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Thread: Human Brain May Still Be Evolving

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    Post Human Brain May Still Be Evolving

    Originally posted on Dodona by Melnorme:

    http://www.nytimes.com/2005/09/08/sc...;amp;hp=&ex=11 26238400&adxnnl=0&partner=homepage&adxnn lx=1126212523-Sy51vhmKhac0/YQeUBpASA&pagewanted=all

    Researchers Say Human Brain Is Still Evolving

    By NICHOLAS WADE
    Published: September 8, 2005

    Two genes involved in determining the size of the human brain have undergone substantial evolution in the last 60,000 years, researchers say, suggesting that the brain is still undergoing rapid evolution.

    The discovery adds further weight to the view that human evolution is still a work in progress, since previous instances of recent genetic change have come to light in genes that defend against disease and confer the ability to digest milk in adulthood.

    The new finding, reported by Bruce T. Lahn of the University of Chicago and colleagues in the journal Science, could raise controversy because of the genes' role in determining brain size. New versions of the genes, or alleles, as geneticists call them, appear to have spread because they enhanced the brain's function in some way, the report suggests, and they are more common in some populations than others.

    But several experts strongly criticized this aspect of the finding, saying it was far from clear that the new alleles conferred any cognitive advantage or had spread for that reason. Many genes have more than one role in the body, and the new alleles could have been favored for some other reason, these experts said, such as if they increased resistance to disease.

    Even if the new alleles should be shown to improve brain function, that would not necessarily mean that the populations where they are common have any brain-related advantage over those where they are rare. Different populations often take advantage of different alleles, which occur at random, to respond to the same evolutionary pressure , as has happened in the emergence of genetic defenses against malaria, which are somewhat different in Mediterranean and African populations. If the same is true of brain evolution, each population might have a different set of alleles for enhancing function, many of which remain to be discovered.

    The Chicago researchers began their study with two genes, known as microcephalin and ASPM, that came to light because they are disabled in a disease called microcephaly. People with the condition are born with a brain that is much smaller than usual, often with a substantial shrinkage of the cerebral cortex that seems a throwback to when the human brain was a fraction of present size.

    Last year Dr. Lahn, one of a select group of researchers supported by the Howard Hughes Medical Institute, showed that a group of 20 brain-associated genes, including microcephalin and ASPM, had evolved faster in the great ape lineage than in mice and rats. He concluded that these genes may have played important roles in the evolution of the human brain.

    As part of this study, he noticed that microcephalin and ASPM had an unusual pattern of alleles. With each gene, one allele was much more common than all the others. He and his colleagues have now studied the worldwide distribution of the alleles by decoding the DNA of the two genes in many different populations.

    They report that with microcephalin, a new allele arose about 37,000 years ago, although it could have appeared as early as 60,000 or as late as 14,000 years ago. Some 70 percent or more of people in most European and East Asian populations carry this allele of the gene, as do 100 percent of those in three South American Indian populations, but the allele is much rarer in most sub-Saharan Africans.

    With the other gene, ASPM, a new allele emerged some time between 14,100 and 500 years ago, the researchers favoring a mid-way date of 5,800 years. The allele has attained a frequency of about 50 percent in populations of the Middle East and Europe, is less common in East Asia, and found at low frequency in some sub-Saharan Africa peoples.

    The Chicago team suggests that the new microcephalin allele may have arisen in Eurasia or as the first modern humans emigrated from Africa some 50,000 years ago. They note that the ASPM allele emerged at about the same time as the spread of agriculture in the Middle East 10,000 years ago and the emergence of the civilizations of the Middle East some 5,000 years ago, but say any connection is not yet clear.

    Dr. Lahn said there may be a dozen or so genes that affect the size of the brain, each making a small difference yet one that can be acted on by natural selection. "It's likely that different populations would have a different make-up of these genes, so it may all come out in the wash," he said. In other words, East Asians and Africans probably have other brain enhancing alleles, not yet discovered, that have spread to high frequency in their populations.

    He said he expected more such allele differences between populations would come to light, as have differences in patterns of genetic disease. "I do think this kind of study is a harbinger for what might become a rather controversial issue in human population research," he said. But his data and other such findings "do not necessarily lead to prejudice for or against any particular population."

    A greater degree of concern was expressed by Francis Collins, director of the National Human Genome Research Institute. He said that even if the alleles were indeed under selection, it was still far from clear why they had risen to high frequency, and that "one should resist strongly the conclusion that it has to do with brain size, because the selection could be operating on any other not-yet-defined feature." He added that he was "worried about the way in which these papers will be interpreted."

    Dr. Sarah Tishkoff, a geneticist at the University of Maryland and a coauthor of both studies, said the statistical signature of selection on the two genes was "one of the strongest that I've seen." But she said, like Dr. Collins, that "we don't know what these alleles are doing" and that specific tests were required to show they in fact influenced brain development or were selected for that reason.

    Dr. Lahn acknowledges this point, writing in his article that "it remains formally possible that an unrecognized function of microcephalin outside of the brain is actually the substrate of selection."

    Another geneticist, David Goldstein of Duke University, said the new results were interesting but that "it is a real stretch to argue for example that microcephalin is under selection and that that selection must be related to brain size or cognitive function."

    The gene could have risen to prominence through a random process known as genetic drift, Dr. Goldstein said.

    Richard Klein, an archaeologist, who has proposed that modern human behavior first appeared in Africa because of some genetic change that promoted innovativeness, said the time of emergence of the microcephalin allele "sounds like it could support my idea."

    But if the allele really did support enhanced cognitive function, "it's hard to understand why it didn't get fixed at 100 percent nearly everywhere," he said. Dr. Klein suggested that perhaps the allele had spread for a different reason, that as people colonizing East Asia and Europe pushed northward they had to adapt to much colder climates.

    Commenting on these critics' suggestions that the alleles could have spread for some reason other than their effects on the brain, Dr. Lahn said he thought such objections were in part scientifically based and in part due to reluctance to acknowledge that selection could occur in a trait as controversial as brain function.

    The microcephalin and ASPM genes are known to be involved in determining brain size and so far have no other known function, he said. They are known to have been under selective pressure during primate evolution as brain size increased, and the chances seem "pretty good" that the new alleles are a continuation of that process, Dr. Lahn said.

    Dr. Lahn said he had tested the possibility that the alleles had spread through drift, as suggested by Dr. Goldstein, and found it was very unlikely.
    Its probably a first step to prove in the genes what many scientists and my person said, that progressive Eurasians (Europids and Mongolids) have undergone a strong selection, evolved on in the classical Homo direction - evolution of the brain and behaviour, especially during the LGM, whereas those living in areas comparable to the original Homo environment in Africa had a much slower development, partly, especially in isolated populations like in Australia almost none.
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    Post Re: Researchers Say Human Brain Is Still Evolving

    Which factors do you think have made Eurasians more intellectually advanced?

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    Quote Originally Posted by www.ctv.ca
    That the genetic changes have anything to do with brain size or intelligence "is totally unproven and potentially dangerous ..."
    Yes it is - for the scientist and his career.

    Quote Originally Posted by www.ctv.ca
    Lahn's testing did find geographic differences in populations harboring the gene variants today. They were less common in sub-Saharan African populations, for example.
    Oh, that's surprising. : :negro000:

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    "May still be evolving"... Man's arrogance never ceases to amaze me. What would make anyone think this is the pinnacle of human development? Certainly, the way things are going it probably will be as we will destroy ourselves, but this sort of thinking disgusts me just as much as religious babble concerning Man being some god's greatest (and final) creation.

    Evolution wont stop just because we're smart enough to know it exists. What we would eventually evolve into I dont know, but by following the development in the past some guidelines would be; larger (or more complex) brain, thinner skeletal structure etc.

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    Post Re: Researchers Say Human Brain Is Still Evolving

    Quote Originally Posted by Northern_Paladin
    Which factors do you think have made Eurasians more intellectually advanced?
    The harsh and instable climate, the need for planning especially through the winter. Its well known that in general, both for Europids and progressive Mongolids of the Northern regions life was different, they had to plan, they lived in bigger groups, hunted in complex organised units, had an improved social system, different kind of sexual selection because both the male and the female had to rely much more on each other and a male could take every female, but he thought twice whether it was worth the investment, because it could be his only chance, again different from certain tropical regions.

    Furthermore the Mongolids themselves had the advantage of producing a skin type which was versatile, if you compare the variation of Europid skin in the same climatic regions with that of Mongolids, you will be impressed by the more stable Mongolid condition. I dont want to explain the whole Mongolid skin structure now, but I can just say it seems to be, like the other features, an adaptation to the UV-rich open regions of the Cold and brought up a type which could survive both in rather UV-poor and rich areas easier without extreme variation (like Europids).

    Other features of the Mongolid type are the social adaptation, lower level of individual aggression and less extreme masculine tendencies. (Negrids are in fact the opposite). They are a very frugal, partly simple type which can stand suffering better, especially in social unity if its about the typical Mongolid variant. Of course culture evolved in the same direction because of the same reasons and needs.
    I think the basic tendencies came up during the LGM in which the former bigger groups melted down in the worst time to small groups which had to fully cooperate, stand suffering and acting planned to survive and reproduce again. After this type evolved, and because parts of East Asia were still quite primitive, this specialised groups almost explode and pushed others away, next wave followed and pushed the last, which ...
    Like the big ancient migration of the Germanic people, one pushed the other, just with the difference that this people had a bigger impact genetically, because the density was low in the LGM. After that they had already the North of Asia and Northern China, but still not the whole region. That came with rice expansion, the Neolithic spread of this type...and this time the same thing happened as before, just with much more people and with other cultural features.
    We can differ two types of basic Mongolids, the Arctic (Tungid and related) and the Sinid (and related) with the later having an influence of the South from early on, but during the selection period the primitive features were mostly bred away and finally produced an even more progressive type.

    Aesthetic selection is not inevitably correlated with psychological improvements, especially not with intelligence, but more with hormonal status and personality.
    The intelligence selection was independently stronger in the temperate and cold climate and bigger social units (in the tropics were even at the time of H-G the groups smaller) for which less aggressive intragroup behaviour but the ability to use disciplined aggression in the intergroup selection was crucial.

    So, there could be primitive looking groups on this planet which are more intelligent, but as things are, that is not the case because the evolution which lead to new physical adaption away from the tropical types was crucial for the higher intelligence and social more adapted behaviour too.

    Furthermore a good physical shape and condition, both efficiency and attractiveness are important features on their own. You say that are only attractive features, but thats not true, they go deeper and are on-line with the past evolvement of humanity. I made other threads and posts about that topic, especially about skull hole (foramen magnum) position-orthognathy-spine evolution...
    Furthermore you can have mixed status, f.e. certain progressive features combined with primitive (most obvious full lips with prognathy).

    The correlation between general attractiveness and average higher intelligence is proven and whats proven too is that chances are higher that partner selection leads to the combination of attractiveness and intelligence.

    F.e. under extreme selection in a new environment, what kind of women will the more intelligent and stronger male take? The ugly, primitive and less healthy looking? Especially if he must do more for her, because in the tropics the women can go on and work for their own nutrition and probably the children too, the male must not be always there or successful. Especially during the last LGM the males had oftentimes the full responsibility to care for the women and children nutrition - they must be successful and intelligent hunters and attack others for, or defend their own winter ressources.
    Under the tropical conditions males didnt selected so much and females neither, they both looked just to reproduce and that the body is strong and healthy, the character of the person, the sympathy in the face was probably less important because investment and risk was lower too.
    A male during the LGM might have been investing all he had of energy in just 4 children of one or two women, if they were treacherous or unhealthy, had no good genes themselves his life was lost. Especially if he went on his long hunting work he had to rely on the ability and fidelity of the woman.
    Most small tropical hunters went with their women or didnt used such a great radius as the Northern H-G groups with their bigger social systems in which single male aggression without discipline couldnt be tolerated.
    To think ahead, especially if its about planning a family and surviving the winter was crucial.
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    eugenics

    the idyllic life-style
    on the exposed continental shelf
    during the last ice-age,

    posed few challenges
    to the inhabitants
    and, consequently,
    few adaptations took place.

    contrastingly, the inhabitants
    of the interior
    of the eur-asian continent
    were harshly challenged
    by the environment
    and some evolved
    into the most advanced human form.

    certainly, nordic man
    (before christianisation and urbanisation)
    was the most genetically gifted
    and had the maximal expression of genetic material
    yet seen in humans.

    where else is to be seen
    such a grand combination
    brains and brawn?

    erlingr's insistence on
    nordic man/nordic culture/nordic land
    is purposeful.


    if it is lacking,
    man will continue to evolve
    in to what ever varietal niches
    are available.

    self-conscious man should direct his life
    and, at a minimum, that of his descendents.

    challenge your self:

    "let me strive every moment of my life
    to make my self better and better,
    to the best of my ability".
    Quote Originally Posted by perkele14
    Otherwise it is all pointless mental masturbation.

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    Post Re: Researchers Say Human Brain Is Still Evolving

    As for the 2nd variant I think its definitely correlated with Neolithisation and there Indoeuropeanisation too. Many people argued in the past that no new mutations of significance came up in the last 10.000 years, whats absolute nonsense and many people recognised this. Evolution doesnt stop, both to higher and lower forms (degeneration) it can go on and the post-Neolithic lifestyle made up totally new selective regimes with a positive peak in the late Neolithics and Bronze Age.
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    Post Re: Researchers Say Human Brain Is Still Evolving

    Dienekes added some more information and theories on his own in his blog:
    http://dienekes.blogspot.com/2005/09...-on-brain.html
    Its interesting to see how low the percentages in Subsaharan Africans (Negrids, Bambutids, Khoisanids) is. Some Pygmies, which are my prime example for a group which was pushed away poor regions, had to reduced their type in this negative environment and further infantilised AND show very primitive-plesiomorphic traits have frequencies of ASPM haplogroup D of 0 percent.
    The only surprise: If the results are representative, Melanesids, mainly the Neomelanesid Papuans have quite high percentages of both allels.
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