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Do our senses direct what our DNA should change

  1. Jul 23, 2014 #1
    I recently read this article that one guy here on the forum wrote few years ago:

    "Evolution knows nothing. It has no direction or knowledge about anything. Natural Selection drives which random mutations in the genetics of a population are left to be passed on to the next generation. If a change in genetics favors one individual, that individual is more successful at reproduction. Over many generations the traits that confer success become more common."

    The rest of the conversation betweene useres was that nothing directs evolution. That there is only random variaton plus reproduction that is important. This word RANDOM variation is what bothers me

    Why then does camel in desert dont lose time on growing wings? Why does a bear in the woods never had wings? At least one bear.
    Why dont bird develop water supplies?

    Because they dont have to. And how do animals DNA know what would benefit them?
    It gets feedback from senses.

    I go a little bit in the extreme but you get my point.
    It seems to me that the body when comes to new enviorment in order to survive looks inside its resources to find the way tu survive. If there is no one, DNA starts the slow change.. To cold? To hot? Nothing to eat? Hard visibility? Let give this animal what it needs.

    What do you think? Does this have any sesne to you? Is it change in the DNA major triggered by our senses? Does the DNA give us and develop for us just what we need?
  2. jcsd
  3. Jul 23, 2014 #2


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    That is not how evolution works. DNA doesn't "know" anything. It's just a large molecule that acts as a store for mRNA templates, that's it. The expression of genes is contextual based on intracellular biochemistry which is mediated by the cell's environment. The interaction of the products of these genes determine cell morphology and behaviour.

    The problem I think you're having is in understanding how random mutations lead to adaptation, is this correct? The answer to that is selection. When an organism reproduces its offspring gets half of its DNA (the other half from a partner normally) and some of this DNA will be randomly mutated. These random mutations can give rise to slight differences in the offspring compared to the parent. In of itself that doesn't mean much but some of these mutations might give be beneficial to the offspring's survival and reproduction. E.g. a mutation in a gene responsible for hair pigmentation that makes the offspring slightly more camouflaged. Because this offspring has a slightly higher chance of surviving and reproducing compared to its peers the next generation will feature a higher prevalence of the advantageous gene. Do you see why?

    We have a primer for evolution that you might like to read:
    Last edited: Jul 23, 2014
  4. Jul 23, 2014 #3

    Simon Bridge

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    Welcome to PF;
    "random" is not a good word to describe how evolutionary change works.
    You are correct, it is not random in the sense you are thinking of.

    But first observe more carefully: the camel and the bear both have "wings" in the evolutionary sense.
    Wings are a specialized kind of arm and both have arms - they just cannot use them to fly.
    Many flightless birds are in the same boat.

    Wings are not strongly favored by evolution - as shown by how fast birds lose their ability to fly when there are no predators to bother them much. Bears and camels have other approaches for dealing to predators, so they don't need wings. They cannot produce them spontaneously because those are many steps away - they'd have to get smaller to start with. Basically they wouldn't be bears etc any more.

    Evolution works in increments. Wings are too-big-a change.

    Evolution has to work with variations of what is there already... large fat deposits would hinder a bird when it comes to flying so desert birds don't develop humps like camels. However, they do need some strategy to deal with arid conditions. Fortunately there are many strategies for dealing with life's adversities.

    The "randomness" the posts were talking about is the distribution of a trait.
    For instance, heights are randomly distributed in humans. What height a child grows up to be is random ... though we can make a good guess about what range of heights are likely.

    If there were some outside influence that favored taller people, so that taller people have a reproductive advantage, then the next generation would end up taller on average ... with the heights still randomly distributed.
    Seewhat they mean - the heights of any particular individual is random in the sense of being randomly distributed, but the change in average height between generations is not completely random, but determined by something else. (Maybe a disease comes along that targets people under 5 feet tall?)

    The passage is pretty much one-way too - especially with speciation.
    Smilodon was not able to devolve into short-toothed cats once their prey died out, instead their position as apex predator was taken over by other animals when they died out too.
    Mammals have returned to the water, but they didn't turn into fish.

    So the DNA does not need to know what would benefit the species.
    If the DNA produces something that is not a benefit, then the species dies out.

    I'll second the evolution primer.
  5. Jul 23, 2014 #4
  6. Jul 23, 2014 #5

    Simon Bridge

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  7. Jul 23, 2014 #6
    >Well, the main feedback takes the form starvation and predation - so you can say that the >feedback for not being able to deal with a predator is said predators teeth.
    >Evolution does not happen to individuals, but to groups.

    >Sure - no argument there. This is the same as it is "like" there is something pushing the planets >around the Earth so they know just where to go. So what?

    >Have you read the primer on evolution yet? It deals with these questions.[/QUOTE]

    Now i realized that i am not interested in evolution through reproduction. When by reproducing kids get some new features that can help them or not. I understand that.

    I am more interested in the other aspect of evolution, when enviorment defines the change.
    I quote wikipedia:
    "The forces of evolution are most evident when populations become isolated, either through geographic distance or by other mechanisms that prevent genetic exchange. Over time, isolated populations can branch off into new species.[3][4]"

    My point is that enviorment sets the rules. Species must adapt or die out. If you dont change you go away. The individuals that start to change, have better chance to live longer, reproduce and make better population.

    That is why some birds on some island have strong beak, and some on other islands where food is not hard, do not.
    That is why some monkey see in color, so he could eat green fresh leaves, and not red old leaves.

    That is why somebody who trains running, gets stronger muscules in legs, and somebody who trains arm lifting gets stronger arms. Enviorment sets the rules. People adapt, or give up, die out.

    Give a time in equation and you have more immerse effect. Whole population change in attributs.

    How does a body know that it must improve beak, or give a monkey color vision?
    Because it gets some kind of feedback. There is something in the organizam that limits random variation on useful stuff that the individual in harmony with enviorment needs.

    I see that pretty important. Othervies instead the beak DNA would maybe go first with better wings. Or instead to help a monkey to see better, it would improve his muscles..And that is not what some enviorment asks from them.

    I am aproching this from the amateur stance. But what i wrote above does happen in nature.
  8. Jul 23, 2014 #7


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    I'm sorry, but I must repeat - again - that what you are suggesting does not happen in nature.
    There is no "other aspect of evolution". Evolution happens because the environment causes the selection changes over a period of many generations. Individuals in a species don't make changes in their DNA on the fly and none of the changes are ever biologically directed (on purpose). They are all accidental.

    With one caveat, of course: humans have become capable of altering their DNA on the fly. But that isn't typically considered a part of "natural" evolution. It's a completely different issue and isn't what you are describing.
  9. Jul 23, 2014 #8


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    The parent(s) may exercise and develop stronger muscles as a result.
    Do you honestly believe that the offspring ( babies ) of such a parent(s) are born with bulging muscles? and then would become just a strong without training in adulthood as the parent was?
  10. Jul 23, 2014 #9


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    That was the basic idea of http://en.wikipedia.org/wiki/Lamarckism, which is pretty much dead and buried in that simple form.

    On the other hand, http://en.wikipedia.org/wiki/Epigenetics is alive and well.

    But if the OP is arguing that animals somehow "know" what features need to be "improved", how does he/she explain how plants evolve?
  11. Jul 23, 2014 #10

    Simon Bridge

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    Um - technically there are mechanisms that limits the extent that a mutation can happen.
    You don't spontaneously grow wings in one generation no matter what the environmental pressures.

    But that has already been answered.
    The offspring only get two sets of genes (one from each parent).
    Large random mutations will kill the offspring... so big sudden changes are dead in the water.
    Your question becomes: how does this come about.
    Answer: natural selection. The big mutations kill the offspring!

    In simpler organisms, there is a wider scope for mutation - take flu for example.
    But there is always a balance - if an organism mutates too much too fast, it dies out; but if it mutates too little it also dies out. Initially there was greater variety of mutation, but the ones who mutated outside the balance range died out. Thus modern organisms are the offspring of those who mutate in between.

    There are other, more subtle, mechanisms too.
    But this counts as the fine detail on the theory.
    You have to learn to crawl before you can walk - I see no evidence that you have read through the primer on evolution that you have been repeatedly directed to. It answers a lot of the questions you have been answering.
    Until you get the basics of natural selection down, you are unlikely to be able to understand the finer details.

    Acquired characteristics being passed on to the offspring is an earlier version of evolution called "Lamarckism".
    See: http://en.wikipedia.org/wiki/Lamarckism

    But this does not happen in nature - i.e. the finch does not know it needs a heavy beak for seeds - all it knows is that there are seeds to eat. Those finches with heavier beaks than the average do well on that island, the others move away where the food is easier to get at or they die out. The result is a finch population with slightly heavier beaks. Repeat this for a few thousand generations and the average beak is a pretty good seed-cracker. If all the seed plants died out suddenly, those birds would starve.

    So you see, there is a feedback mechanism telling the bird population (not the individual bird) what shape beak is "best". The feedback is emigration, or starvation and death for those who don't have the right beak.

    It's like taking an exam where you are told to write whatever you want and nobody tells you how the paper will be marked. After all the papers are marked and the scores tallied you can figure out what gave the high scorers the advantage, but the individual people did not know what the advantages were. Its the same in Nature - it's like we are constantly being tested in the most unjust way possible and we are trying to figure out how the organisms who passed (the ones alive today) managed that feat.

    Evolution is to biology what quantum mechanics or relativity is to physics - you cannot expect to grasp everything in one go, you have to work at it.

    Do read the evolution primer.
    If you do not follow advise we cannot help you.
  12. Jul 23, 2014 #11

    Simon Bridge

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    All evolution is through reproduction. There is no other kind.

    Many species have evolved so that individual members can change to better fit their environment and they can also modify their environment to fit them. Humans seem to be particularly good at it... so far.

    That is not evolution - it is another trait that is governed by evolution.

    Evolution does not happen to individuals, but to populations.
    If you don't have what it takes to survive, you die out.
    If your kids have managed to score some mutation that helps them survive, then your kids will continue.
    That is how evolution works.

    You say you understand about some kid getting a trait that is an advantage.
    Well, the environment is what sets the rules for which traits are an advantage.

    Some kid may be born a naturally strong swimmer - this is no advantage if they live far from large bodies of water. Environment - see?

    This is in the primer. Read it.
  13. Jul 24, 2014 #12


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    I wasn't thinking of the Epigenetics side of it, but rather the cytoplasm and related, and how the environment can have an influence. Perchance the OP had a good resource, from what was being written.

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