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Author | Topic: New Type of Ancient Human Found—Descendants Live Today? | |||||||||||||||||||||||
Nuggin Member (Idle past 2523 days) Posts: 2965 From: Los Angeles, CA USA Joined: |
Good post. I've been avoiding this thread because it has become too pedantic. When I studied evolution/fossil man for my Ph.D. exams, I was taught the multi-regional hypothesis. This was some xxxxxx [censored] decades ago. Since then the Out of Africa hypothesis has come to dominate. But there are still some bits of the multi-regional hypothesis which seem to be accurate--those are the same ones that led to that hypothesis in the first place. Overall, it was incorrect, but those some bits remain. Ones I remember from grad school are primarily from Asia, and include such traits as shovel-shaped incisors. These traits, called line traits, show continuity from early populations, such as Home erectus, to modern humans. So whatever model you come up with, obviously some form of OoA, you will need to account for the persistence of a few line traits in eastern Asia. Don't seem like much point to trying to make it OoA _or_ MR. Clearly it's both. Looking at just the Neanderthal genes in populations outside of Africa demonstrates that MR and OoA played a role. Call Neanderthals are "human population" as the cladists would, and you've got gene flow coming from a group which clearly evolved in isolation from the OoA group. Unless the entire argument is being rolled back to "did H. Erectus evolve into three + different populations which each interbred and therefore it's all MR". But if we're doing roll backs, why not just roll it back again and say: "All H. Erectus populations arose from a seeder population which originally arose in Africa". So it's back to OoA. Someone has to set a specific point of reference in order for the debate to have any meaning.
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Dr Jack Member Posts: 3514 From: Immigrant in the land of Deutsch Joined: Member Rating: 9.2 |
Don't seem like much point to trying to make it OoA _or_ MR. Clearly it's both. I don't agree that it's clearly both. Even with the new evidence, the MR is still wrong. It's central notions are wrong on every front. The OoA is also wrong; but it's wrong in a way that means that a small refinement of the hypothesis explains the observed facts.
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Jon Inactive Member |
The lack of differences between populations, and our ability to flow genes between groups which are relatively isolated, means that it is extremely unlikely in our current situation that we'll see a split of humanity into two distinct species. Indeed; and I would say unlikely even in past times during which pre-sapiens made the transition to sapiens. We have yet to find any modern population of people that has been isolated long enough to speciate, and the on-off isolation offered by oscillating geographical and environmental factors does not seem to provide sufficient time for speciation. It seems reasonable that the factors that have allowed people the world over to maintain their identity as members of the same human speciesincluding and especially those natural ones from pre-technological and pre-exploration timeshave been in effect since the erectus expansion. That said, it appears far-fetched to believe there was a group isolated enough in whichapparently quite rapidlyspeciation could take place disconnected from other groups of the world population. Yet, this is precisely the model proposed by OOA. It is interesting, I think, to note that aside from this one astronomical exception to what we know of humanity, no other valid speciation has been demonstrated in the world population following the erectus expansion. The speciations that are proposed are all tenuous re-definitions of the word 'species', and are usually just arbitrary lines drawn around random or expected regional variations whose presence in one group but not in another can be easily explained without the 's-word' (for example, the stockier build of neanderthalensis simply doesn't work in hotter Asia and Africa, thus explaining its confinement). Anyway, this is a slightly different problem than the migration issues we've been discussing, and I think I've said enough on it to initiate some decent discussion. Jon Check out No webpage found at provided URL: Apollo's Temple! Ignorance is temporary; you should be able to overcome it. - nwr
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Taq Member Posts: 10085 Joined: Member Rating: 5.6 |
I speak English, but I'm not from England. How did European genes come to dominate the gene pool in North America, and why did the previous dominant indigenous DNA decline in number? Was it due to gene flow between static populations or was it due to migration? How would DNA that evolved on the open savannas of Africa come to dominate very different habitats? The MH theory would argue that African lineages would make up a much smaller proportion of local variation with locally evolved DNA being dominant. That is not what we see. We see something akin to the appearance of European DNA in North America.
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Jon Inactive Member |
Have you not been reading my last several posts? I think I've done a good job showing you that the types of evidence we would expect to see from a migration event are exactly the types of evidence that we do see. And, your response to that is a vague reference to an undefined "specific type of evidence" which you claim is lacking. This is highly rude and disingenuous debate style, Jon. Please put some effort into it. Until you start defining these vague things you're referring to, I don't see any reason to put any stock in any argument you've made. The mass movements and replacements exemplified by the American rush and westward expansion do leave certain types of evidence, evidence that is different than a slow expansion and/or hybridization model. One type of evidence such movements leave is signs of each group existing simultaneously and distinctly in serious geographical proximity followed by the existence of only one of the groups in the entire geographical zonei.e., at layers dating to t1 we have both groups existing near yet distinctly from one another, while layers dating to t2 show just one group existing in the entire region (the group that did the replacing). Finding such evidence would add much needed support to the extraordinary claims of OOA.
We do if that one population consists of about 1 million people spread out over a landmass that covers 1/6th of the planet's surface. Again, you make this claim about migrations being necessary, but you show no evidence to back it up. People all over the globe have been pretty good at maintaining their identity as members of the same human species in spite of the infrequency of such migrations. Yet, you argue that such a migration was the only way of keeping genetic material linked at this one point in the past, ignoring the fact that it has been for all other periods of the past one of a rare and non-essential methods of maintaining a single world species. What is so special about this one period that makes it impossible for the world members of a species to have remained connected without massive migrations outward from the centers of any slightly-beneficial genetic innovation?
We're not talking about novel genes, Jon! We're talking about entire genomes! Please assimilate this important detail! I am not sure I understand. As far as MH is concerned, there was no 'entire genome' (I assume you mean the aspects that differentiate sapiens and pre-sapiens) that spread from a point of origin; there were, instead, genetic innovations that spread individually from a point(s) of origin, which, when accumulated, represent an 'entire genome' that can be said to have evolved within an entire world population as the individual genetic innovations that make up that genome accumulated in all members of that world population.
... we're talking about entire genomes---non-coding DNA that is irrelevant to fitness included---saturating the global gene pool. Perhaps you could lay out the specific things you're referencing. As far as I am aware, genetic flow alone can spread both relevant and irrelevant traits alike.
But, it is a very lousy explanation for why Paleo-African alleles dominate every modern human genome that has ever been studied. Not when the 'Paleo-African' groups were the largest, most dense, and central groups of the world population. Then the dominance is entirely consistent and expected given either the MH or OOA model. Genetic traits of the central, large, denser groups of a population will naturally dominate the population as a whole whether through hybridization or OOA-type migration. Dominance of African alleles does not necessarily support the OOA model anymore than it supports an alternative model.
What specific types of movements? I have challenged your assertion that OOA is formulated around a specific type of movement, and you just keep re-asserting it. And, I can't resist pointing out that the "expected behavior" of nomadic peoples is migration. That's pretty much the definition of "nomad." Yes, circular migrations, where populations move through ancestral routes with the changing of the seasons and harvest times, returning to their points of origin at the end. This is different from the move-and-stay migration (such as the American expansion westward discussed earlier) proposed by OOA. We call them both 'migration', but they are not the same thing; to argue that OOA is accurate in proposing migration type 2 because all nomadic, hunter-gatherer populations (the only type existing at the time) exhibit migration type 1 is an equivocation and does not support the migration models of OOA. Jon Check out No webpage found at provided URL: Apollo's Temple! Ignorance is temporary; you should be able to overcome it. - nwr
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Jon Inactive Member |
The MH theory would argue that African lineages would make up a much smaller proportion of local variation with locally evolved DNA being dominant. No, it would not. The dominance of African traits in the human population is perfectly consistent with MH. See my post to Bluejay above about the importance of population densities. Jon Check out No webpage found at provided URL: Apollo's Temple! Ignorance is temporary; you should be able to overcome it. - nwr
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Nuggin Member (Idle past 2523 days) Posts: 2965 From: Los Angeles, CA USA Joined: |
That said, it appears far-fetched to believe there was a group isolated enough in whichapparently quite rapidlyspeciation could take place disconnected from other groups of the world population. I dunno. I suspect that Flores was actually isolated enough for no gene flow. It's features are really early homonid compared to later groups.
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Nuggin Member (Idle past 2523 days) Posts: 2965 From: Los Angeles, CA USA Joined: |
I don't agree that it's clearly both. Even with the new evidence, the MR is still wrong. It's central notions are wrong on every front. Depends on what you mean by MR. If you are saying MR is Erectus etc populations evolved in isolation from one another to create Asians, Africans, Europeans - then yeah, that's wrong. However, if you are saying that genes developed in isolated homonid groups and that those genes appear in current human populations as a result of gene flow into the group that left Africa - that's right. All groups outside of Africa have the Neanderthal genes. So clearly a group left Africa (OoA) and picked up some genes from other groups (MR) along the way.
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Blue Jay Member (Idle past 2728 days) Posts: 2843 From: You couldn't pronounce it with your mouthparts Joined: |
Hi, Nuggin.
I promised to leave, but I can't stay away.
Nuggin writes: So clearly a group left Africa (OoA) and picked up some genes from other groups (MR) along the way. We're talking about something like 5% of the mutations in one insular population of modern humans being Denisovan, though (along with 1-4% of most of the world's mutations being Neanderthal). How small does the contribution of non-sapiens have to be before we consider MR effectively refuted? It doesn't seem all that meaningful to acknowledge a theory that only explains such a tiny percentage of the data. It's like calling a sports game a draw because both teams scored points. -Bluejay (a.k.a. Mantis, Thylacosmilus) Darwin loves you.
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Nuggin Member (Idle past 2523 days) Posts: 2965 From: Los Angeles, CA USA Joined: |
We're talking about something like 5% of the mutations in one insular population of modern humans being Denisovan, though (along with 1-4% of most of the world's mutations being Neanderthal). How small does the contribution of non-sapiens have to be before we consider MR effectively refuted? So the problem here is one of principles. One group is saying that if _any_ contribution was made then an OoA claim is refuted because clearly not all the genes came from Africa. One group is saying that the genes contributed by MR groups are small or insignificant in number, therefore they should be ignored. The truth is that a wave of people whose offspring represent the vast majority of genetic survivors left Africa to sweep across a world where other human groups already existed. Along the way, that wave absorbed and/or replaced those existing groups, picking up some additional genes which were not present in the initial wave. It's not 100% OoA, it's not 100% MR. they both factor into the real events. Yes, OoA is more influential. I agree. But, existing populations did contribute as well.
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jar Member (Idle past 425 days) Posts: 34026 From: Texas!! Joined: |
How did the existing populations get there?
Anyone so limited that they can only spell a word one way is severely handicapped!
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Nuggin Member (Idle past 2523 days) Posts: 2965 From: Los Angeles, CA USA Joined: |
How did the existing populations get there? That's what I was saying a few posts back. If you want to move back the line for what homonids you are talking about, then you change the discussion. If we're talking strictly modern homo sapiens, then it's OoA.If we're talking about homo sapiens and groups they can exchange genes with, then it's both If we're talking about H. Erectus only and how it got to Java etc, then it's probably OoA, however Flores makes it unclear. If we're talking about whatever population founded Flores, then we're back to OoA. If we're talking about anything from the genus homo, then it's back to OoA. If we're talking anything mammal, then maybe it's NOT OoA, whatever landmass first hosted mammals. You can move the line anywhere you want and change the rules for the discussion. Unless people are able to agree where the line is set, then discussion is useless. We might as well be saying "The week begins on Sunday" or "The week begins on Monday". It depends on who you ask and what they mean by "week".
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Jon Inactive Member |
You can move the line anywhere you want and change the rules for the discussion. Unless people are able to agree where the line is set, then discussion is useless. I don't think that that's been happening in this debate. We may disagree on whether certain varieties can be classified as different species, but that is beside the point being discussed. The main theme here is the origin of a particular variety and how that variety came to dominate, regardless of how we wish to classify that variety in relation to other varieties. Jon Check out No webpage found at provided URL: Apollo's Temple! Ignorance is temporary; you should be able to overcome it. - nwr
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Nuggin Member (Idle past 2523 days) Posts: 2965 From: Los Angeles, CA USA Joined: |
I don't think that that's been happening in this debate. We may disagree on whether certain varieties can be classified as different species, but that is beside the point being discussed. The main theme here is the origin of a particular variety and how that variety came to dominate, regardless of how we wish to classify that variety in relation to other varieties. Well, that's not much of a debate. Clearly all the populations outside of Africa arose from a very limited number of mDNA sources, back tracking location and dating demonstrates the OoA.
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Jon Inactive Member |
Clearly all the populations outside of Africa arose from a very limited number of mDNA sources, back tracking location and dating demonstrates the OoA. Perhaps genetically, yes. But no one has yet disagreed with the genetic evidence; its interpretation is what is at issue here. Jon Check out No webpage found at provided URL: Apollo's Temple! Ignorance is temporary; you should be able to overcome it. - nwr
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