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Thread: The Beginning of Evolution

  1. #1 The Beginning of Evolution 
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    It is estimated, that life arose from molecules with the ability to copy themselves (replication). Does evolution start from the very same moment when any molecules obtain this ability? Or are there certain other conditions, like increased susceptibility to chemical damages so that mutations can occur? Do they have to be complex or could simple molecules also replicate and start evolution?

    Is it possible, that life arose several times independently, but only one molecule type prevailed (-DNA) and the others became extinct?


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    Forum Cosmic Wizard i_feel_tiredsleepy's Avatar
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    Natural selection should apply to any replicating system that allows change to occur. It is not per se exactly the same as the theory of evolution, which applies solely to life once it exists.

    As to different possibilities, yes it could have happened, but it is difficult enough to answer how the DNA thing happened without thinking about other possibilities.


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    It is estimated, that life arose from molecules with the ability to copy themselves (replication). Does evolution start from the very same moment when any molecules obtain this ability? Or are there certain other conditions, like increased susceptibility to chemical damages so that mutations can occur?
    You are asking about how one would want to define "evolution", and that will be easier when, or if, the actual physical history (or a limited set of possibilities) has been better established.

    Some people hypothesize that the foundation context was a complex of self-replicating clays (these exist) forming an accretion base for complex carbon based oily stuff.

    Probably no special arrangement fostering variation was necessary - variation and "error" is easily come by in the big world. Current mutation rates are too high, for successful reproduction, and living beings possess special mechanisms for repairing and minimizing replication mistakes.
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  5. #4 Re: The Beginning of Evolution 
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    Quote Originally Posted by neird
    It is estimated, that life arose from molecules with the ability to copy themselves (replication). Does evolution start from the very same moment when any molecules obtain this ability? Or are there certain other conditions, like increased susceptibility to chemical damages so that mutations can occur? Do they have to be complex or could simple molecules also replicate and start evolution?

    Is it possible, that life arose several times independently, but only one molecule type prevailed (-DNA) and the others became extinct?
    The boundary between abiogenesis and evolution is hazy, and depends largely on how you want to define life.
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    WYSIWYG Moderator marnixR's Avatar
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    there's some who would define life as chemistry that exhibits descent with modification
    which would mean that the beginning of life on earth and the beginning of evolution are one and the same thing
    "Reality is that which, when you stop believing in it, doesn't go away." (Philip K. Dick)
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    Thanks for the interesting answers.

    Quote Originally Posted by i_feel_tiredsleepy
    Natural selection should apply to any replicating system that allows change to occur. It is not per se exactly the same as the theory of evolution, which applies solely to life once it exists.
    Yes, you are right. I often forget this. Natural selection is one of the main causes for evolution.
    But what properties must such a replicating system have? Obviously they must be very complex, otherwise replicators would arise each day... Were such self replicating molecules ever created by humans? I heard that the RNA was the main information and replication system at first, as it can catalyse its own replication. Later it was abolished by DNA, with enzymes for catalysis for replication etc. RNA is already very complex. Could there be any predecessors?
    And why applies the theory of evolution only to living systems?

    Quote Originally Posted by iceaura
    Some people hypothesize that the foundation context was a complex of self-replicating clays (these exist) forming an accretion base for complex carbon based oily stuff.
    Yes, I also heard about that theory. In fact, they would not increase the probability of synthesis of replicating carbon systems, because the formation of complex organic molecules does not mean that they will be self replicating. And why did they go extinct? Were their products -the carbon replicator- more successful? Or did they slowly turn into the carbon replicators? But why are then no characteristics of clay, as silicon, left any more?
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    Quote Originally Posted by neird
    In fact, they would not increase the probability of synthesis of replicating carbon systems, because the formation of complex organic molecules does not mean that they be self replicating.
    Why wouldn't the formation and repeated replication of complex organics make the emergence of independent replication (need not be "self") more likely? Seems like it would.
    Quote Originally Posted by neird
    And why did they go extinct?
    They didn't. They're common.
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    Quote Originally Posted by iceaura
    Why wouldn't the formation and repeated replication of complex organics make the emergence of independent replication (need not be "self") more likely? Seems like it would.
    Ok, you are right. But these organic molecules have turned into self-replicating molecules, sometime (-> DNA).
    By producing more not-self-replicating organics the probability of the formation of self-replicating organics is increased, because the not-self-replicating organics are more common. Do you mean this? I would agree with that. But the clay itself does not contribute to the arise of the self-replicating ability apart from that.

    Quote Originally Posted by iceaura
    They didn't. They're common.
    But wouldn't they then be a kind of lifeform, coexisting with us? Where do they occur?
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    Quote Originally Posted by neird
    But wouldn't they then be a kind of lifeform, coexisting with us?
    They are nowhere near that complex. Neither are other self-replicating structures, such as rock crystals.

    The most common mechanism of self replication in the inorganic world is simply breaking into pieces, each of which grows by accretion into a version of the original. Clays, for example, will form in ephemeral puddles, dry out and crumble and blow away in small pieces, and seed other shallow pools of water with their particular spiralling accretion pattern or arrangement of surface molecules. They vary in the size pieces of the crumble, the likelihood of the proper chemicals and such in the new puddle, the speed at which they grow, etc - there are grounds for selection. We see that even in living beings now - and often with an "outside loop" component, some contribution from otherwise unrelated features of the environment, even distant in time or space.

    Also. in the time before bacteria and other hungry beasties, the nonliving world would have exhibited much more complex forms and structures than it does now. Much more in the way of complex substrates was once available on the planet's surface.
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    Forum Cosmic Wizard spuriousmonkey's Avatar
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    Quote Originally Posted by marnixR
    there's some who would define life as chemistry that exhibits descent with modification
    which would mean that the beginning of life on earth and the beginning of evolution are one and the same thing
    I concur. I don't see any logic in the possibility of having a beginning of evolution/life without evolution.

    Because without evolution there is just stasis. Without any descent with modification I don't see how any process could make the transition from a collection of chemicals to an evolutionary process. Life started with life. Evolution started with evolution. And the initiation point of evolution is per definition descent with modification in a somewhat reliable manner.
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    Quote Originally Posted by marnixR
    there's some who would define life as chemistry that exhibits descent with modification
    which would mean that the beginning of life on earth and the beginning of evolution are one and the same thing
    Am I reading this right? Evolution can be defined, by some, as beginning with a chemical reaction that causes more of the same chemical structures to be produced? If so, it's along the lines of my current layman's perspective on the evolution of life.

    And if change in chemical structure and replication is evolution, then can we apply this to energy solidifying into chemicals to produce what we call matter? I'm not even sure if that's possible, but I pose the question out of interest.
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