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Chances for life to have ever been created

  1. May 30, 2003 #1
    in probobility like terms, what are the chances for life to have ever been created. i mean, have you ever thought of the sheer improbobility of it, for the first singled celled organism to form? it would probobly have to include (just by the random fall together of molecules) a digestive system, and a reproductive system, as well as the ability to move (unless that was later), but still, it's amazing! And it would be hard to believe that all life sprung from this single anomaly of order through disorder, there would be so many dangers that it would probobly kill this Adam and Eve of all life. luckly the earth is a pretty large staging ground for this to take place so i guess it's sort of "bound to happen".
     
    Last edited by a moderator: Feb 5, 2013
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  3. May 30, 2003 #2
    Re: life

    Wouldn't the only requirement be for two cells to run into eachother? From there evolution takes over to create, after many millions of years, what we are today?
     
  4. May 30, 2003 #3

    FZ+

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    I think an obvious hole in this is that:
    life itself is not special.
    life as we know it is especially not special.
     
  5. May 30, 2003 #4
    The mathematician John Von Neuman

    showed that there were five requirments for a self reproducing system. For life as we more or less know it to occur there is one requiment that needs to be added to his, that it be able to evolve. So life really doesn't need all the things you've listed, just those six requirments and it will in time evolve the others.
     
  6. May 30, 2003 #5
    Re: Re: life

    you aren't understanding my meaning. what is the chance for a cell (the first cell!) to have ever been created?
     
  7. May 30, 2003 #6
    Re: Re: Re: life

    Depends on how you look at it. You could take every imaginable factor and get it pretty near zero. Or you could take it logically and see obviously it has to be a 100% chance of happening:wink:
     
    Last edited: May 30, 2003
  8. May 31, 2003 #7
    Odds are fantastic

    The simplest living organism that we know of is Mycoplasma genitalium.
    This organism can't survive on its own though, it's parasitic.

    http://www.edwardwillett.com/Columns/manmadelife.htm

    We're still trying to determine the minimum number of gene products necessary for life. Even if it turns out to be as low as 250, the odds against it occurring through random chance would be fantastic. To give an idea of the extreme fine-tuning in living systems, just take a look at sickle cell anemia. This disorder is caused by a change in only one nucleotide base.
     
    Last edited: May 31, 2003
  9. May 31, 2003 #8
    Im with you all the way maximus.. I too would like to know how it is that even if we can accept that one cell /atom whatever, could evolve to this point of diversity of life.. How is it that that first cell/atom existed???..

    Hmmm
     
  10. May 31, 2003 #9

    FZ+

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    Re: Odds are fantastic

    As I said, this is only significant if we say that life is somehow special above non-living things, and "should" occur.

    If I drop a pen, the positions it lands in are astronomical. Very slight winds, turbulence, variations in the gravitational field, quantum effects, electromagnetic induction with that little clip thing, photonic pressure mean that there are far more than 2^250 possibilities for how it would land. Yet it does land in one of these 2^250 positions, each with 1/(2^250) probability. Do we argue then that the way this pen fell is not random chance? No.

    It also misses that a parasite is in fact more complex than ancient life forms, as it requires all sorts of protein markers to identify and defend itself from the host. And that sickle cell anamia is only applicable to very complex organisms, and even that is definitely non-fatal.
     
  11. May 31, 2003 #10
    The probability of the pen landing in any position is of course 1. In your example above, the total number of pen positions we are looking for that would indicate a "success" is equal to the total number of possible pen positions. If we take the ratio of successful pen positions to the total number of possible pen positions, we get 1 or a 100% chance of success. So by your analogy, any sequence of DNA will produce functional proteins capable of sustaining life, since any sequence we can come up with would represent a "success".

    Why then does it have the fewest number of genes?
     
  12. May 31, 2003 #11

    iansmith

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    Because it is a parasite. Having fewer genes doesn't mean that it is more simple. Some of the function that are require for survival migth be taken over by the host. Therefore the less usefull genes will be lost in order to reduce the amount of energy require for replication and survival. FZ+ is rigth, parasite are more complex than some other early life form but Mycoplasma genitalium has become a couch potato. Genome reduction is also seen in many pathogen such as Mycobacterium.
     
  13. May 31, 2003 #12
    Dude, I am not following your logic. Where do you get a 100% chance of sucess from? What are "successful" pen positions? FZ's analogy does not in any way suggest that any sequence of DNA will produce functional proteins. In order to understand it, you have to realize that life is not "special", and that it doesn't need good odds to occur any more than the pen needed good odds to land in any one position. The comparison is comparing the 1 position that the pen ended up in to the existence of life.

    Do you know how many genes ancient life forms had?
     
  14. May 31, 2003 #13
    I don't really know much about this, but currently AFAIK the idea is it happened like this:

    The early Earth was an "organic soup" full of various carbon-nitrogen-oxygen compounds, produced by well-known processes. Under conditions like those believed to exist at the time (~4 billion years ago) more complicated organic molecules will spontaneously form, among them RNA.

    Now, certain types of RNA are known to be self-replicating, and furthermore they can catalyze a surprisingly wide variety of chemical reactions. So the earliest type of 'life' was probably self-replicating, autocatalyzing strands of RNA. Evolutionary pressures then kick in on the nucleotide sequence of the RNAs.

    The main things needed are some version of a ribosome, the organelle that makes protein from RNA, and a copy mechanism. Tellingly, ribosomes are largely constructed of RNA themselves. Once you have those, you can manufacture proteins and enzymes; and it's not too hard to imagine how the other organelles might have developed from simple protein systems. At some point the shift to more-efficient DNA took place (the necessary enzymes are quite simple, what you find in retroviruses.)

    This is called the "RNA World" hypothesis... googling that should give you a ton of info. There is a book of the same name with a survey of detailed research into possible development pathways, it's pretty cool stuff... I've been meaning to learn more about it eventually.

    The simplest living critters in today's world -- prokaryotes -- aren't that complex. They have no reproductive/digestive systems or anything like that; basically just DNA, ribosomes, a cell membrane, and some enzymes...
     
  15. Jun 1, 2003 #14

    Phobos

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    maximus - The first self-replicating thing was not a one-celled organism. There were less complex stages before that. Those less complex, self-replicating molecules were subject to mutation and selection. At some point, they came together into a cell (consider a bunch of molecules that are hydrophilic at one end and hydrophobic at the other...they can naturally glom together into a sphere in an aquatic environment...that leaves an open space in the middle for other molecules to set up camp). Symbiosis.

    When is it called "life"? Well, it's probably a gray area. We can't even agree when human life starts! (birth? 1st trimester? conception?)

    What is the numerical probability? Can't be calculated now...there is no well-supported scientific theory as to how abiogenesis actually occurred. No theory (explanatory model), no calculations of probability. No other examples of worlds with life (or at least a small data set)...no statistics.
     
  16. Jun 1, 2003 #15

    Phobos

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    Re: life

    Who's to say there wasn't more than one false start?
     
  17. Jun 1, 2003 #16

    Phobos

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    Re: Odds are fantastic

    It is incorrect to assume that the first lifeform ever is the same as the simplest modern lifeform which has had billions of years of evolution behind it.

    Defining "life" is nebulous. Is 250 genes "alive" but 249 is "inanimate"? Whatever we define as "alive" can still have non-living self-replicating molecules as an ancestor (unless we define life as the first self replicating molecule...but that doesn't sound right).
     
  18. Jun 1, 2003 #17

    Phobos

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    I don't know about you, but many creationists seem to think that there is only 1 successful pen position. Not only that, but only 1 possible successful pen position on a subsequent flip...and another and another and another...

    Which when calculated results in astronomical odds against such a line up. But the missed point is that there are many possible positions that are successful. The path we took is not preferrential. (Or if it is, it was certainly made to look like it isn't! :wink:)
     
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