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Author | Topic: Multi-regionalism and Probability | |||||||||||||||||||||||
sfs Member (Idle past 2564 days) Posts: 464 From: Cambridge, MA USA Joined: |
quote:An Out of Africa model is supported not just by mtDNA, but by X, Y and autosomal data. As far as genetics is concerned (and genetics is very powerful here), full multiregional models are dead. The choice at this point is between complete genetic replacement by African migrants and merely large-scale replacement. The bulk of loci point to an African origin. A few loci look like they may represent introgression from archaic Homo outside the African line, although none are considered conclusive. (One of the most suggestive, if I remember correctly, is the chromosome 17 inversion found by deCODE Genetics.) I have never seen a strong case made that MC1R (the "ginger gene" you referenced) is in this category. The link you posted is hard to do anything with, since it's just a news report, with no attached paper. The scientist quoted, Rosalind Harding, doesn't seem to have published anything supporting this claim. The paper she (and others) did publish on MC1R (Am. J. Hum. Genet. 66:1351-1361, 2000 -- a fine paper) doesn't reach any such conclusion; it finds the European variants in the gene to have an age consistent with other loci examined. Estimates of total genetic diversity lead to the same conclusion. The effective population size of humans 100 - 200 thousand years ago was 10-15,000. It is very hard to see how a population that small could have been spread out across Africa, Europe and Asia while still maintaining the high levels of gene flow needed to keep regional differentiation in check.
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1.61803 Member (Idle past 1535 days) Posts: 2928 From: Lone Star State USA Joined: |
Hello..
quote:Agreed..but I can assure it does not stop theorist from generating some doozys...to include String theory and it's spin offs or the mating habits and rituals of extinct taxa. It sucks when the facts get in the way of a good hypothesis. Edited by 1.61803, : typos "One is punished most for ones virtues" Fredrick Neitzche
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Jon Inactive Member |
An Out of Africa model is supported not just by mtDNA, but by X, Y and autosomal data. As far as genetics is concerned (and genetics is very powerful here), full multiregional models are dead. Are they, really?
quote: In whatever way these "scientists" are reading the DNA evidence, they are making a mistake. The genetics should show a rather agreeable date, but it shows really old mtDNA populations, and relatively younger Y-chromosome DNA populations; this is only explainable if we realize that current methods for genetic reading are semi-(if not entirely)-flawed. I believe that the genes that define our sapiens variation may, indeed, have arisen mostly in African populations, but that these genes (not the individual creatures themselves) spread through interbreeding, slowly becoming incorporated into already existing populations of what we would call H. erectus, and slowly altering what is really the erectus variety of Humans to become the modern variety. Other "human" traits could also have arisen in other population outside of Africa, and spread to the rest of the erectus world. And then:
quote: Genetic studdies seem glitchy at best for OOA, and at the far end, seem to support MH moreso. Now, I should really be puting this in my report . Laters. Max ________________Chris Stringer and Peter Andrews. The Complete World of Human Evolution (New York: Thames & Hudson Inc., 2005), 177. Ibid., 177.
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jar Member (Idle past 425 days) Posts: 34026 From: Texas!! Joined: |
In whatever way these "scientists" are reading the DNA evidence, they are making a mistake. And you base that revelation on??????????
The genetics should show a rather agreeable date, ... Why?
... but it shows really old mtDNA populations, and relatively younger Y-chromosome DNA populations; Correct.
this is only explainable if we realize that current methods for genetic reading are semi-(if not entirely)-flawed. Why? Would it not be possible to have a bottleneck incident where many males came through but few females? After that point in time all the descendants would carry the genes of those few women but also of any of the men. Would it not be possible at some later time to have a bottleneck incident where many women came through but few males. After that point in time all the descendants would carry the genes of those few men but also of any of the women. Aslan is not a Tame Lion
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sfs Member (Idle past 2564 days) Posts: 464 From: Cambridge, MA USA Joined: |
quote:Yes, they're really dead. Pushing up daisies. quote:Sorry, but that's wrong -- there are several reasons for the Y chromosome and mtDNA to have different ages. One is different effective population sizes. It is common for human males to take multiple mates, meaning the number of breeding males is smaller than the number of breeding females; smaller effective population size implies a smaller expected age of the locus. Natural selection may also be quite important on both the Y and mtDNA. Since neither recombines, an advantageous mutation anywhere on either will sweep the entire chromosome to fixation with it, dramatically lowering the diversity and the age estimate. This is why neither the Y nor mtDNA is a good clock for measuring demographic history. Finally, even if no other processes are at work, the random variation in the age for a single locus (and mtDNA and the Y each act as a single locus) is very large. The expected time to the most recent common ancestor for these loci is N/2, where N is the effective population size. The estimated N for humans is in the range of 10 to 15 thousand, giving an expected age of ~100 - 150 thousand years. The standard deviation on the age, however, for different loci is also equal to N/2, so the expectation is for 100,000 +/- 100,000 years. Finding one at 70,000 and one at 180,000 (or whatever particular estimates you like) is not surprising at all.
quote:Even under a purely Out of Africa model (which there's no reason to believe is correct), one would expect to find some loci that look like they root outside Africa (see Takahata, Lee and Satta, "Testing Multiregionality of Modern Human Origins", Mol Biol Evol. 2001 Feb;18(2):172-83.) There are indeed some loci that look like they represent an archaic non-African admixture (although I haven't seen betaglobin proposed that way that I can remember -- what paper does the book cite?), and that may be what they are; a better example might be the X-linked locus discussed in Garrigan D, Mobasher Z, Severson T, Wilder JA, Hammer MF, "Evidence for archaic Asian ancestry on the human X chromosome", Mol Biol Evol. 2005 Feb;22(2):189-92. But the large majority show Africa as the root. So a contribution of 5 or 10 percent of non-African ancestry is quite plausible, but 50% is not.
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Jon Inactive Member |
My report:
Extension was given by instructor for the report, so I removed the link for now It should serve as an effective response to questions about why I do not find mtDNA evidence convincing as absolute proof for OOA. I would like to ask that this report does not recieve the same treatment as my last I posted. Do not attack the style of the report, or how it's written, or the language used, or the conventions, or its straigh-forwardness/lack thereof. Instead, I want to address its content, and how the argument pertains to the subject of this thread. I am not posting this paper as an effort to show off my writing any more than a post on the boards could be seen as such an effort. It is, like any post, meant to convey the information, and it is the information on which I am hoping you will all focus. Why I post this as a paper instead of as a standard post is simply for the fact that I have already written this once, and do not wish to do so twice. Jns Edited by Jns, : halvzees, onzees, twozees! :- Edited by Jns, : Removed link. In considering the Origin of Species, it is quite conceivable that a naturalist... might come to the conclusion that each species had not been independently created, but had descended, like varieties, from other species. - Charles Darwin On the Origin of Species
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Wounded King Member Posts: 4149 From: Cincinnati, Ohio, USA Joined: |
First, mtDNA codes for”or produces”very few things in our body; save for an occasional protein, mtDNA is completely useless3 This is just stupid. Without mtDNA you wouldn't have any functional mitochondria and you wouldn't be alive. You wouldn't just be ill or have a severe developmental defect you would never have got beyond being a one celled zygote. This just seems as if you have no idea what mitochondria are.
Without mixture from the father, the only variations arising in mtDNA are natural mutations resulting from copying mistakes during conception. This isn't right, there is no particular significance to conception. It would be more correct to say mtDNA only accrues mutations arising in the maternal germ line. It might also be a good idea to say why this is and why mtDNA is actually unique, i.e. it is seperate from the nuclear genome and contained in multiple copies in the mitochondria of the cell. It is also thought that there are some rare cases of contribution of paternal mtDNA, which might be at least as big if not a bigger problem for estimates based on an assumption of solely maternal pattern of inheritance than your variations in population density would be.
Because mtDNA doesn't code for many things, these mutations continue to be passed on, i.e., people don't die from the mutations, and so live to pass them on. Again this is wildly wrong. I think what you may need to do is specify that this analysis focuses on a particular stretch of mtDNA called theControl region which doesn't code for any proteins and where mutations are usually considered to be neutral but what is true for the control region is certainly not true for all of the mtDNA. I don't know if this research was based on the control region, but that is the only way I can see any of your statements actually being anything other than plain wrong. Just a few preliminary thoughts. TTFN, WK Edited by Wounded King, : No reason given.
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fallacycop Member (Idle past 5551 days) Posts: 692 From: Fortaleza-CE Brazil Joined: |
There is no need for any bottlenecks at all to explain the evidence.
Picture a culture where mem regularly kill all the men from neighbough tribes, but leave the womem alive (and pregnant). Not to hard to imagined, is it? That would lead naturally to a population for which the genetic analysis of the Y-chromossome's DNA would seem to tell us a different story then the genetic anaysis of the mitochondrial DNA. In fact, it would most probabily give us a more recent "ADAM" and a more ancient EVE.
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jar Member (Idle past 425 days) Posts: 34026 From: Texas!! Joined: |
Isn't that still a bottleneck?
Whether the cause of the disproportionate presence is due to intentional actions or some naturally occurring event, isn't the end result the same. Edited by jar, : No reason given. Aslan is not a Tame Lion
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fallacycop Member (Idle past 5551 days) Posts: 692 From: Fortaleza-CE Brazil Joined: |
Isn't that still a bottleneck? I wouldn't call it a bottleneck because in the scenario I described there isn't necessarily a sharp decrease in the human population. Just a series of sporadic genocydes (like Ruanda or Sudan in modern days). If you add to it the fact that most genocydes were directed towards men, but left many womem alive, you get the result of selectively reducing the Y-chromossome's variability Edited by fallacycop, : typo
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Jon Inactive Member |
My apologies for the incorrect information. That information was taken primarily from the source cited in footnote one of page 2.
Their information on mtDNA is that it is, indeed, rather pointless. I will definately take what you said into my mind, but as for the paper it should not be too big a concern, as the primary points still apply, only they apply in regards to the "control region," instead of to all of the mtDNA strand--I would assume that it is this region that is used in mtDNA analysis of population history. Jon
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fallacycop Member (Idle past 5551 days) Posts: 692 From: Fortaleza-CE Brazil Joined: |
Jns, there is an important aspect to this mitochondrial study that you have not addressed at all.
The study doesn't simply count the number of mitochondrial variants.It also measures the genetic distance between them (this can be taken as a proxy for how long ago the two lineages diverged (whithin statistical fluctuations of course)). And it turns out that all the lineages outside of Africa are more closely related to each other when compared with the lager variety found in Africa. How do you explain that with your model?
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Jon Inactive Member |
quote: In my report, I do not argue in favour of any particular model; instead, I argue against the OOA interpretation of mtDNA data. According to mtDNA, either population fluctuations could explain it or OOA. And so, I argue that neither should be assumed correct. Because the OOA seems to be the currently accepted theory, I decided to focus on it could being wrong slightly more than on why population fluctuations can be equally as wrong. Jon
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fallacycop Member (Idle past 5551 days) Posts: 692 From: Fortaleza-CE Brazil Joined: |
You didn't address the point I made in my previous post, about the lager genetic variability observed among african populations.
I'll give you another one to think about: The MtDNA variation observed in Populations around the world allows us (By us I mean the scientists that did the work) to reconstruct a tree of relationships among those populations. It turns out that all the populations outside of Africa end up allocated in one Branch, while the African populations end up in many branches (That's to be expected by the OOA theory, but is hard to understand from the oposing point of view)
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DBlevins Member (Idle past 3806 days) Posts: 652 From: Puyallup, WA. Joined: |
I want to see the proof that H. sapiens could in fact interbreed with erectus, neandertalensis, and heidelburgensis. Or for that matter, that erectus and neandertalensis could inertreed, or that erectus and heidelgurgensis could interbreed, or any other combination (seeing as how the MRH requires them all being able to interbreed, from what I understand). While so far the evidence for hybridization is weak and mtDNA evidence seems to suggest that there was no gene flow between H. neanderthalensis and H. sapiens, it doesn't rule it out entirely. A study done by Clifford Jolly on the Papionina subtribe of monkeys suggests that hybridization can occur between hominine genera that have diverged as long as 4 mya. It is possible that advantageous genes survived as the hybrid zone shifted. (Jolly, CJ. 2001. A Proper Study for Mankind: Analogies from the Papionin Monkeys and Their Implications for Human Evolution. Yearbook of Physical Anthropology. 44: 177-204). Here is a paper that suggests that there was some hybridization between the populations: Hardy, J. et al. 2005. Evidence suggesting that Homo neanderthalensis contributed the H2 MAPT haplotype to Homo sapiens. Biochemical Society Transactions. 33: 582-585
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