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Author | Topic: New Type of Ancient Human Found—Descendants Live Today? | |||||||||||||||||||||||
ramoss Member (Idle past 632 days) Posts: 3228 Joined: |
http://news.nationalgeographic.com/...volution-fossil-finger
A previously unknown kind of humanthe Denisovanslikely roamed Asia for thousands of years, probably interbreeding occasionally with humans like you and me, according to a new genetic study. In fact, living Pacific islanders in Papua New Guinea may be distant descendants of these prehistoric pairings, according to new analysis of DNA from a girl's 40,000-year-old pinkie bone, found in Siberian Russia's Denisova cave. This "new twist" in human evolution adds substantial new evidence that different types of humansso-called modern humans and Neanderthals, modern humans and Denisovans, and perhaps even Denisovans and Neanderthalsmated and bore offspring, experts say. "We don't think the Denisovans went to Papua New Guinea," located at the northwestern edge of the Pacific region called Melanesia, explained study co-author Bence Viola, an anthropologist at the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany. "We think the Denisovan population inhabited most of eastern Eurasia in the same way that Neanderthals inhabited most of western Eurasia," Viola said. "Our idea is that the ancestors of Melanesians met the Denisovans in Southeast Asia and interbred, and the ancestors of Melanesians then moved on to Papua New Guinea." (See "Interspecies Sex: Evolution's Hidden Secret?") Interbreeding Common Among Various Types of Humans? Taken together with a May DNA study that found Neanderthals also interbred with modern human ancestors, the Denisovan finding suggests there was much more interbreeding among different human types than previously thought, Stanford University geneticist Brenna Henn said. "In the actual archaeological record, people have been talking about this for a long time ... But before six months ago, there was no genetic evidence for any admixture between archaic humans and modern humans," said Henn, who co-authored an article accompanying the study in tomorrow's issue of the journal Nature. "Then these two papers come out, and I won't say they've turned the field on its head, but they certainly support a view that has not been well recognized for years" by geneticists, said Henn, who wasn't part of the study. Brian Richmond, a paleoanthropologist at George Washington University, said he expects the new study to spark much interest and excitement. "Nothing is more intriguing than learning new twists about our origins," said Richmond, who also didn't participate in the Denisovan-genetics research. "And this is another new twist." Fossil Finger Points to New Human Type The centerpiece of the DNA study is a Denisovan fossil finger bone discovered in 2008. The fossil is thought to be from a young girldubbed X-womanwho was 5 and 7 years old when she died. For a previous Nature study, released in March 2010, the team had collected and sequenced mitochondrial DNA, or mtDNA, from X-woman's finger. But mtDNAinherited only from motherscontains far less information about a person's genetic makeup than DNA found in the nucleus of a cell, or nuclear DNA (quick genetics overview). In the new study the team reports successfully extracting and sequencing so-called nuclear DNA from the bone. Then, using DNA-comparison techniques, the scientists were able to determine that Denisovans were distinct from both modern humans and Neanderthals, yet closely related to the latter. The team estimates Denisovans split from the parent group of Neanderthals about 350,000 years ago.
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Coyote Member (Idle past 2126 days) Posts: 6117 Joined: |
The Max Planck folks are about the best around for analyzing ancient DNA, but I would love to see a couple of additional specimens sequenced and see if the results match.
This finding, if confirmed, would add support to the multiregional theory. Religious belief does not constitute scientific evidence, nor does it convey scientific knowledge.
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Omnivorous Member Posts: 3983 From: Adirondackia Joined: Member Rating: 7.0 |
I have more interest in than understanding of the multiregional vs. out of Africa debate. Could you explain why you see these results as supporting the multiregional hypothesis?
To my untrained mental eye, it looks as though you could interpret the findings as evidence that H. sapiens migrating from Africa pushed Neanderthals and their Denisovan cousins to "the ends of the earth". I thought the multiregional explanation was the descent of modern Europeans from Neanderthals--perhaps I'm badly outdated, or simply wrong in that understanding? I know there's a balance, I see it when I swing past. -J. Mellencamp Real things always push back.-William James
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Coyote Member (Idle past 2126 days) Posts: 6117 Joined: |
I have more interest in than understanding of the multiregional vs. out of Africa debate. Could you explain why you see these results as supporting the multiregional hypothesis? To my untrained mental eye, it looks as though you could interpret the findings as evidence that H. sapiens migrating from Africa pushed Neanderthals and their Denisovan cousins to "the ends of the earth". I thought the multiregional explanation was the descent of modern Europeans from Neanderthals--perhaps I'm badly outdated, or simply wrong in that understanding? The multiregional hypothesis seems to be incorrect for the west, Africa and Europe, but I wonder if these findings may not support it for eastern Asia. I have always wondered about some line traits from Asian erectus that seem to persist into modern Asian groups. The finding that there was an additional, previously unknown species in east Asia and that it has some living descendants just adds to the problem--and the question of just how much interbreeding was going on that has not previously been recognized. From the article:On the basis of the new findings, the scientists propose that the ancestors of Neanderthals and Denisovans emerged from Africa half a million years ago. The Neanderthals spread westward, settling in the Near East and Europe. The Denisovans headed east. Some 50,000 years ago, they interbred with humans expanding from Africa along the coast of South Asia, bequeathing some of their DNA to them. ... Given the DNA showing up in New Guinea and Bougainville, there does seem to have been interbreeding. Now the question is among whom, and how much? But given the persistence of this new DNA in Asia from 400,000 or 500,000 years ago to modern humans, there seems to be some support for the multiregion hypothesis in eastern or southeastern Asia. Add: From another article: Paabo says the DNA they already have does indicate that this Siberian stranger, along with humans and Neanderthals, evolved from some common ancestor that lived in Africa about a million years ago. "Whoever carried this mitochondrial genome out of Africa about a million years ago is some new creature that has not been on our radar screens so far," he says. Edited by Coyote, : Added information Edited by Coyote, : Add link
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Omnivorous Member Posts: 3983 From: Adirondackia Joined: Member Rating: 7.0 |
Thanks, Coyote. The link you added was useful. I'm doing a bit of background reading now about the history of the dispute.
Do you suppose migrations of H. sapiens into those areas were more likely to result in interbreeding rather than displacement of the older population because the earlier migrations were too well established to just push out of the way? I know the Neanderthal were physically robust, but I've somehow gathered the impression that their population sizes were not. I read through David Johanson's summary at Action Bioscience. It is a popular account, somewhat dated, I suppose, since it's copyrighted 2001, but it has been useful to me in understanding the history. He notes:
quote: Is the arrival of modern humans there at 50,000 y.a. really a problem for multiregional advocates? Their hypothesis explicitly describes interbreeding/gene flow, right? Have those Chinese skulls (or subsequent finds) panned out? I know there's a balance, I see it when I swing past. -J. Mellencamp Real things always push back.-William James
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Coyote Member (Idle past 2126 days) Posts: 6117 Joined: |
I haven't kept up with the really technical details since grad school.
My bet though is that there was some continuity in Asia, and it most likely took the form of interbreeding. Modern humans certainly took over pretty well when they arrived, but I think they swamped out some of the earlier groups through interbreeding, rather than elimination and replacement. This most recent DNA evidence seems to suggest that. But I'd like to see it confirmed with a couple of additional sequences before I bet the rent money on it.
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Omnivorous Member Posts: 3983 From: Adirondackia Joined: Member Rating: 7.0 |
Coyote writes: My bet though is that there was some continuity in Asia, and it most likely took the form of interbreeding. I felt vindicated when more recent DNA studies contradicted the early mitochondrial results and suggested some interbreeding between modern and Neanderthal populations. I always found it difficult to believe that every H. sapiens male passed up every opportunity to mate with a Neanderthal, even if they were short, strong and chinless. I mean, I've been in Asian bars at closing time... I know there's a balance, I see it when I swing past. -J. Mellencamp Real things always push back.-William James
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Dr Jack Member Posts: 3514 From: Immigrant in the land of Deutsch Joined: Member Rating: 8.3 |
This finding, if confirmed, would add support to the multiregional theory. It seems to me that this is closer to a refinement of the Out-Of-Africa hypothesis than support for the multiregional hypothesis, we're still looking at a single main H. sapeins that emerged from Africa, just now with some slight admixture from other Homo species (or subspecies?). The multiregional hypothesis held that there were distinct mainlines in different regions; this remains clearly wrong.
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Percy Member Posts: 22479 From: New Hampshire Joined: Member Rating: 4.7 |
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Jon Inactive Member |
The multiregional hypothesis held that there were distinct mainlines in different regions; this remains clearly wrong. No; it didn't. The key to MH is that it supposes the regional populations remained genetically linked to one another and so evolved as something of a single 'world population'. If so, we should find some regional genetic links between past homo varieties and modern h. sapiens native to those same regions. That is why this finding adds support to MH, since it shows that past and present homo varieties were not only capable of breeding, but did breed. The one-off African origin (of h. sapiens) proposed by OOA is simply not adequate for explaining this continuation of regional variations into present human linesat least some aspects of modern humanity must have evolved outside of Africa prior to 50-60 kya. Jon Edited by Jon, : Clarifications 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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Dr Jack Member Posts: 3514 From: Immigrant in the land of Deutsch Joined: Member Rating: 8.3 |
The multiregional hypothesis supposes that each local population evolves in parallel, with gene flow between populations maintaining the various populations. That's radically different from the situation found by this (and other recent) research.
see this picture The one-off African origin (of h. sapiens) proposed by OOA is simply not adequate for explaining this continuation of regional variations into present human linesat least some aspects of modern humanity must have evolved outside of Africa prior to 50-60 kya. Yes, but we're talking less than 10% of the genome. We're still talking about a species that evolves in Africa spreading through the world, and replacing existing populations. That there was a small degree of gene flow from those populations alters that details of that picture but it doesn't change the overall narrative. According to this research, H. sapiens evolved in Africa and spread to melanasia. Once there there was a small degree of interbreeding. That still Out of Africa.
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Jon Inactive Member |
We're still talking about a species that evolves in Africa spreading through the world, and replacing existing populations. The replacement model is simply not accurate. This finding supports the notion that h. sapiens mixed with the earlier populations rather than merely replaced them. This is something predicted by MH; OOA proponents, on the other hand, have not been able to make these predictions, and have resorted to constant alterations of their model to explain new and contradictory evidencein similar fashion to the epicycles of geocentrism. Jon Edited by Jon, : clarity 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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Omnivorous Member Posts: 3983 From: Adirondackia Joined: Member Rating: 7.0 |
Hi, Jon.
I want to make sure I understand what formulation of the multiregional hypothesis you embrace and consider evidenced by this new data. Here's a summary of the debate by David Johanson:
quote: Do you agree with his description of the competing hypotheses? I know there's a balance, I see it when I swing past. -J. Mellencamp Real things always push back.-William James
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Jon Inactive Member |
That seems to be a pretty reasonable summary, yes. There are other things that I'd argue to be true about the relation of h. sapiens to critters like erectus and such, but I don't believe those things to be a necessary part of the usual MH description.
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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anglagard Member (Idle past 856 days) Posts: 2339 From: Socorro, New Mexico USA Joined: |
Omnivorous writes: Here's a summary of the debate by David Johanson: Please note I am quoting Johanson through Omnivorius' post. The Multiregional Hypothesis:
some level of gene flow between geographically separated populations prevented speciation after the dispersal Seems reasonable, particularly considering recent findings.
all living humans derive from the species Homo erectus that left Africa nearly two million-years-ago Seems unreasonable, particularly considering recent findings.
natural selection in regional populations, ever since their original dispersal, is responsible for the regional variants (sometimes called races) we see today As Damon Wayans when playing the clown from In Living Color would say "homie don't think so" right before he clubbed someone over the head. Recent DNA evidence indicates all are essentially modern Homo Sapiens, with a slight bit of spice from Neanderthals and/or Denisovans.
the emergence of Homo sapiens was not restricted to any one area, but was a phenomenon that occurred throughout the entire geographic range where humans lived Doubtful, smells like appeal to magic. Now for the converse:
In contrast, the Out of Africa Model asserts that modern humans evolved relatively recently in Africa, migrated into Eurasia and replaced all populations which had descended from Homo erectus. Critical to this model are the following tenets: homo sapiens arose in Africa and migrated to other parts of the world to replace other hominid species, including homo erectus; Homo Erectus appears to be more a cousin than a direct ancestor according to the most modern interpretations of physical anthropology, in accordance with actual physical measurements of the fossils.
after Homo erectus migrated out of Africa the different populations became reproductively isolated, evolving independently, and in some cases like the Neanderthals, into separate species Guess we will have to wait for some shred of DNA from Homo Erectus to make this one work out. In the meantime it appears both Homo Sapiens and Neanderthals evolved from Homo Rhodesiensis, rather than Homo Erectus.
Homo sapiens arose in one place, probably Africa (geographically this includes the Middle East) This hypothesis would, of course, fit in with the evolution of any other critter, be it observed or evidenced by the scanty fossil record.
Homo sapiens ultimately migrated out of Africa and replaced all other human populations, without interbreeding Oops, the most recent DNA evidence indicates their was some slight inbreeding between modern Homo Sapiens, Neanderthals and the more recently speculated Denisovans.
modern human variation is a relatively recent phenomenon Almost entirely, except for that lil' bit of DNA evidence. I think the 'Out of Africa' hypothesis is mostly correct except for that smidgen of DNA from our distant cousins, none of which has been shown to be from erectus. One reason I see slight interbreeding is due to that old saying from New Mexico Tech "Socorro, where women are men and sheep are restless." Reality is always more complex than a slogan. The idea of the sacred is quite simply one of the most conservative notions in any culture, because it seeks to turn other ideas - uncertainty, progress, change - into crimes. Salman Rushdie This rudderless world is not shaped by vague metaphysical forces. It is not God who kills the children. Not fate that butchers them or destiny that feeds them to the dogs. It’s us. Only us. - the character Rorschach in Watchmen
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