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

Mutation and evolution

  1. Apr 1, 2006 #1
    Hello all,

    First I'd like to say that I'm not a great scientists nor a great thinker. All I do is try to derive a common logic.

    A few days ago, I had a lesson on "how do mutations affect us." And so I copied all the definitions into my notebook. One of them was 'Germ-line mutation" and "Somatic mutation." My teacher asked, "which one do you think is the worse one?" It's logical that the first one, because mutations aren't any good, as far as I observed and Think and so if something bad happens to you, it's better that it doesn't pass to the next person. Then I thought about evolution right away.
    Those monkeys "millions of years ago..." :rolleyes: had to have many frequent good mutations to evolve into us and if so, some of them should be visible in today's monkeys. Or even we should see frequent good mutations of humans, but yet we do not. Why is it? And what's wrong with my thinking?

  2. jcsd
  3. Apr 1, 2006 #2
    You don't see the bad mutations (in the animal world) as often because those offspring don't make it long enough to reproduce whereas virusus mutate and as a result it is harder for us to fight them off.
  4. Apr 1, 2006 #3


    User Avatar

    Staff: Mentor

    A million years is a long time and we aren't all that different from chimps, so no, we should not be seeing evolution on human lifetime timescale.
  5. Apr 2, 2006 #4


    User Avatar
    Staff Emeritus
    Science Advisor
    Gold Member

    We do see good mutations in humans, a mutation in hemoglobin causes it to become crescent and the red blood cells sickle shaped (sickle cell anemia). In normal conditions this is deleterious to the health of an individual, in regions infested by the malaria parasite is actually good for you: the parasite cannot infect (or at least with a lesser rate) the red blood cells and so you are resistant to malaria. Sickle cell anemia has a higher incidence in regions where malaria occurs: natural selection.

    This is just one example, there must be others. The reason we don't see frequent good mutations, is that they 1) mutations are repaired by the cellular machinery 2) a mutation is more likely to occur in a region that is not a gene 3) the mutation then is more likely to be deleterious.
  6. Apr 2, 2006 #5
    Yeah I believe only the single recessive gene version is beneficial in sickle cell, the double recessive gene version leads to anaemia and greater risk of premature death.

    Mutation is self evidently benificial, it may produce some pretty harmful disease, but it also is a way to overcome some pretty harmful diseases. Without mutation and it's genetic "quantum leaps", evolution would be far slower. As was mentioned viruses constantly outpace true life because life cannot mutate as quickly. Thus there evolutionary viability is increased by a factor compared relatively to their division rate(or their ability to mutate: a mutation factor) In evolution a vacuum is abhorent(i.e anything that is non beneficial, or even detrimental is weeded out of the selction process) Thus if you see a factor that exists in nature it's there because it promotes evolution, simply look at the reasons why it might do so and you answer your own question.

    EDIT: there is also some controversial ideas that human life is not evolving at all any more due to us contolling the environment instead of it controlling us. But I tend to think evolution is happening upstairs, even if it is only scientific evolution :smile: What selection factors are their if everyone weak, strong sutpid or intelligent gets the chance to breed? What traits or mutations are selectively bred out of our population I wonder? Is having ginger heair an advantage? Seeing as it means higher risk of skin cancer and less tolerance to pain(aparently) Lots of things in the human gene pool that no longer obey the evolutionary rules, or a obey a slightly modified set.
    Last edited: Apr 3, 2006
  7. Apr 2, 2006 #6
    Well, for one thing, a good mutation may be recessive or only partially dominant. So let's say someone has one - in their germline - and pass it on to their kids. If it's recessive, you wouldn't know that it's there. And we don't have sibs mating very often, or cousins, or second cousins..... so you might never see it as a homozygous condition.

    Also, our species hasn't gone through any serious bottlenecks in the recent past, and those seem to be necessary to see the sorts of changes in morphology that you seem to be thinking of. It's hard to get geographically isolated populations of people anymore, too.
  8. Apr 3, 2006 #7
    Do you know any other good mutation except for that one?

    If it all is so, then in fact we should see a lot of good mutation right now.
    The Earth is believed to have 4.5 billion years. Suppose it does. The life started to form on Earth about 2 billion years ago. Between all the organisms in the world (us, animals, bacterias) there is about 2 million differences (maybe even more). Then if we divide 2000 million by 2 ml we get 1 good mutation each 1000th year. And in fact, good mutation are not that common, suppose 25% of all mutations then we get one good mutation each 250 year + recessiveness. I maybe wrong with my calculations so let's say each good mutation 250 year, everyone going at random. People started to observe and note animals and plants about 2000 years ago, so there is very low probability that none of them has ever noted a single visible good mutation in organisms. What am I thinking wrong now? :)

  9. Apr 3, 2006 #8


    User Avatar
    Staff Emeritus
    Science Advisor
    Gold Member

    http://www.pbs.org/wnet/secrets/case_plague/clues.html [Broken]

    more quick reading...

    Note that most mutations are neutral. Then the environment/ecosystem changes and a previous neutral trait becomes more significant.

    It's not "believed"...it's well proven.

    nitpick...more like 3.8 billion years ago.

    It's a common misconception that evolution = progress. That is not so. Evolution = change. Mutations are a source of variation in a population. Some variations do better than others and tend to propogate. As I noted above, many mutations are neutral at first (and thus, can continue to spread aside from natural selection) until some shift in the ecosystem makes the feature more useful (and thus that part of the population tends to out-compete other parts). With enough separation in the gene pool, you get a new species. It's not that each mutation is a beneficial step to a fixed, better form. There's no end-goal in evolution that mutations work towards. There is change and then there is selection. You are assuming that there must be progress for speciation to occur.

    Consider all the varieties of humans. There are all kinds of variations in our gene pool attributable to mutations. As the world changes, some people may do better than others (e.g., disease resistance, temperature tolerance, diet tolerance, etc.)

    Human evolution might be viewed as progressive in terms of relative intelligence or brain size, but it could also be viewed in terms of losses (e.g., lesser ability to climb trees, or lesser muscle strength, etc.).
    Last edited by a moderator: May 2, 2017
  10. Apr 3, 2006 #9
    Last edited by a moderator: May 2, 2017
  11. Apr 4, 2006 #10


    User Avatar
    Staff Emeritus
    Science Advisor
    Gold Member

    There have been several bottlenecks (plague, famines) and there are isolated populations (those isolated by their geographical location, their religion, or social boundaries). Everyone is jumping onto these populations to study their genetics, but since these populations haven't been isolated for very large time spans the effects will be subtle.
  12. Apr 4, 2006 #11


    User Avatar
    Staff Emeritus
    Science Advisor
    Gold Member

    Hi heartless

    The immune system is a good example because it changes so quickly (something that is easier to see directly). For what it's worth, DNA changes can be a big part of disease resistances and much like the predator-prey relationships, the pathogen-host conflicts have also been a big driving force in evolution. Anyway, you're asking about larger scale changes. First, it's important to realize that most large scale changes (when viewed in retrospect) require multiple small scale mutations. A beneficial macro-mutation is rare (more rare than a beneficial micro-mutation). Wings are not expected to form in 1 generation. Rather, there is a slow shift in anatomy, with each step providing some benefit or neutral trait (important point there), which eventually leads to what can be called a wing. For example, gliding might be an intermediate step before powered flight. If you define evolution to mean huge, quick steps, then most people would agree that does not happen.

    Note that some macro-mutations can happen. Most are birth defects that are harmful.

    One understandable example is when there is something like a gene duplication or a change in the genes that time body development. Simplifying...if a gene that says "make 1 of body part X" is duplicated, then you may get 2 of those parts. Or if a gene says "grow this feature for X amount of time" is changed, it may grow that feature for twice the time. Etc. I seem to recall reading about an example of a segmented insect (e.g., centipede) that can gain an extra segment with a developmental gene change. Is that extra segment & pair of legs beneficial? Depends on the circumstances.

    There have been many changes, but I was talking more generally about local changes which can include many faster-acting factors than just long-term climate effects...e.g., new predator/competitor moves into the area, reduction of a particular food source, new disease affecting the population, etc.

    There are many cross-checks on those kinds of calculations and they are careful to report uncertainties (e.g., they'll report an age at X years +/- some percentage). I'll see if I can provide some helpful links on that. To be sure, they're aware of the changes through time when they do these kinds of studies.

    A duplicated/transposed/relocated/etc. gene is new information even if it's a variation on something pre-existing. If your DNA says "A" and then it changes to "AA", that is new & different. With 26 letters in our alphabet, we can arrange them into countless variations of information. DNA has 4 letters in its alphabet to work with (A,G,T,C).

    Well, yes, a little. But most of that small-scale change falls under immune system changes and racial statistics. Larger changes for humans occur over longer timeframes (we are different than humans from 20,000* years ago, even more different than humans from 200,000** years ago, and very different than our ancestors from 2,000,000*** years ago).

    * e.g., H. floresiensis, H. neandertalensis (30-40,000 years ago)
    ** e.g., H. erectus, archaic H. sapiens
    ***e.g., H. habilis, A. africanus
  13. Apr 4, 2006 #12

    I'm sorry for this conversation but I really stopped believing words of theoretical physicists, pale-(something) and evolutionits when I realized that they're just doing educated guesses. Like for example take Stephen Hawkin under attention. He spent half of his life working on black holes and after all nobody has ever seen a black hole. Well, many people believe that they see black holes, they it's all just black space. It took him many good hours working out the theory on black holes but the truth is that we don't even know the real properties of black holes. For example, Einstain's relativity predicts (notice predicts) that time stops at the horizont of a black hole but we have no idea what the black holes really are.

    Look at another example, two scientists are taking a tour over African Safari, far away they see two little points moving with some speed. They take the paper, calculate the speed of motion of these two points, and they come up with a solution. Point 1 moves with a speed of about 65km/h and point 2 which tends to move behind the point 1 moves with a speed of about 80km/h. Scientitsts draw a quick conclusion - A cheetah is chasing a gazelle. Suddenly they notice that the first point speeds almost two times faster than a while ago. They take again the paper and come up with a speed of about 110km/h. A theoretical physicists or evolutionists would say "Amazing, a gazelle speeding up 110km/h, that will make a headline. Calculations don't lie." Then they actually come back, and paste some fake pictures in the newspaper of cheetah and the gazelle with a headline "Gazelle the fastest...."

    A real scientitsts would say "It's impossible, we have to come closer and see" They try to come closer, and what they see? Two cars having fun in the middle of nowhere. It's rather odd example but with similar principles which govern these two lets say, different groups of scientitsts. First group trusts only calculations and have a desire to impress people. Second group doesn't believe unless they SEE! Therefore you can't always trust calculations, but as far as possible see it, feel it, sense it.

    Let me put it in other words. A totally new gene that others don't yet possess that grants a person with something, again others don't have. These genes we use now, are already existing in millions of people. No totally new gene was ever noted? Was it? I know I'm changing subjects every time, and I don't know the subject well, but I'm strongly looking for big evidences for evolution, that will let me believe in it.

    How do they know it? They indeed have never seen these people. What if the bones found are of some animals which did extinct years ago and not humans? By the way, how would you feel if evolution isn't true and God made this world indeed about 7000 years ago? (He had to make it anyway, no other explanations exist which won't lead into the creation)

    Thanks for your replies, Good night.
    Last edited: Apr 4, 2006
  14. Apr 4, 2006 #13


    User Avatar

    Staff: Mentor

    Like your statement about radioactivity, that is a horrible, horrible misunderstanding of the science behind black holes. I don't want to hijack the thread, but briefly:

    Hawking (and Penrose) did some calculations based on previous science (General Relativity) that predicted the existence of of objects with a mass so high that light could not escape. These objects were named "black holes" and they do have quite a number of observable properties which were predicted before they were ever observed, not the least of which is an enormous gravitational pull.

    Put quite simply, if you detect the existence of an object via its gravitational pull, but don't see a star there (ie, you see an object orbiting nothing), then you are by definition looking at a black hole.

    But thats only one of many, several different types of evidence for black holes (they also radiate energy via matter falling into them, they also refaract light).

    The logic of your radioactive decay example only works if there is only one radioactive element and it has a long half-life. Then radioactivity would be based on one small set of data points. But, in fact, we have observed hundreds of radioactive isotopes and particles, and all of them obey the same laws. So it is not too much of a stretch to figure that an extremely long half-life isotope will continue to obey the rules of radioactivity.

    And that's even without considering that there are other ways to observe and measure radioactive decay - ie, by the radiation given off.

    So where you said we have only "single evidences", we do, in fact, have thousands of separate sets of "evidences" for radioactivity.
    That's an utterly rediculous story. Science doesn't work that way, and if you simply put real people in that situation and consider how they would act in reality, you'll see that. If you are looking at objects (say, on radar), and you initially conclude that they are animals, then they suddenly start not behaving as animals, any one - scientist or otherwise - would immediately conclude that they are not animals. And that's how the scientific method works: As soon as the new evidence contradicts the old theory or previous conclusion, the old theory or previous conclusion must then be re-evaluated. It would not be logically consistent to theorize via the "pile-on" method - we'd end up with a massive jumble of nothing.
    And they would - so what's your point? You seem to understand that your story is absurd and not how science works, so why did you even say it?
    Wrong. There is only one scientific method and only one scientifically valid way of approaching the acquisition of new knowledge in the natural world. And real scientists understand that your five senses are extremely limited tools for doing that. They also understand that new theories based on calculation alone remain extremely tenataive until such time as observation confirms them. Black holes is a good example of that - the theory had no observational basis whatsoever when first proposed, but many observations were made that exactly match the predictions and hence few physicists, astronomers, etc today seriously dispute the existence of black holes.
    I'm not sure what you mean - you do know that things like radiation create completely new sequences (new mutations), right?

    That's in addition to what was said before - that dna is just a base-4 alphabet and a new sequence can be made just by rearranging a couple of letters. In fact, a similar type of evolution can be seen in language. Sometimes people make typos (even vocal typos) that turn words into strings of letters that are no longer words. Occasionally people decide they like that new string of letters and by consensus, it becomes a word.

    Evolution is actually more like running a computer program, though, and when an error occurs and the program is rerun, you immediately find out if the new sequence will function or cause the program to fail.
    Huh? We have found bones of animals related to humans that aren't humans. We have seen these "people".
    As a Christian, I would be dismayed to learn that we have a God who has gone to great lengths to deceive us into thinking the univers runs according to set laws. As it stands, we have never observed something happen that is utterly incomprehensible by and incompatible with science.

    Put plainly, heartless, your distaste with science is based on the combination of a misunderstanding of it and an unwillingness to learn about how it actuall works.
  15. Apr 5, 2006 #14


    User Avatar
    Staff Emeritus
    Science Advisor
    Gold Member

    Hi heartless,
    As suggested by Russ, I'd also recommend that you read further into how the scientific method works and what the various lines of evidence are for a particular phenomenon you're interested in. If you check a textbook, you'll find a lot of information. If you check a anti-science website, you'll only find strawmen.

    Russ already answered much of your post, so I'll just add a couple more things...

    It's important to understand that a scientific theory is not just an educated guess, but it's a well-tested model that explains the known facts and has broad agreement among the experts in the field. I could further describe what a theory is, but the basic point is that it is deeply founded in experimental/verifiable evidence and has passed tests at trying to prove it wrong.

    Sure, but I'll have to dig around to cite a particular example. Note, like Russ said, a simple point mutation (changing one letter) can create a new gene.

    http://www.talkorigins.org/faqs/homs/specimen.html" [Broken] Those of the genus Homo (H. sapiens, H. erectus, etc.) are considered to be "human".

    Not sure. But I can say that I don't see evolution as anti-God. I think it's possible to have both. However, I do think that some specific religious beliefs are wrong (like a 7000 year old universe), as the evidence is stacked against it.
    Last edited by a moderator: May 2, 2017
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook