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Thread: How did the different human races evolve?

  1. #1
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    How did the different human races evolve?

    Recently I've been curious about why the the different human races evolved to fit their climate, especially as far as the skin pigment is concerned. Does black skin really help well enough for the black people to generally evolve it based on natural selection?
    As in the people with darker skin generally survived and reproduced more while lighter skin people gradually. One fluke person has a bit blacker skin than the rest, and as a result he survives way better?

    This seems to suggest to me that our evolution is not only affected by natural selection, but also by the environment. Somehow the DNA for pigment makes the skin blacker and blacker because of the amount of sun its getting. I haven't heard of any of this, so I'm curious about how it happened.

    While we're on this subject, how long do homo sapiens as we know them date back to?

  2. #2
    I'm just going for a walk... ElectricFetus's Avatar
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    Actual it worked like this: Black people immigrated north, suffer massive Vitamin D deficiency, those with lest melanin (lighter skin) were render healthier and more fertile: so in the end the further north you go the lighter peoples skin. As people move back to southern climates (the Native Americans for example: from Alaska to South America) the reverse becomes effective and darker skin is needed to prevent an overdose of vitamin D and skin burning as well. Today with modern diet and sunscreen vitamin D levels are easily controlled artificially and skin color is redundant. Though with the ozone going out and all it is best to be darker

    The process of evolution being affected by the environment is natural selection!

    Mitochondria DNA puts humans at about 600,000 years old.

  3. #3
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    Well cooked foetus is right! I didnt know about the immigration north but i did know that those people with lighter skin are more likely to develop cancer (probably of the skin) because of the strength of the suns rays in that part of the world. Only the strongest will survive (also the name of a song by Hurricane No.1)

  4. #4
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    Actually cancer risks and skin damage does not have the kind of fatality qualities to kill someone before they breed. Vitamin D though has been linked with fertility and the ability of a women carry a child. Too much are to little vitamin D can have very bad side effects on fetal development and miscarriage rates. People with the appropriate skin color for their latitude had a low miscarriage rate, higher survival rate in childbirth and higher birth weights over those that had inappropriate skin color for that latitude. Unfortunate (or fortunately) modern clothing and diet have ruined and override thousands of years of evolutions skin tone tweaking work.

  5. #5
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    Originally posted by WellCookedFetus
    Actual it worked like this: Black people immigrated north, suffer massive Vitamin D deficiency, those with lest melanin (lighter skin)
    but that doesnt rely answer the question bcos how did those w lest melanin get lest melanin in the first place?

  6. #6
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    Fetus:

    You got it right about skin color. That's the prevailing theory, and while it seems to make sense. Especially since the earlies sapiens found are in Africa.

    On the issue of when sapiens evolved you are way off. Firstly, this is not like physics where you can drop a ball and measure the gravitational force and everyone agrees. There are competing theories out there.

    The dominant theory (called Out of Africa) holds that Homo sapiens (us) evolved in Africa about 150k yrs ago. There are fossils that are sometimes called "archaeic sapiens" that go back farther, but that's really a way of saying we don't quite know where they fit in. mtDNA agrees pretty much with the date of 150k yrs ago. Check out books by Ian Tattersall for a good description of this.

    Some Out of Africa folks would argue that we evolved physically by about 150k yrs ago, but that our unique language and mental ability did not arise until as recently as 50-70k yrs ago (when you start seeing cave paintings and the like). This is a lot harder to prove than just looking at physical features.

    The minority view, called the Multiregional Hypothesis, states that spaiens evolved all over the world at the same time from earlier forms of Homo. That we've basically been one species for the last ~2M yrs. Homo Erectus in Asia, Home Neanderthalenis in Europe, and Homo Ergastor in Africa all were really the same species that interbred and evolved into us. Check out books by Milford Wolpoff on this theory.

    Not sure exactly how things stand right now, but I'd say it's at least 9 out of 10 anthropologist who would subscribe to the Out of Africa theory. Wolpoff doesn't have a lot of support, but he's pretty passionate on his views so I don't see him giving up any time soon.

  7. #7
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    All I said was "Mitochondria DNA puts humans at about 600,000 years old." that was just the tip of the ice burg and I did not want to go into when the first homo sapiens appeared because freakily no one agrees and no one knows.

    Melanin levels very from simple mutations that control the efficiency of melanin production. Such mutations are usually single nucleotide variations: This means that such mutations happen easily and often. Others multi-nucleotide mutations have much harsher effects on whole pigment Opterons causing freckling, Red hair and albinos.

  8. #8
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    I'm unfamiliar with anything significant associated with the 600k yr date. Any book on human evolution written in the last 10yrs will outline the 2 theories I discussed. Those are really the only ones out there with any significant backing.

    Out of curiousity, do you equate "humans" with Homo sapiens? I was assuming you did, since the OP asked specifically about the latter.

    At 600k yrs you have Homo Erectus in Asia, Homo Antecedor (sp?) in Europe, and Homo Ergaster in Africa. Antesdor is thought to have eventually evolved into Neanderthals.

    The mtDNA tracing modern humans (H. sapiens) generally comes in around 150k yrs. I've seen dates as far back as 200k, but nothing more than that. The famouse Klases River mouth fossils are thought to be oldest true Homo sapiens found, and they come in at about 120k years old.

    Check out Tattersall book, Extinct Humans. It's very good.

  9. #9
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    Of course melanin is only one aspect of what people call "race", there are a number of others as well. Skeletons are different and general races are easily identified with just a few bones. Nice explination on skin color, but what about the rest of the variation we see? Why are there differences in hair, for example?s this just an evolutionary accident (unlike skin color)?


    If it is so easy to get differences in physical features, why not some differences in mental abilities as well? Should we not accept the differences we keep seeing on IQ tests between races and regions?

  10. #10
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    The Oriental people don't just have different skin color, they also have different eyes, less facial hair, and shorter heights(on average.) How is that explained? How can natural selection select for shorter heights just from the environment, unless those things come with some other benefit, like higher IQ.

    The Vitamin D argument sounds fairly plausible, although I'm still a little skeptical that it could account for all the skin differences. North Americans have almost the same sunlight as Europeans, yet they are very different.

    Also, why did these different homo species die out right after after they evolved into a different branch? Seems strange to me that the only homo species is us, and the closest link still alive is the chimpanzee.

  11. #11
    The minority view, called the Multiregional Hypothesis, states that spaiens evolved all over the world at the same time from earlier forms of Homo. That we've basically been one species for the last ~2M yrs. Homo Erectus in Asia, Home Neanderthalenis in Europe, and Homo Ergastor in Africa all were really the same species that interbred and evolved into us. Check out books by Milford Wolpoff on this theory.
    I would strongly disagree here. Has there ever been a case of parallel evolution? If you isolate one group from another, give it a few hundred thousand years and they won't be able to breed anymore, therefore they will be different species. I don't believe that we could have bred with neanderthals or erectii, correct me if I am wrong

    If it is so easy to get differences in physical features, why not some differences in mental abilities as well? Should we not accept the differences we keep seeing on IQ tests between races and regions?
    To briefly get political, I can see what you're getting at. I don't think I need a source to say that white kids score better on IQ tests than black kids. Why is this? Because, not to generalize or anything, but the inner city areas, at least in the US, where blacks go to school, are poor and cannot be compared to the suburban schools (like mine) that recieve huge amounts of funding. They don't recieve the same education, so they don't do as well on tests that are meant to measure that education. That's why we have affirmative action: these kids don't get the chance to get a proper education unless they're a step ahead of the rich white assholes that live everwhere else.

    Jews do well on these because I've heard that it's in our culture to learn and to be educated. I'm not a practicing jew so I couldn't really tell you any more than that.

    But, anyway, in the US, blacks have always been under the other races, because of slavery, because of prejudice. Stop the prejudice, put them on an equal footing, and I have no doubt that the scores will improve and be the same as us white folk

    Yo soy un Homo habilis....

  12. #12
    Also, why did these different homo species die out right after after they evolved into a different branch? Seems strange to me that the only homo species is us, and the closest link still alive is the chimpanzee.
    Come on man, we killed them and ate them! Society was only a few thousand years old, whaddya expect?

  13. #13
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    Hair: Just a mutation, odd colors like blonde and the extremely receive red may have been look at as attractive; but hair color change is normally just a neutral mutation.

    Eye: Just like hair although brown irises filters out more background-light from reaching the retina then blue irises do. Red irises are the worst.

    Height: Control by the amount of food available both genetically and environmentally.

    Nose size: Desert people that have to breathe in a lot of sand tend to have bigger noses. The theory is that the bigger nose filters out more sand.

    Other differences: I donít think I have seen any studies on things like why Asian have those eyes and so forth.

    IQ: Intelligence varies greatly through people of the same race. Even if say Indians (from India) have a tendency to be math geniuses this trend does not represent the whole population. The mental capabilities of a person can not be determined by there race but by individual testing. So there are infect black men that are smarter then most white men. Indians that are bad at math and engineering, Asians that donít know martial arts, Jews that are not evil, ect ect. To see what Iím getting at should I go measure the IQ of a bunch of red necks, take the result and proclaim all whites idiot bigots?

  14. #14
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    IQ was just an example (one that fires up emotion). IQ looks for a general ability (called the g-factor), that makes one intellegent compared to others. But subtest look at specific things- spacial abilities, various verbal abilities, ect. Is it hard to see that these could differ by race based on natural selection leading to at least some of the differences we see, even if they are trivial?

  15. #15
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    Originally posted by WellCookedFetus

    IQ: Intelligence varies greatly through people of the same race. Even if say Indians (from India) have a tendency to be math geniuses this trend does not represent the whole population. The mental capabilities of a person can not be determined by there race but by individual testing. So there are infect black men that are smarter then most white men. Indians that are bad at math and engineering, Asians that donít know martial arts, Jews that are not evil, ect ect. To see what Iím getting at should I go measure the IQ of a bunch of red necks, take the result and proclaim all whites idiot bigots? [/B]
    There are a number of things wrong with this. First, the "red necks" are a cultural group, not a biological one. The only way this can apply is if you deny the concept of race to begin with. Second, tests are individual, but results are not. The standard of measure is in fact the group as a whole. To claim a group cannot be used in looking at IQ would amount to the denial of IQ, because IQ is only valid if you compare scores to the group. Third, we know that education can alter IQ for any race. I do not suggest anyone deny this, only control for it when scores are measured. Statistics seem to support that some races differ in some respects. The sexes differ too, but only on subtests, not overall (any overall differences have been eliminated on purpose).

  16. #16
    I'm just going for a walk... ElectricFetus's Avatar
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    Thatís right! Lest say that the group as a whole of all white people are on average 20% smarter then black people, But if you looked at each person individual you would see that there is a lot of smart blacks and a lot of stupid whites. So should we use raw statistics and say well if they are black lets not give them any respect because they are more likely to be stupid or should we jugde people on a more individual level?

  17. #17
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    Originally posted by WellCookedFetus
    Thatís right! Lest say that the group as a whole of all white people are on average 20% smarter then black people, But if you looked at each person individual you would see that there is a lot of smart blacks and a lot of stupid whites. So should we use raw statistics and say well if they are black lets not give them any respect because they are more likely to be stupid or should we jugde people on a more individual level?
    This is moral reasoning, and as such, you are absolutely right. People should only be judged as individuals and accepted and tolerated for who they are...not what they look like or what culture they grew up in.

    However, this is a thread about the science of race, not the moral ideas we should take. Differences cannot be ignored in science, else we are doing a great injustice. There may be a number of important results of knowing differences among groups of people. One fine day, a long time ago, the government decided to contribute all kinds of money to the research of flies. People thought they were insane for giving so much away to fly research. Now that we have finnished the human genome, we know we got our moneys worth. You never know where knowledge can take you. Ignorance on moral grounds is ignorance I cannot accept.

  18. #18
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    Pollux:

    "I would strongly disagree here. Has there ever been a case of parallel evolution? If you isolate one group from another, give it a few hundred thousand years and they won't be able to breed anymore, therefore they will be different species. I don't believe that we could have bred with neanderthals or erectii, correct me if I am wrong"

    Not what I meant to say with regards to the Multiregional Hypothesis. The different groups are NOT seperate species, but one large breeding population. Genes were traded back and forth so that the whole population evolved in concert. Additionally, the Multiregional guys claim that the see indications of modern racial varitions even back as far as 500k yrs. This, by the way, is VERY controversial.

    Perrsonally, I stand with the Out of Africa folks and not the Multiregionals.

    As for H. sapiens breeding with Neanderthals or Erectus, the jury is still out. The little evidence there is indicates there was no interbreeding, but the sample size is very small. Most anthropolgist are comfortable putting Neanderthals in a seperate species and saying there was little or no interbreeding w/ sapiens.

    I don't have data to back this up, but I'd be surprised if sapiens and Neanderthals could not interbreed. Maybe the didn't very often for cultural reasons, but it just doesn't seem that the species were seperated long enough (est at ~600k yrs) to disallow hybridation. Just my opinion, though.

  19. #19
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    Iím not say not to study the difference between races Iím say that whatever the results they won't matter because it is the individual that we have to focus on in the end. With modern bio-informatics we will be able to analyze the genome of a individual and tell him/her exact chances for a disease instead of giving them a very rough guess based on there race.

  20. #20
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    Fetus:

    Good point. Hopefully the more we learn about genetics, the more we'll realize that the differences within a group are larger than the differences between groups.

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