, simple copies.

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Post by ragav.payne » Wed Aug 29, 2007 4:32 am

greeneye55582 wrote:Outside influences, lack of resources, inability to "adapt" to changed environmental factors.


If it were the changed environmental factors, then the entire species of molecules would have been wiped out. The erasure of species wouldn't be at a specific rate.

For the environmental changes to have caused the "death" of the individuals in the species, the rate of evolution of the species would have to be higher than the rate of change of the environment.

Anyway, why should molecules "age"? As I see it, these molecules are nothing but stable configurations of "building blocks" that are floating in the sea. Is it because, the strength of the bonds weaken after a specific time? Do these bonds decay over time? Why would they "decay", if there was nothing to break these bonds down?


alextemplet wrote:Perhaps a mixture of both. The molecules may have naturally decayed over time. Perhaps they used certain resources to slow this rate of decay, much like modern-day organisms constantly utilize nutrients to repair their aging bodies. If those resources run out, death is never far off.


It is not apt to compare these primordial molecules with the protien rich present day organisms. They have to be understood using some simple chemistry.

And if the resources run out, then the entire species of molecules would have to be erased.

Now, I have a new question - Why do "we" age and die? May be we can apply the analogy to these molecules.

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Post by greeneye55582 » Wed Aug 29, 2007 6:47 pm

Well we can start with the telomeres at the end-caps of our chromosomes that are degraded over time as we age. More degredation = valuable pieces of DNA lost = a variety of different problems. And cancer cells don't seem to have this problem. The telomerase continues to "add on" or protect the telomere of the DNA in cancer cells, so in that aspect they can continue proliferating.

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Post by ragav.payne » Thu Aug 30, 2007 5:32 am

I think I got it - replicators would live infinitely if not for the rival species of replicators that compete with them for resources. The ones that do not evolve get reduced to building blocks by the rival replicators and the reduced products are used up.

Sounds sensible to me. But, there's one thing that still boggles me - Do the individual replicators of the same species destroy each other for reproductive resources? After all, their only function is to replicate and if it is possible to obtain resources for that through reduction of same type of molecule, why not do it? I think this is what Richad is talking about. The individual genes are selfish. (hurray! I got the whole point of the book after reading the first chapter)

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Post by greeneye55582 » Thu Aug 30, 2007 5:40 pm

Are you reading Dawkins?

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Post by ragav.payne » Fri Aug 31, 2007 3:20 pm

>Are you reading Dawkins?

Wow! I wish I could do know how to do something like that. But, i'm just reading Dawkin's book - The selfish Gene. After I read the first chapter, I bought all his other books. I'm now reading the rest of the chapters of the selfish gene.

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Post by Darby » Sat Sep 01, 2007 1:43 pm

Part of the problem here seems to be the use of "environment" as a global parameter, but changes in a molecule's environment can be just changes in nanometer-sized areas. Any variation in a thousand different environmental factors over tiny distances (or not-so-tiny distances) could affect the viability of a given evolving molecule.

It may help to imagine that once a soup of complex, self-replicating, resource-consuming molecules starts to arise out of chance encounters driven by available energy, you wind up with a somewhat recognizable ecosystem. There are advantages available from cooperation, organization, isolation, synthesis, even predation, that could drive a soup of individual molecules to clusters of cooperative molecules to clusters semi-isolated within bubbles of "soup scum."

What of the original molecules? They probably became incorporated into more complex systems (think how the carbon that is in you was once in that soup, or a dinosaur, or a fern), but even if some of those molecules survive to this day in the oceans, no one is really looking for them. How would you recognize them distinct from, say, metabolic "leftovers" from dead organisms?

Personally, I believe that the closest thing to those original molecules that we've recognized are viruses, but even they are very complex systems.

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Post by alextemplet » Sat Sep 01, 2007 3:53 pm

Darby wrote:Personally, I believe that the closest thing to those original molecules that we've recognized are viruses, but even they are very complex systems.


And viruses depend on more complex cells to survive, and so could not be the original molecules that existed entirely on their own. I once read that viruses may have evolved from parasitic cellular organisms that reproduced inside their host cells, and thus gradually lost the ability to reproduce on their own and became the viruses we know today.
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