Level of Proof for Evolution

Discussion in 'Biology & Genetics' started by BenTheMan, Mar 23, 2007.

  1. BenTheMan Dr. of Physics, Prof. of Love Valued Senior Member

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    ============DISCLAIMER=============
    I'd rather have this thread die than descend into an anti-Evolution manifesto, as per the other Evolution thread. If you just want to talk about the number of animals that fit on the ark or how the Bible is the root of all wisdom, PLEASE do so elswhere. I invite all people with rational, intelligent thoughts to participate.

    I invite (read: implore) a moderator to remove all terribly disrupting posts into another thread, at their discression.
    ============DISCLAIMER=============


    The disclaimer, of course, won't work. On this I will bet money.

    This is the question. If you are of the school of thought that Evolution must be false because we have never synthesized "life" from chemicals in the lab, what level of proof do you require?

    The issue at the heart of the matter is the nature of "life". If, for example, you only require life to be "self-replicating", then the debate is over---such chemicals have been produced in the laboratory. For example:
    http://web.mit.edu/newsoffice/tt/1990/may09/23124.html
    http://portal.acm.org/citation.cfm?coll=GUIDE&dl=GUIDE&id=782280
    http://www.pnas.org/cgi/reprint/99/20/12733.pdf

    If, however, you have some more complex or stringent definition, you should attempt to justify why this definition is better than simply the requirement that a thing be self-replicating. (For example, does "life" need to be carbon based?)

    The claim is that the simplest life is only self-replicating, and in this sense Evolution is proven. Conversely, if this does not suffice as proof, then any requirements placed on Evolution are too stringent. For example, if one will only accept the appearance of cellular structures in a lab, which are hypothesized to have formed over millions of years, then Evolution will never be proved, as such levels of proof are a priori are untenable.
     
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  3. S.A.M. uniquely dreadful Valued Senior Member

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    I would require the following:

    1. a sign of metabolism: i.e. self sustenance
    2. reproduction: ie species sustenance
    3. adaptation i.e. response to environmental cues that guarantee survival.

    also, does that mean mules are not alive?
     
    Last edited: Mar 23, 2007
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  5. iceaura Valued Senior Member

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    Simple self-replication fails to distinguish living beings from crystals, clays, etc.

    The trouble is that Darwinian evolution can work on things (such as clays) we would not wqnt to call "living". Which is fortunate, in a sense, as it provides a natural bridge between the inanimate and the animate.

    But it removes all evolutionary basis and evolutionary system characteristics from an attempted abstact definition of "living" as opposed to "non-living" entities.

    I doubt there is such an abstract characterization. We have, on this planet, the great nucleic acid lineage and cellular structure. Other places, other times ?
     
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  7. D H Some other guy Valued Senior Member

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    Ben,

    What you are talking about is not evolution. Life is axiomatic to evolution, much as mass is axiomatic to extant theories of gravity.

    What you are talking about abiogenesis. The theory of evolution is concerned with how life forms begets new life forms. Evolution, in my mind, is a fact. It has been observed, both in fossils and in the natural world today.

    Why the nit-picking? Because people who lump abiogenesis and evolution together also pile modern astronomy and geology into that same lump.
     
  8. BenTheMan Dr. of Physics, Prof. of Love Valued Senior Member

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    What does "metabolism" and "self-substanance" mean? I'm certain that some organisms cannot sustain themselves outside of a very sepcifc environment.

    The second point has already been argued above

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    Either the third condition is untenable, as per the original post, or it is already proven in the fossil record. If you want to actually "see" evolution in the lab, then it will never be proven---the natural time scale for these things is on the order of millions of years.

    On mules---they cannot self replicate, this is true. But the requirement of self-replication is not suitable for all life, rather, it serves as a base definition.
     
  9. S.A.M. uniquely dreadful Valued Senior Member

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    Those are the 3 conditions that describe life.

    If an organism cannot survive, it is dead, i.e. no longer alive.

    And you were the one who stressed the self replicate, not me.
     
  10. BenTheMan Dr. of Physics, Prof. of Love Valued Senior Member

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    Well, fair enough. I agree with everything in this statement.

    "Life" has to start somewhere. I am not a fan of God reaching down into the goo and making a bacteria and saying "Go multiply". Most people who object to Evolution cite sciences failure to create something that looks like life in a lab. I want to point out that, at least in some sense, "life" has already been created in labs.
     
  11. BenTheMan Dr. of Physics, Prof. of Love Valued Senior Member

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    Well...yeah. But what does dead mean? Supposedly one could create a molecule which self replicates for an arbitrarily long time.
     
  12. S.A.M. uniquely dreadful Valued Senior Member

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    You'd still be left with a mule that was undead.
     
  13. BenTheMan Dr. of Physics, Prof. of Love Valued Senior Member

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    The point is that the definition of what makes a mule "alive" is hard to extend to a single celled organism, and vice versa. In this sense there cannot be a single definition that covers both life forms.

    Unless you want us to produce mules in test tubes...
     
  14. iceaura Valued Senior Member

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    Darwinian evolution, as the logical structure of a pattern of change, does not require living substrate - anything that self-replicates, varies, and is vulnerable to selection will do.

    Examples: clays, crystals, certain behavioral structures in liquids and gasses (whirlpools, thunderclouds), cellular automata in a computer, etc.
     
  15. S.A.M. uniquely dreadful Valued Senior Member

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    My definition works for both. I can indicate reproduction, metabolism and adaptation for a mule as well as a single celled organism.
     
  16. BenTheMan Dr. of Physics, Prof. of Love Valued Senior Member

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    But I thought mules couldn't reproduce?

    Does it have to do all three or just one of three?
     
  17. S.A.M. uniquely dreadful Valued Senior Member

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    They don't need to self-replicate. One can produce many mules nevertheless.
     
  18. iceaura Valued Senior Member

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    Now that's an interesting notion.

    There are a few beings that don't self-replicate, exactly - viruses the most famous, but some odd parasitic and fungal forms as well, that create some much different form or hijack another being already created to make copies of themselves.

    Suppose mules developed the ability to arrange ass-mare matings, even matings between the very same pair that produced them individually.

    Now suppose snowflakes did the same - created conditions, such as cool air masses at high altitudes and meltwater pools at low - in which more snowflakes would be formed.

    Where's the distinction line?
     
  19. S.A.M. uniquely dreadful Valued Senior Member

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    The metabolism and adaptability?
     
  20. valich Registered Senior Member

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    sounds like your trying to mix biology with philosophy. can't tell what type of answer you're searching for
     
  21. aaronmark Registered Member

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    An interesting tangent: A mule in Morocco was able to successfully reproduce despite its odd number of chromosomes.

    news.bbc.co.uk/2/hi/science/nature/2290491.stm

    I'm sure there is a more intelligent explanation somewhere, but it seems that species which can interbreed (lion & tiger, horse & ass) descend from a common root species, and have, through natural selection, arrived at their various subspecies.

    More on the subject: Natural selection seems to be an obvious means of evolution, however, it only deals with the dominance of existing genetic traits. What is not apparent to me is where and how new and more complex genetic material comes into existence.

    The only examples that come to mind of mutation (that introduces new genetic material) causes the organism to become sterile and less capable of survival. This seems problematic to the theory of evolution as I understand it.
     
  22. Fraggle Rocker Staff Member

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    Anyone who demands proof of a scientific theory is not a scientist because he doesn't understand the scientific method. Mathematical theories can be proven true because they involve only logic and abstractions. Scientific theories are about the natural universe and are only predictions of its future behavior derived logically from empirical observations of its past and present behavior. At any time in the future of the natural universe, any scientific theory can be disproved by the emergence of a good counterexample.
    It sounds like you are committing the most common mistake of the creationists and evolution denialists themselves, which is to confuse evolution with abiogenesis. The theory of evolution does not speak to the origin of the first lifeform, but only to the transformation of one existing lifeform into one or more others. Abiogenesis is the hypothesis that living matter arose naturally from non-living matter. The evidence for it does not have the same strength as the voluminous and multifaceted evidence for evolution. Basically all we've got is good but not great evidence that the universe started out as a blob of obviously non-living matter and energy and ended up with at least one planet full of living matter, so the transformation must have occurred at some point but we don't know how. Still this puts abiogenesis in the lead over creationism, because all the creationists can muster as "evidence" of their hypothesis is the relative lack of evidence for abiogenesis. Basically their argument boils down to: "You scientists have not yet been able to explain abiogenesis, so that is proof of the existence of a supernatural universe." This statement violates the scientific method in so many ways that it is hard to take seriously.
    Anyone who reads sci-fi or watches it on TV is familiar with the hypothesis that life can be based on something other than carbon and DNA. Silicon-based life is a sci-fi cliche since it's so easy to map carbon chemistry one row down on the periodic table, into silicon chemistry. Carbon-based life arose on earth because the conditions are right for it. Life that arises in the conditions of a gas giant or a neutron star would have to be quite different. James P. Hogan and Robert L. Forward are professional scientists who write well-researched sci fi, and they have created some very interesting lifeforms for non-earthlike conditions.
    To reiterate, you're talking about abiogenesis rather than evolution. But it also seems that you're talking about proof of concept, which is a business term rather than a scientific one--since scientific theories can never be proven. In business, proof of concept is, "Can we do this with the time and resources available, and if we do it will it more or less satisfy the requirements we've been given?" To make an analogy to science, I suppose it would be something like, "If we can find evidence of [a certain condition or process], will it support our hypothesis and make it difficult to disprove?" In other words, if we achieve the Holy Grail of Abiogenesis and create life from non-life in a laboratory, will this be sufficient support of the theory that life arose that way naturally, so that the creationists will crawl back into their holy books and leave us alone?
     
  23. aaronmark Registered Member

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    Hey, Fraggle Rocker. You seem to know a lot about this. Do you know of any studies (in the wild or in the lab) where scientists have observed a positive mutation? (Meaning, a mutation resulting in the introduction of new genetic material [not natural selection] to a species that was not fatal, deforming, or sterilizing and helped it to survive better in its environment.)
     

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