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MITOCHONDRIAL DNA AND PHYLOGENETIC ANALYSIS OF PREHISTORIC NORTH AFRICAN POPULATIONS
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[QUOTE]Originally posted by Amun-Ra The Ultimate: [QB] [QUOTE]Originally posted by xyyman: 3. In other words. These Sudanese Sahara region Great Lakes people seems to be the source of ALL the world's population. ALL REGIONAL SPECIFIC SNPs are found there!!!!! This is s strong indication of the source. Ie ORIGIN. [IMG]http://i41.tinypic.com/24m6af4.jpg[/IMG] [/QUOTE]For one, it's true that all humans come from Africa. But obviously when we study population structure like with haplogroups analysis we study the situation where human started to diversity from one another due to various migrations. We study the differences between humans. We're all humans....with diversified: geographic location, shared history, ethnic groups, cultures, languages, etc. So when we study those population structure, we study those differences between humans, even if the proportion of polymorphic genes between humans is very small. I don't remember the exact number (someone can help). I think the number of SNP in humans is about 0.1%. Each human is born with about 60 to 100 SNP/mutations. That is each human is born with about 100 nucleotides which are different from both our parents (and any grandparents of course). Humans have, 6 billions nucleotide pairs in total in their whole genome. With time, if you have a lot of descendants and those descendants have a lot of descendants too. Your mutations could become a new major haplotype in the future. Which we would define as one of those 60-100 mutations. Although it's more difficult nowadays since the populations sizes are very large and your descendant numbers will most probably always be a drop in the ocean in term of proportion of the overall population size. In ancient time, it was different due to the much smaller population size. For example, the first E-P2 carrier, with a SNP mutation we call P2, is father to lets say about 75% of African people. P2, as any mutation, is also known from other mutation sites/defining mutations like DYS391p, L337, L339, L342, L487, L492, L613, P2/PN2, P179, P180, P181 (taken from wiki). We could probably find something between 60 and 100 of those defining mutation for that haplogroup. Any haplogroup could be defined by about 60 and 100 defining mutations (if we studied the whole genome). At the moment, in those genetic study, we just study specific part of the genome. When you say [b]ALL REGIONAL SPECIFIC SNPs are found there[/b]. It's obviously false. For one, I don't know what you call 'all regional specific SNPs', but haplogroups are an example of regional specific SNPs. In fact, that's what haplogroups are almost by definition. That is: SNPs/Mutations which have some form of regional specificity. It's because those SNPs and Mutations are not common to all humans that we can study them as haplogroups. It is because they are not common to all humans that we can determine when a mutation like M89 or P2 first appeared, where did it appeared first and who's carrying that mutation now, etc. There's other regional specific SNPs which are not studied. Sometimes one or many successive SNPs across generations can affect the phenotype like the sickle cell anemia mutation which conferred some protection against malaria beside its drawback in term of life expectancy. Some other SNPs can lead to being born dead, while some others can be neutral. Usually we consider haplogroups to not be under any selective pressure directly (although there's genetic drift, founder effect, admixture, etc). It was a bit long but it's important to understand why you're wrong when you say [b]ALL REGIONAL SPECIFIC SNPs are found there[/b]. This can easily be seen directly here for example: [IMG]http://www.nature.com/ejhg/journal/v13/n7/extref/5201408x1.gif[/IMG] This is from the study called [URL=http://www.nature.com/ejhg/journal/v13/n7/abs/5201408a.html ][i]Contrasting patterns of Y chromosome and mtDNA variation in Africa: evidence for sex-biased demographic processes by Woods(2005)[/i] [/URL] For example, in your image of different clusters at K=4 and K=7, if you look at the Hema population they seem to have all the color at K=7. But if you study the table above (sorry for the image resolution, its horrible) you can see that the Hema population don't have for example the R-M173 mutation. As well as many others from the R, K, J haplogroups family, among other. [b]Clearly, the great lakes regions doesn't have all the regional specific SNPs in the world. The Great Lakes regions doesn't have all the haplogroups in the world, which are regional specific SNPs. [/b] I think this is obvious when you think about it from that angle. Even in your graph at K=7, the Hema population in the sample doesn't seem have the brown color apparently (its hard to see). At bigger K, it won't share all the color for sure (because sub-population clusters will start to appear). I gave you the long explanation because it's important to understand what SNPs, nucleotides, mutations, and haplogroups are. [/QB][/QUOTE]
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