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The Problem I Have with Evolution

  1. Dec 16, 2008 #1
    I am no biologist, but I have read a few laymen books on evolution and I have a bit difficulty accepting one part of evolutionary theory, The notion that genetic mutations and genetic variances occur solely by chance.

    It would seem to me, that the evolutionary process would favor organisms which use a responsive mechanism to mutate. This is what I mean experimentally.

    If you have a population of an organism in an environment favorable for that organism, and you allow the population to grow for a few generations, there will be less genetic variance than that same organism in unfavorable environments. My guess is that the rate of genetic mutation would increase in hostile environments. It would seem to me that an organism with such a characteristic would be more likely to proliferate - when compared to an organism which has no such characteristic.

    I want to take this hypothesis a little further though, to expand the possibility that genetic encoding for any generation of an organism reflects the activities of those organisms, so if say, an organism were to perform a certain variety of functions - in this particular hypothetical experiment; the species is feeding on one specific food type, and it's offspring are proficient at eating this food. I would assume the result to show that the same organism is moved into another environment where it feeds on a different food source - the organism after a period of time adjusts and then produces offspring,

    The offspring in the second food source would be born in a higher proportion of having a higher proficiency at digesting that food source and less on the first.

    And the offspring in the first food source would have a higher proportion of having difficulty on the second food source.

    The question I want answered is "are the characteristics of a population of offspring representative of the experiences of the ancestor?"
     
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  3. Dec 16, 2008 #2
    There is an interesting experiment on what I would call "unnatural selection", as it was controlled by man. Here's a link describing it:

    http://www.independent.co.uk/news/s...oxes-turned-into-mans-best-friend-482442.html

    The surprising thing is that merely selecting for a single trait ("tameness") brought about a large number of physiological changes over a relatively few number of generations.

    Don't know what to make of this, but I think it's somewhat relevant to your question. Some of the principal researchers involved say it's completely changed their view of how evolution works. Not that natural selection is flawed, but that the mechanistic explanation (random, slow mutations) of how changes actually occur may be.
     
  4. Dec 16, 2008 #3
    Thanks, That was a pretty interesting link, I don't think it answered my question but it was certainly fascinating. It's almost like certain visual characteristics are correlated with the behavior of the animal - or maybe it is the visual "cute" characteristics which give some physiological bias towards the dog. Say two dogs have the same temperament but one looks cuter; that dog's temperament is perceived to be more docile when compared to the less cute looking dog. Even though they behaved the same.

    I referred that link to a guy who runs www.damninteresting.com. If it's interesting enough, it will be on there. In the mean time, you might want to check it out - there's a bunch of interesting articles on there. It's one of my favorite websites.
     
  5. Dec 17, 2008 #4

    Andy Resnick

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    To some degree, that is undoubtably true- witness the bacteria in our gut. The only way our gut gets populated is by eating. This means the bacteria have to pass through our stomach (pH 1), duodenum, small intestine etc. with all the digestive enzymes present, before coming to rest in our large intestine. Clearly, the bacteria that currently live there have characteristics due in part to the experiences of the predecessors-not the least of which is the ability to co-exist with our immune system.
     
  6. Dec 17, 2008 #5
    So you're saying that this particular bacteria 'chooses' the characteristics of it's offspring based upon the environment it is in?
     
  7. Dec 17, 2008 #6

    Hootenanny

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    No you have it the wrong way round. The environment in which the bacteria exist imposes a set of conditions that determines the favorable characteristics.

    Taking Andy's example and simplifying it somewhat: suppose you have a culture of bacteria and half of the bacteria can survive highly acidic conditions (low pH's) and the other half cannot. When these bacteria pass though the stomach, those that cannot survive acidic conditions will be killed, those that can survive such conditions will live and continue to reproduce and hence pass on the advantageous characteristics to the next generation.

    Therefore, it is the environmental conditions that determine which characteristics are favorable and hence are passed on to the next generation.

    Do you follow?
     
  8. Dec 17, 2008 #7
    Well, let's try to apply it to your question then. This experiment is one of the most relevant there is.
    I would say, based on this experiment, at a minimum:

    (a) The characteristics of a population of offspring are representative of the most favorable traits of the ancestor.

    and taking things a step further,

    (b) The more favorable a trait, with respect to natural selection, the faster adaptation (evolutionary change) occurs.

    Of course feel free to disagree.

    I hope the experiment carries on much longer, I'm sure it will. If so, eventually we may even get a really good take on how speciation actually occurs. That would be amazing!
     
  9. Dec 17, 2008 #8
    Hootenanny
    I understand how evolution is supposed to work, but let's take a supposition.

    You say that half will have characteristics which are unfavorable, and have which do have favorable characteristics.

    Evolution says, that by chance, half of the offspring will have unfavorable characteristics and the other half will have favorable characteristics.

    What I am saying is,
    if that organism is in an unstressed environment, (with a higher PH), it's offspring will be less varied, meaning that the offspring genetic variety may be representative of the experiences of the ancestor.

    Organisms when stressed, have a higher propensity to create offspring with much greater genetic variety.

    Say you take the bacteria out, it has up until this point been in a high stressed environment, if you observe the bacterias replication you will see that the bacteria's genetic variety from generation to generation is greater than if that same bacteria was in an unstressed environment. That there exists some mechanism other than chance.
    That's my hypothesis anyway
     
    Last edited: Dec 17, 2008
  10. Dec 17, 2008 #9
    Your hypothesis is supported by the fox experiment. But the experiment isn't enough to prove it, it's necessary but not sufficient.

    The "high stress" in the fox experiment environment was the breeders favoritism towards the trait of tameness. Succeeding generations of foxes bred in the same environment showed ever increasing tameness characteristics. This clearly isn't chance, but what is it??

    And of course, my favorite question, if this continues will a new species emerge?
     
  11. Dec 17, 2008 #10

    Andy Resnick

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    Evolution does not say "by chance, half of the offspring will have unfavorable characteristics and the other half will have favorable characteristics.". Evolution makes no quantitative statements of any kind. Evolution is a mechanism by which species adapt to their (changing) environment. And at the cellular level, evolution is a mechanism to select for advantageous function- how strongly and specifically a receptor binds to a particular ligand, for example.

    Mutations are constantly occuring and generally have no effect- even in the cells in our own bodies. We have regions of DNA called "SNP"s (single nucleotide polymorphisms) that are highly prone to mutations- this is the basis for DNA 'fingerprinting', IIRC.

    *If* a mutation confers some sort of advantage- specifically, improved ability to reproduce- *then* that particular mutation is selected over time.

    Edit- DNA profiling is based on short tandem repeats, not SNPs.
     
    Last edited: Dec 17, 2008
  12. Dec 17, 2008 #11
    Andy Resnick

    Does it exist though?

    Edit- by "it" I was referring to a mechanism which increases the rate of mutation stimulated by stresses in the environment
     
    Last edited: Dec 17, 2008
  13. Dec 17, 2008 #12

    Andy Resnick

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    Does anything? :)
     
  14. Dec 17, 2008 #13
    Andy Resnick

    I guess you are right about this not being an issue of evolutionary theory, but what I want to know is how do organisms mutate?

    I think we can demonstrate clearly through the right experiment whether such a mechanism such as the one I proposed exists.

    I mean, experimentally - are there any cases where the offspring's distribution has clearly shown a bias towards the environment of the ancestor?
     
    Last edited: Dec 17, 2008
  15. Dec 17, 2008 #14

    CRGreathouse

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    This seems like it would be hard to demonstrate, since offspring can be affected not only by their parents' genes but by the chemical environment of the womb. Even if you were to show that offspring were better suited to their environment than their parents (which seems unlikely -- small changes are the order of the day in evolution, and showing a small change to a good degree of statistical significance requires huge sample sizes) you wouldn't know, a priori if the effect was genetic or epigenetic.
     
  16. Dec 17, 2008 #15
    Reality_Patrol
    I disagree with you, this could be interpreted as just a "by chance" mutation where the differences are compounded over many generations. In each generation, the wild fox will give offspring which are either more tame or more violent, the violent ones die out, because in this environment natural selection favors nice animals.

    It doesn't really qualify as a high stress environment though, what I mean by high stress is an environment where the organism is suffering - shorter lifespan, reduced functioning; That sort of thing. Say in an environment where a fox is starving it may produce offspring in a higher proportion with lower metabolisms.

    The question is, in a low stress environment, would foxes with similar characteristics become prevalent? That is if you were to breed "nice foxes" with each other without selectively forcing the others to death, and without rewarding nice behavior would the same fox breed be shown. - of course, with foxes this would be exceedingly difficult to create such a comparison experimentally, especially due to the wide variety of mutations.
     
  17. Dec 17, 2008 #16
    CRGreathouse,
    I agree with you that in the case of mammals, the amount of variables would likely both lead to a needlessly complex and inconclusive experiment, but say if were were to do the experiment on Streptococcus Auries one which is small enough and reproduces quickly enough to get a suitable sample size, it is also a very adaptable organism.

    In this particular experiment, we will use a stressor,
    We will have say 4 petri dishes, in one petri dish, there is a colony of Streptoccocus which will be left undisturbed,
    in the second dish I will put a low dose stressor in the environment.
    A new stressor will be introduced into the environment over some period T
    In the third I will but a higher dose,
    and in the fourth I will put a near lethal dose,
    Then after a given set of time has passed We will observe the bacteria, and then put them all back into an unstressed environment - seperate from eachother.

    after an interval of T has passed, we will seperate each colony into a division of 10, and then do this again and again.
    We will compare the genetic variety in the colony
    Group A - which came from a no stress environment
    Group B which came from a low stress environment.
    Group C which came from a high stress environment.
    Group D which came from a nearly lethal stress environment.

    It is my hypothesis that groups C and D will have a much greater genetic variety than A and B. This is because environments C and D favored organisms - nearly exclusively - which were highly mutatable.
     
  18. Dec 17, 2008 #17

    Andy Resnick

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    Probably- there's a guy who has incubated E. Coli over thousands of generations, specifically to look at mutations and evolution- look and see what experiments he has performed.
     
  19. Dec 17, 2008 #18
    Do you know the name of the scientist who conducted this experiment?
    I looked up an article on E. Coli and apparently it does show signs of what biologists call "adaptive mutation" very similiar to the hypothesis I brought up.
     
  20. Dec 18, 2008 #19

    iansmith

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    there's such a thing called adaptive mutation in bacteria and other organism but it's being debated whether or not it's true. Briefly, the hypothesis stated that under stress bacteria/organism enter an hypermutatible state which increase the mutation. Most of those mutation are lethal but a few daughter cells would survive and be selected for as being fit.

    http://www.ncbi.nlm.nih.gov/pubmed/...nel.Pubmed_DefaultReportPanel.Pubmed_RVDocSum
     
  21. Dec 18, 2008 #20

    CRGreathouse

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    But that result wouldn't support your theory. It would show that organisms can adapt/evolve, but not that the rate of mutation changes in response to the stress of the environment. The stress kills off enough of the original that various mutants predominantly survive, which causes greater variability. This is just standard adaptation/evolution, and doesn't support (or refute) your variant. What you'd need to show is that first-generation offspring, including those that died after splitting/being born, have more variability in high-stress environments than in low. Once you allow progress over many generations you'd naturally expect the higher-danger environments to have more variability.
     
  22. Dec 18, 2008 #21
    I suppose your right, this would be a difficult experiment to do.
     
  23. Dec 19, 2008 #22
    Chance is a totally valid strategy.

    There are caves where the entire population of species shows signs of once having eyes.

    How could they all lose their eyes?

    It's actually a remarkable demonstration of the wringing out efficiency by selection. Since eyes are useless in a cave, they may actually prove to be a hinderance. They take energy to grow, and they can get infected when damaged. The first member to sport a defect that caused the eye to atrophy would have a slight advantage over others. It may live a bit longer to mate more than the others.

    And so it goes.

    It is why virtually every nook and cranny is teeming with life.
     
  24. Dec 20, 2008 #23
    KAkermann,

    Agreed. But I've struggled to apply chance to the Russian fox experiment.
    Care to give it a go?

    I mean this sincerely. It probably is chance, but doesn't smell like it.
     
  25. Dec 20, 2008 #24
    I don't think its a debate that mutations to our DNA *can* occur entirely by chance (without any adaptative mechanism) that can give an organism a special function which helps it and its offspring survive while others die off (such as a higher affinity for binding and processing a necessary nutrient that suddenly becomes scarce for animals in a certain environment).

    The current problem with "solving" the debate about an organism *also* having an ability to "induce" heritable traits for the specific task of improving ones survival is that we don't have definitive evidence that there are molecules or enzymes capable of performing this function within a cell. The closest thing we've got are some genetic elements (transposons) that can copy certain genes (perhaps preferential or oft used genes) and place them elsewhere in the genome. The way this could lead to adaptative success would be if the organism had some mechanism to select which genes to copy based on how often they are used, etc. You can in fact, interpret observations using this approach, BUT the problem is that evolutionary theory is so broad in its scope that the thinking can always be adjusted to account for the same result.

    Here's an example of what I mean. Take Africa which is basked in sunlight all day. Humans living in such an environment would need the UV/light absorbing skin pigment melanin which is encoded by a gene. In England, the sun is barely present at all and protection against such light is not an issue. Such people could survive and proliferate without needing the same amount of melanin to avert skin cancer as someone in Africa. Hence, you have dark skinned (the "darkness" of a persons skin is related to the amount of melanin a persons body produces btw) people as the natives in Africa (or any other culture whose people live near the equator) and light skinned people living in England (or any other northern european settlement).

    Now there are at least two ways to explain this observation:

    Adaptive - Humans living in Africa used the skin protecting melanin to their benefit and some unknown mechanism copied that gene over and over again within their genome (perhaps using transposons) to ensure that it was handed down to their offspring. Hence, such humans have large amounts of duplicate copies of melanin in their genome. Humans living in England did not need melanin because they were not exposed to the sun. Overtime they copied far less of the pigment to hand down to their offspring which explains how they ended up with light skin and far less copies of melanin in their genome over time.

    Evolutionary theory - Once upon a time there were both light and dark skinned people living near the equator. The dark skinned people had an advantage in that their genomes had randomly mutated to contain more melanin and so they lived whereas all the light skinned people who lacked the extra melanin genes got skin cancer and died out in the area.

    Can you say definitively that either theory is correct or for that matter, incorrect? No, but here is a difference...in evolutionary theory no new scientific observation is needed to explain the result. We know random mutations do happen, and since our ancient anscestors aren't here to correct us, who is to say whether or not long ago there was a mix of people in Africa with vastly different amounts of melanin that widdled down to just one group?

    Of course the adaptative explanation is enticing (it explains for example how *only* people with light skin ended up in northern europe whereas evolutionary theory doesn't have an explanation as to why people with large amount of melanin didn't keep their melanin and proliferate in the north), but without a molecular mechanism to explain how this adaptation comes about it is not science (at least not yet). There are problems with assuming that transposons can perform this role which I will not get into here.
     
    Last edited: Dec 20, 2008
  26. Dec 21, 2008 #25
    All excellent points. You really expressed the issue as objectively and honestly as I've seen it put, on this forum at least.

    To me, good science is about the search for things that can advance the state of knowledge. Even if the search turns out to prove something to the contrary, we all gain a better understanding.

    That's one reason I'm always at odds with "dogma" in evolutionary theory. Yes, random mutations occur and the consequence of that explains a great deal of the observed data. But is that all there is to the story? We're hardly in any position to say so definitively IMO. And no, I'm not a creationist.
     
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