Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

How does DNA know when to evolve

  1. Jan 27, 2010 #1
    It is proven, populations evolve when they enter a different environment.

    When you as a half-fish half-amphibia want to explore land you need lungs not gills,
    your heart and your whole body must evolve to survive in the new environment,

    No dehydration in the water but pure dehydration in the new environment,
    just solve the problem by evolving ...

    But how does the Dna know when to evolve a different heart, lung etc. ?
    Is it the genes (and amino acids and proteins in them) "controlling" the heart that see this ?

    I know the evolving is given from offspring to offspring and spread all over the population,
    but i dont know how they know when to evolve.
     
  2. jcsd
  3. Jan 27, 2010 #2

    tiny-tim

    User Avatar
    Science Advisor
    Homework Helper

    Welcome to PF!

    Hi questiner! Welcome to PF! :smile:
    DNA evolves all the time, but most of the changes are useless or worse than useless.

    Occasionally a change happens that is useful (like a different lung), and then that particular individual breeds more successfully than others, and the change spreads.

    See http://en.wikipedia.org/wiki/Evolution#Mutation" for details of these continuous random mutations. :wink:
     
    Last edited by a moderator: Apr 24, 2017
  4. Jan 27, 2010 #3
    Or something can live in water so that the animal can get a swimming body, like how the whales moved into water, while they were a land animal, kind of like a dog, and now has a swimming body from living in the water for a long time.
     
  5. Jan 28, 2010 #4
    That was great post to read. Highly informative, i'll visit this more often.
     
  6. Jan 28, 2010 #5
    I would think that the DNA doesnt so much 'know' when to evolve, but rather, there was an accident in mutation and this accident or blunder was passed onto a portion of the offspring and it enabled them to survive a certain enviroment. The ones without the mutation just died off cos they didnt have the benefit of the mutation to help them...and the ones with it survived , and soon enough the ones with the beneficial mutation became the norm.
     
  7. Jan 28, 2010 #6
    Re: Welcome to PF!

    thanks for reply.

    I know about beneficial mutations and harming mutations, and i know that the natural selection "votes" these mutations. Especially when its goal is more offsprings that help the population to survive longer in its environment (survival of the fittest).
    But this is not the question.

    My question was like (analogy):
    If you want to move your hand, you brain sends electric impulses to the hand.
    And if you cut your hand, the hand sends impulses to the brain, the brain sends back, and your feel pain in your hand.
    Here is a clear connection between brain and hand, the impulses. The brain knows what the hand is feeling (anology to "knowing when the hand has to evolve).

    But what is the connection between the lung that must evolve and the DNA ?

    I know mutations happen daily, uv-light changes our DNA a little bit,
    when a new child is born (the father/mother cannot duplicate his/her 23 Chromosomes perfectly without any errors, the newborn is always little bit "different"),
    or when our cells repair, its always with some errors.
    But where is connection to adaption (the gills need to become lungs coz it is beneficial) ?
    I dont think spontaneous DNA-errors really lead to a "perfect" lung, all the animals and we are "too adapted", i think there is something like a plan (like the "impulses" telling the DNA what needs to be evolved).

    Or is there no connection between the lung and the DNA ("impulses" telling ...) ?
    Is the whole process of changing/evolving the lung based on these spontaneous genetic errors (uv-light, error during duplication,a gill-fish born with a lung giving it to all other) ?
    I kinda believe there is something telling the DNA how to mutate.

    I know a fish/amphibia born with a pseudo-lung, which is not useful in water but on land, can give this ability to the new generation, and if it is benecial the whole population will be "infected", and settle land coz they survive there better than in water (coz they have lungs now).
    And i know many other scenarios why they would evolve. But this is not what the question is about.

    This scenario is unplausible to me (i took a simple scenario):
    generation 1: one fish born with pseudo-lung. The fish infects all within the population.
    Gen. 1000: another fish born with a better pseudo-lung. Infects all.
    Gen. 100000: another fish born with an even-better lung, infects all. Now the fishes can stay longer alfresco.
    Gen. 1mio: another fish born wth fully formed lung, infects all, now all fishes have a better chance to survive on land, "lets live on land".
    Every fish has the code to build a lung in them and give it to next generation, they give to next etc. and they have the code in them and are born with lungs.

    Are all mutations working like that, or is there something that "tells" the DNA somehow what, when and how to evolve the lung, or make the lung "better and better" (to fit in a new environment with another sort of atmosphere, pressure, oxygen-amount etc.) ?

    Are these spontaneous mutations, every fish-individuum after some time has, leading to success just because the natural selection picks them every time ?
    That mean theres no requirement for an impulse/connection between lung and DNA ?
     
    Last edited by a moderator: Apr 24, 2017
  8. Jan 28, 2010 #7

    HallsofIvy

    User Avatar
    Science Advisor

    Re: Welcome to PF!

    That is exactly what everyone has already been telling you- nothing tells DNA to evolve. DNA is changing all the time. If an animal has moved into an environment in which a lung is more useful than gills, whether or not, and when, its descendents develop lungs rather than gills is purely a matter of chance. If the change does not occur, it may well happen that the species dies out.

    You seem to be trying to believe in some kind of "directed evolution" rather than Darwinian evolution. The evidence is all the other way- there is no "arrow" to evolution, it is all "local" in time.

    No, a being cannot "infect" others of its population, only its own offspring.

     
  9. Jan 28, 2010 #8
    I think what's needed to be done here is that questiner needs to go and do some research on evolution and on evolution of specific species. For some reason you are under the impression that before land animals ALL animals in the water were fish and ALL these fish were the same type of fish as we have now. This simply is NOT true, just look at our oceans now days and you can see it still is far from the truth. A dolphin lives in the ocean but it's far from a fish.

    Here is some information on various stages in animal evolution throughout history:

    http://sci.waikato.ac.nz/evolution/AnimalEvolution.shtml

    There's also a video I'm pretty sure done by BBC that explains evolution quite nicely but I seem to forget the name I have it downstairs and if I find it I'll post the title. Maybe it's on youtube.

    @ the original question. Something to look up would be evolutionary pressure. It is possible to exert pressures on to a species so that it KEEPS certain mutations, however the DNA is mutating all the time, normally these mutations are harmful or neutral.
     
    Last edited by a moderator: Apr 24, 2017
  10. Jan 28, 2010 #9
    Evolution is like poker. Say you have a huge table full of poker players. Everyone at that table wants to make it to the next table, which is the next round of the poker tournament. Everyone gets dealt a hand. Some people get good hands, some people get bad hands. The people who get bad hands are the ones who lose and leave the table, so you're only left with the people with good hands. After looking at all the players who made it to the next table, you see that they had flushes, straight flushes and really good hands like that. It seems like something directed them to get those hands, since you've played poker before and realize there's no way they would all get great hands like that. But what you didn't see was all those people who had bad hands who left the first table long before you showed up.
     
  11. Jan 28, 2010 #10
    Often it is not so much a difference in the genes themselves, but in how they are expressed during development that causes evolution. That is how some species can be so similar genetically, yet so different physiologically. It's all in the epigenetics...

    There seem to be some mechanisms in place that conserve successful genes (or genes critical to survival) and allow mutations to accumulate in not so successful genes. Sometimes these genes are also duplicated and while one copy is conserved, the other is allowed to accumulate mutations. It is possible that these genes that are mutated could become more successful than their predecessor (by chance), in which case they then become the conserved copy.
     
  12. Jan 28, 2010 #11
    This is exactly it.

    If we use leroys example of playing poker, which was ok but I'm going to switch it up a bit to include evolutionary pressures.

    Imagine you were playing this poker game and you decide to play quite tight. However it's not working out for you, you're not losing a lot of chips but you're not winning any either because of how the other players are playing (let's assume they all play tight as well). So now you decide to change it up a bit, get more aggressive start making bolder bets etc. and you're chip stack now starts to grow.

    In this situation you began as a tight player and evolve to become a looser more aggressive player after you've seen how the rest of the table was playing. However being a loose aggressive player from the very beginning MAY have been detrimental to how much you won or it wouldn't have made much of a difference. However as the game proggressed the pressure on you to win more chips caused you to change up your style to do exactly that, even though at the beginning of the game it wouldn't have been exactly the best idea(in your mind).

    This isn't a PERFECT analogy but I think it works, at least I can understand it. :tongue:
     
  13. Jan 28, 2010 #12
    Re: Welcome to PF!

    No. I know Evolution is random (aka leroysjenkens poker example). I just thought the accidents (like a fish surprisingly born with a lung) are not enough.
    So i asked if DNA knows what/when/how to evolve. You know, some kind of mechanism that helps the natural selection to "vote" the right mutation and let it spread within the population.

    Now i know there is no "impulse" or something like that, it is just accidents that might turn out to be beneficial to the population.


    I never claimed. I meant what you have in mind. The individuum gives the mutation to its offsprings, then it dies, the offsprings find some mates in the population, "infect" them, they mate further and infect other untill the whole population is infected.
    I just shortened my explanation.



    @ zomgwtf

    "For some reason you are under the impression that before land animals ALL animals in the water were fish and ALL these fish were the same type of fish as we have now. This simply is NOT true, just look at our oceans now days and you can see it still is far from the truth. A dolphin lives in the ocean but it's far from a fish."


    What made you believe i think all fishes are the "same" ? Because i implied all fishes have gills ?
    I know not all fishes have gills, lungfishes existed 400 millions years ago, obviously they evolved lungs long before some other fishes (who actually already evolved in the water into amphibia-like life forms before they entered land) adapted to land-life 380-360 mio ago.

    Some fish dies out (like Placodermi), some stay fish-like, some change shape and may become land-animals or something elase. Some fish dies, other become a new species and enter their niches. When did i say "ALL these fish were the same type of fish as we have now" ?

    Believe me, i know the history and the origin of a lot of species and taxons or organs like the lung. The only thing i asked is, is there some kind of mechanism that makes the DNA know what to evolve.


    @ BoomBoom

    "There seem to be some mechanisms in place that conserve successful genes (or genes critical to survival) and allow mutations to accumulate in not so successful genes. Sometimes these genes are also duplicated and while one copy is conserved, the other is allowed to accumulate mutations. It is possible that these genes that are mutated could become more successful than their predecessor (by chance), in which case they then become the conserved copy."

    This kind of thing is what i was searching for.
    Something that helps the natural selection to vote the "right" mutation.
     
  14. Jan 29, 2010 #13
    Last edited by a moderator: Apr 24, 2017
  15. Jan 31, 2010 #14
    Re: Welcome to PF!

    thanks for link, little bit difficult but interesting.




    Now i understand how it works, the mating "votes" the mutation.
    As long it is given to the next generation and the fallowing ones, it lives further.
    But, if the population is not succesful and dies out, the mutation dies with them.

    Last question:
    Is Evolution always starting like that ?
    A gill-fish born with a lung or something other than a gill,
    or one bacterium with a light-sensitive skin that becomes an eye (1000 - million years later).
    Is it always ONE individuum born with some "anomaly" that evolution starts with?
     
    Last edited by a moderator: Apr 24, 2017
  16. Jan 31, 2010 #15

    russ_watters

    User Avatar

    Staff: Mentor

    How does water know it is supposed to flow downhill instead of uphill?
     
  17. Jan 31, 2010 #16

    tiny-tim

    User Avatar
    Science Advisor
    Homework Helper

    Water which has mutated to flow uphill either turns into ice or snow, and is unable to breed, or escapes the Earth completely. :smile:
     
  18. Feb 1, 2010 #17
    Re: Welcome to PF!

    Questiner. I know what you are getting at. You think there must be some inherent abiility for the body to communicate to the genes that "a new lung or less hair" etc is needed for the species to survive the ambient conditions. The fact that plants can adapt to their environment, or what is going on around them seems to confirm this communication or knowledge you speak of, cos they can do it so much quicker I believe.

    There is a plant on one of the islands in the Pacific (I think) and over the course of 20 years (an incredibly short timescales) it has changed where it locates its seed in order that the birds can get at them (cant remember the precise details). its like the plant "could see, or knew" what it needed to do and the botanists were fascinated when they saw it, particularly how quickly it happened. But I reckon the botanist only came across it just at the point of the newly evolved plant becoming the dominant gene group, it was probably building up to it for thousands of years...and cos the birds could get at its seeds easier then it became the dominant one, its not so well designed counterpart died off, and so did the innappropriate gene.

    What you have to get your head around though, is the timescales. They are mind bendingly massive. The human body has been evolving for millions of years, and it took 100 or 200,000 years for the body to adapt from eating a carnivorous diet (blood group O), to that of fruit and veg (blood group A). It took as long again to evolve the B blood group. The newest blood group is AB and is only about 5 thousand years old...The body didnt 'know' it needed to adapt to the changes, its was purely a series of accidents and genetic blunders that brought us to where we are today. Blood group O was/is suited to a mainly meat diet, blood group A is fruit/plants, Blood group B would be wheat and the likes and the newest one AB is adapted to eat pulses etc. If meat were to be totally wiped off the face of the earth..the O group would fade away in time too...cos the all plant diet wouldn't suit it, make the O's susceptible to disease and eventually eliminate them...

    These changes in blood group were as a result of less meat being available, and the onset of horticulture. And...if you find out what your blood group is it might give you an idea as to why you can drink spirits, but not beer...dont particularly like bread or milk.. Me, I could drink gallons of spirits, but ne'er a drop of beer and could never understand it....twasnt til I read about the relationship between blood group and diet.


    The timescales are huge huge huge, and the above might be wrong, its decades since I read this stuff and for some reason I've got 20,000 years in my head, so wide open to correction.

    Evolution can be likened to the flat earth theory, its only when you stand well back and look at it with a wider vision that you can really grasp its size and shape, cos when your shanks mare (feet) are attached to the ground, you are too close to see it in its entirety..
     
  19. Feb 1, 2010 #18
    Re: Welcome to PF!

    Not necessarily, it could be all offspring from a certain mated pair that produce the 'anomaly'...depends on what the 'anomaly' is.
     
  20. Feb 2, 2010 #19
    Re: Welcome to PF!

    Who knows if DNA (or the genes in it, or a mechanism or something) can "see".
    There could be something that favors one mutation over another mutation, kinda pick n choose, but who knows. It needs more research.

    Didnt know that about our blood groups, thanks. I hope you remember it right. Gotta research it to know for sure.
    But it makes sense that AB is the newest, its very rare (5% of all ppl) and it is compatible with all groups.


    Not always huge. Skeletons from 5000-6000 years ago were tested ... looks like they couldnt drink milk (Lactose intolerance). Now Europeans can. I say went quick.




    Oh yeah thats the other variant i hadnt in mind.
     
  21. Feb 2, 2010 #20
    DNA doesn't 'favour' anything, sure more research needs to be done into DNA and mutations but it's beyond any doubt that DNA can 'see' and 'favour' a particular mutation. What causes mutations to be able to occur quicker in some species (suchas viral) is the lack of correction machinisms. In humans when a copy of DNA has an error it is fixed by various other parts of the body to reduce the impact of mutations. (since mutations are mostly negative or neutral impacting this is good.) For some species however the ability to continually adapt is much more needed so they have limited machinisms for correction.

    What causes evolution isn't DNA mutations ... it's natural selection.

    And the reason I figured you thought that all fish in the ocean back then were all the same 'sorta fish' was because you assume that everything in the ocean used gills to breath and suddenly 'a lung came'... which is far from what actually occured.
     
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook