Help! questions regarding evolution from a layman.

Discussion in 'Science & Society' started by semberardens, Aug 11, 2012.

  1. semberardens Registered Member

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    Hello

    I have a few questions regarding evolution.

    1- if short stature equals better heat retention why are people from Europe (Russia for example) usually taller statistically.

    2- why haven't native Americans developed white skin since the also lived in colder climates.

    3- and this is the one I struggle with the most and it's probably because I'm misunderstanding something, evolution is a very slow process that takes thousands and millions of years, shouldn't then the first advantageous mutation be so small therefore rendering it not advantageous at all?, one example that comes to my mind is webbed feet, I mean wouldn't its earliest form be so small therefore making it negligible.

    please don't kill me.
     
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  3. spidergoat Liddle' Dick Tater Valued Senior Member

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    1. Furs and warfare.
    2. It's almost white, perhaps there wasn't enough of an advantage (or time) to lose that last little bit of melanin.
    3. Evolutionary changes can happen as long as there is a gradient of advantage. A small advantage is still an advantage.
     
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  5. FTLinmedium Registered Senior Member

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    Regarding #2, what spidergoat said, but also I believe it is more overcast climates that are the problem, rather than cold ones. Europe is cloudy and warm. There was also probably sexual selection involved (e.g. the skin may have gotten whiter than it needed to be for cultural reasons), and a little genetic drift.
     
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  7. defekkto The Mexi-Canadian Registered Member

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    I think culture plays a significant role in human evolution, like the tallness factor. People all over the world are getting taller, why? Tallness is something women often look for in men. Also we are growing to our full potential, something that didn't happen often in previous centuries because kids didn't always receive the nutrition they needed. I think the skin color is also very culturally defined.
     
  8. Yazata Valued Senior Member

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    5,579
    It might not be a matter of stature so much as it's a matter of body proportions. Whites sometimes appear to me to have shorter arms and legs, relative to the size of their body, then do some of the tropical African peoples. Surface area to volume ratio. You can see it in the Olympic track-and-field races and on basketball teams.

    They do have relatively light skins, when compared to sub-Saharan Africans, Dravidians and Melanesians.

    Natural selection selects among heritable genetic variants on the genomic level. And these genes might control something like fetal development. So even a small molecular difference in a single gene might have a dramatic effect in how a body subsequently develops. That's one reason why fairly large deviations from parental-type can appear quite suddenly.

    Imagine that a small mutation in a single gene changes something about how hands and feet develop. That might result in your webbed-feet appearing all at once. I guess that typically, that kind of change would be a serious disadvantage. But it might be advantageous for an organism that spends a lot of time in the water, so the new variants might just might turn out to have a selective advantage in that ecological niche.

    In other words, evolution probably isn't always a matter of tiny imperceptible differences building up over time. It can happen in a much more jerky fashion, with quick changes interspersed with periods of little apparent change.

    It needn't always be slow either. Evolution can happen on the scale of mere decades. We see that happening at the present time as new drug-resistant forms of disease microorganisms continue to appear around the world.

    No reason to do that. Your questions show that you're thinking. That's a very good thing.
     
  9. semberardens Registered Member

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    1- but didn't Neanderthals have those things as well ?, plus this is the first time I have heard that warfare is what led to the European's being taller can you give me a reference to this.

    3- I'm sorry I still don't understand , it still seems to me that a very small advantage would be negligible.


    Yazata

    (It might not be a matter of stature so much as it's a matter of body proportions. Whites sometimes appear to me to have shorter arms and legs, relative to the size of their body, then do some of the tropical African peoples. Surface area to volume ratio. You can see it in the Olympic track-and-field races and on basketball teams.)

    That might be the case, but I have seen a test on this BBC documentary ( http://www.youtube.com/watch?v=7p-ost_rRtM) where they see the heat retention between two Europeans, one of them has a body somewhat resembling that of a Neanderthal and the other does not, the former preformed much better than the latter, the scene starts at about 15 minutes.

    (Imagine that a small mutation in a single gene changes something about how hands and feet develop. That might result in your webbed-feet appearing all at once. I guess that typically, that kind of change would be a serious disadvantage. But it might be advantageous for an organism that spends a lot of time in the water, so the new variants might just might turn out to have a selective advantage in that ecological niche.
    In other words, evolution probably isn't always a matter of tiny imperceptible differences building up over time. It can happen in a much more jerky fashion, with quick changes interspersed with periods of little apparent change.)

    But wouldn't the odds of that happening be improbable, I mean I have heard Steven Pinker saying that the odds of a single mutation leading to human behavioural modernity to be astronomical, wouldn't this be also be the same?

    (It needn't always be slow either. Evolution can happen on the scale of mere decades. We see that happening at the present time as new drug-resistant forms of disease microorganisms continue to appear around the world. )

    But does that also translate to more complex animals?.

    thanks for your patience .
     
  10. semberardens Registered Member

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    I think that's not exactly true because early Cro-Magnon people as well Homo Heidelbergensis were as tall if not taller than humans today, humans became shorter after farming which did not provide for them as much as hunter gatherer life style, on the matter of sexual selection I don't know enough but would sexual selection go against a survival advantage?.
     
  11. Aqueous Id flat Earth skeptic Valued Senior Member

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    6,152
    semberardens,

    I think you would have to try to analyze what "survival advantage" means, both pre- and post-civilization, to get close to the answers you seek.

    Sexual selection simply means that men and/or women tended to choose each other due to a some subjective attraction. If the population as a whole, over many generations, practiced a trend in choosing mates, then particular traits would effectively be selected. Who knows. Did ancient Nordic people marry tall sons and daughters for the same reason they bred certain animals - for the purpose of creating a warrior stock? It's entirely speculative, but a possible explanation.

    It's not clear to me what stature has to do with survival advantage overall. Is it heat radiation/retention? Is it being able to reach higher-hanging fruit? (For what?) As spidergoat mentioned, wars would tend to select for height, and, as far as heat retention, the use of furs. The main disadvantage that comes to my mind is the demand for slightly better diet to support a larger body. But how would we be able to figure out trends in nutrition? Perhaps people ate better in enclaves where the probability of finding game increases. Developing agriculture and learning to store food for the winter would seem to have a huge impact, but this becomes more problematic in poor soil and climate. Perhaps the struggles there produced more wars?

    A similar analysis can be applied to your question of why dark complected people moving to a colder climate may have retained their melanin. You may want to refresh yourself on the relationship between Vitamin D production vs. skin cancer. The earliest Americans crossing the Bering land bridge invariably had a diet rich in fish, which is one of the few nutritional sources of vitamin D. This would mean that the darker skin, masking UV and reducing photosynthetic vitamin D production, was compensated by the diet, so there was no selection for fairer skin because the survival advantage one way or the other was zeroed out. I suspect that river fishing remained a staple for early Americans, but this gets back to pure speculation.

    You may also want to explore the the evolutionary causes of sickle cell anemia. I think it will help you understand how a new trait can emerge despite the "modern" interventions like war, furs, communal living and so on.

    One more thing: an example of how sexual selection would go against survival advantage is this. Consider the genetic aberrations of inbreeding. They highly disadvantageous: mitral valve prolapse and blindness are two that come to mind.
     
  12. semberardens Registered Member

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    I know what sexual selection means but I think it's too much of a simple answer, I'v already said that Neanderthals wore fur and most likely went to war with each other , heat retention is clear advantage otherwise you wouldn't have the Neanderthals evolving to their body type and like I said they were living under same circumstance with regards to usage of fur and experiencing warfare. also why is this sexual selection unique to Europe.

    regarding the colour of the native Americans I think you might be true , although people living in Nordic areas like Norway have a fish diet , and presumably white skin
    developed as recently as 6000, its very possible that the Norwegian way of life was much older than 6000 years.

    I think inbreeding might have had a survival advantage actually, in areas with scarce resources , group unity and cohesion under a tribe is very important and the way you do that is by marrying with each other and not marrying outside the tripe
     
  13. Aqueous Id flat Earth skeptic Valued Senior Member

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    By inbreeding I was referring to very narrow family boundaries, which are known to produce congenital anomalies. Nature has already "forced" humans to breed across family lines, through some mechanism worked out long ago.

    I don't think it's the light complexion that needs foods like fish, since the reduction of melanin allows for Vitamin D production with shallower angles of sunlight. It would be the people already adapted to high sunlight (tropics and high altitudes) who move to a region of less sunlight. The question was: what would be the survival disadvantage for them? My thinking is that their elevated melanin reduces their ability to produce Vitamin D from the shallow-angled light. These folks would presumably compensate by eating Vitamin D-rich foods like fish. That would stop the selection process, and it would account for dark-skinned people where sunlight is scarce. People such as the Inuit come to mind, who cannot expose their skin to the elements for many months, who rely on seafood, and who still carry the trait for melanin.

    I'm not sure if I understood your remarks about Neanderthals. If you're asking why they evolved a different skeletal structure than us, I would think that would involve a lot of speculation. Heat retention is a commonly mentioned, but it's unclear when either they or we began using hides and building fires to survive cold seasons. There would also be local climate shifts to factor into that analysis. I would think that if and when there is ever an answer to the question of their extinction, it may be possible to move beyond the point of sheer speculation into something a little more tangible.

    I'm also not sure to what degree I've oversimplified sexual selection. In the wild we see how males attract females. This process of sexual selection was highly evolved before humans appeared on the scene. My intent was to introduce how cultural influences could alter the natural process of sexual selection. An example would be arranged marriages, or however this may have taken place in prehistory. Such a cultural phenomenon would alter the natural form of sexual selection. I can't speak for women, but the allure of large hips (better birthing), large breasts (better lactation), etc., would seem to be universal in modern times, as if this was a hard-wired selection acquired from prehistory, when sexual selection would have been more influential on the passage of traits.
     
  14. semberardens Registered Member

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    The question regarding the Neanderthals is why didn't we evolve similarly to them(since heat retention is clearly advantageous and I have given above a link to this), and I have also replied to the fur and warfare argument.(Neanderthals had those things as well from what we know)
     
  15. defekkto The Mexi-Canadian Registered Member

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    I think the reason we didn't evolve similarly to Neanderthals is because they actually went extinct, and although they are considered one of our evolutionary forefathers, the Cro-Magnon co-existed with the Neanderthals for some time and eventually took over. Cro-Magnons were from a different branch of our evolutionary family tree, so it wasn't like we came directly from Neanderthals. For whatever reason the Cro-Magnons survived and flourished while the Neanderthals became extinct, so we evolved from them. I don't think warfare has anything to do with the height conundrum, because Neanderthals were pretty tough bastards, they seemed to be made for battle. Heat retention could have something to do with it, since our direct forefathers the Cro-Magnons came from Eastern Africa.
     
  16. Cavalier Knight of the Opinion Registered Senior Member

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    You are thinking of it slightly incorrectly. Imagine you inherit a mutated gene that is beneficial. What that means is not really that you are more likely to survive while everyone else dies around you, but rather that your reproductive success rate has risen. So imagine that the average person in your population expects to have 3.00 children that survive to adulthood. Because of your beneficial mutant gene you, and anyone with your gene, can expect (on average) to have 3.01 kids that survive. That is a minuscule difference to you, but imagine that you have only two kids with that gene (below your average). Now you have two people with that subtle advantage.

    Now imagine your progeny, over the next 1,000 generations. In every generation, on average, you can expect the number of people who have your special gene will grow, and, better, they will become a larger and larger proportion of the overall population over time. Give it long enough, and people with that mutation will come to be the majority.
     
  17. semberardens Registered Member

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    I understand what your saying , but what I am saying is basicaly if this process takes so long and is so gradual then wouldn't there be ---practically speaking ---- no difference between the first animal inheriting the advantageous mutation and the rest of population ?.

    Especially if we are not talking about simply being bigger or stronger but maybe more complex changes and I gave the example of webbed feet.
     
  18. Aqueous Id flat Earth skeptic Valued Senior Member

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    6,152
    How they lived probably has nothing to do with how or why they evolved. I think you would want to try to figure out how Homo antecessor lived (the postulated common ancestor), and then to try to look for why H. neanderthalensis and H. sapiens diverged from them. There is the possibility that H. antecessor were cannibals, and that speech may have evolved at around this time (perhaps 1.2 MYA). It may have taken until around 600 kYA before the Neanderthal divergence was complete. The question you are asking is why. I'm not sure anyone can answer this question unless some relevant evidence comes along. Obviously we can all speculate. I'd have to say your guess is as good as mine. What if H. antecessor turned out to be barrel chested, and H. sapiens represents the divergence from the main clade?
     
  19. Captain Kremmen All aboard, me Hearties! Valued Senior Member

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    A more apposite question is why our Northern peoples' skins have become so pale?
    We all came out of Africa, so our ancestors had black skin.

    I have suffered all my life from over-whiteness.
    I never get a sun tan.
    My skin goes from white to burnt white, which is a sort of crimson red, after that a peely white and from thence a freckly white.
    I'm too damn white!

    Even with their darker than Caucasian skin, American Indians suffer quite a lot of sunburn, and are recommended to wear sun screen creams.
    They are too white too.

    Please Register or Log in to view the hidden image!



    From http://www.skincancer.org/prevention/skin-cancer-and-skin-of-color

    I can only assume that there is some cultural preference for white skin
    which overrides the danger of dying from skin cancer.

    If it was part of our inbred sexual preferences , then Africans should also be whiter.
     
    Last edited: Aug 13, 2012
  20. semberardens Registered Member

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    I don't think your understanding my question and it's my fault, I'l try to be clearer here.

    Neanderthals arrived in Europe thousands of years before homo sapiens and adopted to the climate well through their body structure .(http://www.youtube.com/watch?v=7p-ost_rRtMat 15:00) My question is after arriving to Europe thousands of years after the Neanderthals why didn't Homo sapiens adopt a similar body structure since it was clearly advantageous .

    Anyway the question I'd really like somebody to answer is the third question, its the one puzzling me the most.
     
  21. Cavalier Knight of the Opinion Registered Senior Member

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    Again, you have a narrow reproductive advantage (and that advantage is the only one that matters...though note that being bigger and stronger may allow you to reproduce more offspring than the average). So the odds are that you and anyone inheriting that trait will have slightly more offspring than the average...but any one INDIVIDUAL could really have less than the average, because there will be a variance in the actual number produced from the expected mean (especially if the expectation is that you will have 3.01 children).

    So long as you have offspring at all, and pass that mutation on, the odds remain good that you or your offspring will have as many ore more offspring than the average, and if you can have multiple offspring with the new genetic info, then the likelihood of that gene surviving only increases over time.

    It is possible that genetic advantage will be wiped out. It is possible that you will have no offspring and the new advantage will die with you, but if those with your gene are having 3.01 kids on average and the rest of the population is having just 3.00 kids, and both sets of genes survive, the odds are good that over time your genetic variant will come to be the majority, because the population grows geometrically, but your line will grow at slightly faster rate.

    Think of it this way: Imagine two populations, one has a birth rate per person of 3.00 and the other of 3.01 in each generation. The first population will quadruple in size every 1.2619 generations. The second will quadruple every 1.2580 generations. It doesn't matter if the first starts with 100,000 individuals and the second has just 10, over time there will grow to be more of the second group than the first, barring some accident that happens to wipe out the second group.

    Using those numbers it might take 3,000 generations for the new population to be larger than the old one, but there's a good chance it will occur.
     
  22. gmilam Valued Senior Member

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    Here's my take on #3 - as another layman...

    Mutations that are not harmful are more than likely neutral until a change in the environment comes along. At that point it may remain neutral, it may become a disadvantage... or it may become an advantage. It's really just the luck of the draw. The rocks are full of fossils from extinct species that flouished for millenia.
     
  23. semberardens Registered Member

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    Cavalier


    Your saying that if I inherit a beneficial mutation, the odds are that I will have more offspring, and slowly my offspring carrying the advantageous mutation will become the majority population and then eventually all the population will be carrying the mutation.

    I understood you completely FROM YOUR FIRST REPLY, I don't think you understand my question. Again, if evolution is a very slow and gradual process, wouldn't there be PRACTICALLY speaking, no difference between the first mutated animal and the rest, meaning he wouldn't be able to even produce more offspring?.
     

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