isa
Craftsperson
Posts: 15
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Post by isa on Jan 5, 2013 15:11:06 GMT -5
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Post by zarahan on Jan 8, 2013 14:31:54 GMT -5
Excellent work. I found the following blurb interesting.. natural selection may at times be only of minor importance. Something to keep in mind when we hear assorted "biodiversity" types claim that this is "selected for" and that is "selected for". Really? -------------------------------------------- "It may appear counterintuitive, but a large part, if not the majority, of genetic change in human populations is not thought to be due to natural selection but rather due to the play of chance (genetic drift; Harris and Meyer, 2006; Li et al., 2008; see Table 2 for a glossary of terms frequently used in population genetics). Many opportunities for chance can occur in the transmission of alleles from parents to offspring, and evidently did occur as part of the demographic process of dispersal out of Africa. Thus, finding differences in the frequency of alleles at a particular locus between populations is not an evidence of natural selection per se. The default position is that of neutral theory, whereby chance events account for most patterns of genetic diversity (Harris and Meyer, 2006). Of course, deleterious mutations will be selected against (purifying selection) and beneficial mutations may increase in frequency to fixation, but overall these events will contribute little to explaining the presence of most polymorphisms." --J. Rees and R. harding 2011. Understanding the Evolution of Human Pigmentation: Recent Contributions from Population Genetics. Journal of Investigative Dermatology. 358 The same limitation is noted by Dr. A. Oubre in debunking race based science - quote: "How do we know for certain whether a trait evolved through natural selection or instead, through a neutral evolutionary mechanism of genetic drift? This question (as well as any answers we may offer) is fundamental to understanding the adaptive significance, if any, of population-based (or race-based) differences in functional traits.
Many experts maintain that although natural selection plays a critical role in the evolutionary origin of many traits, it is not the driving force behind all biological phenomena. In fact, according to some evolutionary biologists who conduct empirical field research, genetic drift is typically assumed by default to account for most traits. Proving that natural selection is involved in the origin of a particular trait is a complicated process. Given the complexity of natural selection, it is not surprising that biologists cannot ascertain if there are long term differences in traits that have evolved through natural selection versus those that emerged through neutral selection. 3
There are other enigmas that must be sorted out as well if we are to identify the features that distinguish natural selection from neutral selection. For instance, genetic drift tends to be more influential in small populations while natural selection is more powerful in large populations. The microevolution of human races that occurred over the past 15,000 to 30,000 years affected smaller human populations. At the same time, however, natural selection had a momentous impact on the evolution of certain anatomical and physiological traits in larger geographical populations. Both genetic drift and selection could have operated in tandem to initiate the emergence of different traits in the same populations, or in clusters of geographical populations.
Positive natural selection increases fitness, which is measured in terms of survival and reproduction. However, natural selection may act on different levels of biological organization, even simultaneously at times. Classic bioevolutionary studies emphasize the influence of natural selection on individual organisms, populations, and even species. Yet, selection can also act at the level of the genome, chromosomes, and genes (DNA sequences). "The Adaptionist Yardstick: Rethinking the Social Implications of Sarich’s and Miele’s Fast-Track Micro-Evolution A REVIEW BY ALONDRA OUBRÉ, Ph.d. Medical Anthropologist
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Post by forwardever on Oct 6, 2013 0:21:58 GMT -5
What are the implications of this and other recent/current research in explaining the variations in skin color in northeast Africa. I am especially interested in the region of modern day Ethiopia. I've read that Black Africans migrated out of Africa into Asia and that those events preceded the appearance of lighter skin colors. here's a reference on Wiki: "Human genetic variation, Race and genetics, and Human genetic clustering Genetic studies have discovered a number of genes that affect human skin colour across different populations. These studies suggest a 3-way model for the evolution of human skin colour, with dark skin evolving in early hominids in sub-Saharan Africa and light skin evolving separately in Europe and East Asia after modern humans had expanded out of Africa.[8][9][10][11][12][13] Dark skin[edit] All modern humans share a common ancestor who lived around 200,000 years ago in sub-Saharan Africa.[14] Comparisons between known skin pigmentation genes in chimpanzees and modern Africans show that dark skin evolved along with the loss of body hair about 1.2 million years ago and is the ancestral state of all humans.[15] Investigations into dark skinned populations in South Asia and Melanesia indicate that skin pigmentation in these populations is due to the preservation of this ancestral state and not due to new variations on a previously lightened population.[5][16] " en.wikipedia.org/wiki/Human_skin_colorIs this information essentially correct and is the back migration to Africa by lighter skinned people the PRIMARY reason for lighter skin colors in some parts of Ethiopia and in other places like Eritrea? Thanks in advance!
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Post by anansi on Oct 6, 2013 5:43:39 GMT -5
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Post by truthteacher2007 on Oct 6, 2013 19:51:39 GMT -5
I think te difference in the two groups can be explained by environment. If the San were the first in that area, then it stands to reason that they were there long enough to adapt to the environment, where as their neighbors are more recent arrivals. How else can we explain that Native Americans in the same tropical latitudes do not have as dark a pigmentation as other populations who do?
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Post by djoser-xyyman on Oct 6, 2013 20:37:56 GMT -5
Answer is here. See the White West African thread(2013) x xx The illustration tells a story. As the author states African left the continent with light skin!!!! No admixture needed. I am of the firm belief as such. I said light...not white Heather Norton (of Kittles fame) is of the same oppinion. Any more questions..post.
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Post by djoser-xyyman on Oct 6, 2013 20:41:10 GMT -5
I also came across another recent study supporting the same hypothesis. Will post on it when I have time. Africans CARRY the genes for light skin. Remove the constraint...and boooooom!!!Norton, Shriver, Rees..three of the leading experts on skin pigmentation came to that conclusion.
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Post by azrur on Oct 7, 2013 20:27:16 GMT -5
can someone just say the tldr version which will obviously be all non blacks are albinos negroid master race? i dont care for genetics because it is fake and disproved by the bible
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Post by djoser-xyyman on Oct 8, 2013 5:05:36 GMT -5
??
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Post by azrur on Oct 8, 2013 8:06:17 GMT -5
the research is basically saying all non blacks are genetic inferior albinos? that was what it was on the last egyptsearch why not on here?
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Post by anansi on Oct 8, 2013 10:42:49 GMT -5
the research is basically saying all non blacks are genetic inferior albinos? that was what it was on the last egyptsearch why not on here? Because here is NOT Egyptsearch!! we do not believe in genetically inferior human beings and the genetic stuff will go over your head because you reject genetic studies and relie on the Bible on principle, but most whites as far as I know are not Albinos as that condition came from a different trigger.
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Post by djoser-xyyman on Oct 9, 2013 19:45:01 GMT -5
He is here to push your buttons..He hasn't made a credible argument as yet..ignore him for now...until he starts to be disruptive.
I am open to any intelligent argument....
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Post by azrur on Oct 9, 2013 19:50:24 GMT -5
He is here to push your buttons..He hasn't made a credible argument as yet..ignore him for now...until he starts to be disruptive. I am open to any intelligent argument.... credible argument against what?
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Post by forwardever on Oct 9, 2013 22:39:51 GMT -5
Thanks to everyone who has responded to my question.
I note that the interesting maps showing ancestral and "derived" skin color show NO results in the northeast part of Africa.
Would someone define "derived" for a layman? Is "derived" essentially equivalent to results from "admixture."
I am most especially interested in that area of The Continent - the region around modern Ethiopia.
Let me be more precise with my question. While the African has the capacity to create lighter skin color...
Is the PRIMARY reason for significantly lighter skin color in that area of the Continent due to "internal" genetic capability? OR Is the PRIMARY reason the admixture with those who migrated to or invaded that area?
Thanks in advance!
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Post by truthteacher2007 on Oct 9, 2013 23:08:40 GMT -5
Thanks to everyone who has responded to my question. I note that the interesting maps showing ancestral and "derived" skin color show NO results in the northeast part of Africa. Would someone define "derived" for a layman? Is "derived" essentially equivalent to results from "admixture." I am most especially interested in that area of The Continent - the region around modern Ethiopia. Let me be more precise with my question. While the African has the capacity to create lighter skin color... Is the PRIMARY reason for significantly lighter skin color in that area of the Continent due to "internal" genetic capability? OR Is the PRIMARY reason the admixture with those who migrated to or invaded that area? Thanks in advance! I don't know what the term, "derived" means, but here are my 2 cents on the question. I believe that the lighter skin tones found in north Africa are due to two factors. Firstly, North Africa is not a tropical, but a sub tropical region. Therefore, it is not out of the question that long term residents in the region developed lighter skin tones as an adaptation. This is not unique to Northern Africa alone. The San of the Kalahari in Southern Africa also live in a sub tropical zone. They are known to exhibit a high percentage of individuals with light brown or yellowish skin tones. In fact, this is quite common. The second factor contributing to light skin tones is admixture with lighter skinned populations who migrated into the region. This has certainly been a contributing factor in historical times. So while admixture is a contributing factor, it is not the only factor, nor is it always the case in every situation. Also keep in mind that like the south, the nort has never been isolated from tropically adapted peoples migrating in from the south. To this day one can still find significant numbers of people in every country and region of North Africa with tropically adapted skin tones. You would be surprised to see that even in a city like Alexandria or Ismaliya in Egypt a significant percentage of the population is just as dark as people as far soth as Aswan. The region has always been deverse and is likely to always remain so.
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