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Author Topic:   Neandertal Place in Human Origins
Apostle
Inactive Member


Message 1 of 7 (77266)
01-09-2004 12:43 AM


This is an excerpt from a paper I recently wrote on Neandertals. It is only a rough draft, so please take the opportunity to point out any flaws or information errors. I would also be interested as to whether the majority of evolutionists side with the single-origin or the multiorigin model. (This was pasted over from notepad so please forgive any formatting errors, particularly species names not being italicized".

"C. Neandertals Place in Human Origins

Two major hypotheses have arisen in an attempt to answer where different finds fit into the history of human origins. The Neandertal has also been incorporated into these theories, though the debate as to which is more accurate is far from over.

1. The Multiregional Model

According to this hypotheses, Homo sapiens developed from populations of Homo erectus in many different areas across the globe. These transformations occured in all populations of H erectus wherever they existed. Such transformations led to a near simultaneous appearance of multiple populations of modern humans across Africa and Europe. This human evolution was shaped by gene flow, natural selection and genetic drift. Gene flow is credited with preventing populations of H erectus from radiating into several different species. Hence, in between H sapien and H erectus are some archaic humans that are difficult to place because of their perceived intermediate appearance. Such a view was first proposed in detail by Gustav Schwalbe who argued that there was an evolutionary sequence which began with Pithecanthropus, led to Neandertal and continued on to modern human.
Fifty years ago, Franz Weidenreich proposed a potentially dangerous concept. Weidenreich suggested that such a transition from H erectus to H sapien, occured in a parallel fashion in various regions of the world. ( Such a notion might give rise to the belief that if in each part of the world there is a seperate transition from H erectus to H sapien, perhaps the transition is slower in some areas. Under such circumstances, certain races would be viewed as more evolved than others giving rise to racist additude among some, and scientific justifiability to other extremists, some of whom may wield power. Such circumstances would not be unlike the persecution of the Jews by Hitler who held that they were the most inferior race.). In 1942, Weidenreich clearly stated that it was not his view that modern humans had seperate origins or that they were a seperate species. Despite Weidenreich distancing himself from such a belief, University of Pennsylvania anthropologist Carelton Coon came eerily close to embracing what Weidenreich had warned against. In 1962, Coon argued that racial differences were ancient and that some races had acheived their sapienhood earlier than others. (Such a view is incredibly dangerous, as I have already written). For a very brief time (just under two years) Coon's view was accepted enough that it became too difficult to place for some believed the Neandertal to be an extinct side branch while other believed that the Neandertal of Western Europe was the evolutionary product of the less extreme and distorted forms that have been found through the Middle East and Eastern Europe, which gave rise to modern humans. Two years past, and in 1964, University of Michagan professor Loren Brace argued that Neandertal anatomy had been mistakenly interpreted as extreme and that it could actually be seen as ancestral to the of later European modern people. Brace's view restored Neandertal's to where they were before Weidenreich and more particularly, Coon.

2. The Single Origin Model

This notion states that a population of the modern form of H sapiens arose in Africa at an early date and spread rapidly across Asia and Europe. The modern form is referred to as Homo sapiens sapiens which enables researchers to distinguish it from other archaic forms. It refers to the subspecies H sapiens which includes both modern and archaic forms.

Under the single origin moder many archaic forms of H sapiens that have been found in Asia or Europe are believed to have evolved into H Erectus, but not necessarily into H sapiens sapiens. Being one of the more well known archaic forms, Homo sapiens neandertalensis, believed to have lived between 130 000 and 35 000 years ago, was at one point considered a direct ancestor to modern humans. It is now generally accepted among scientists, based on fossil finds, that modern humans did not evolve from populations of Neandertals.

Where does that leave the Neandertal? Experts for over a certury have asked and sought out whether modern europeans carry some of the same genes that gave life to the Neandertal man. An answer could determine whether or not modern europeans are descendants of the Neandertal as the multiregionalits would argue. In an incredible feat, researchers at the University of Munich were able to cut away a small piece of a Neandertal's right upper arm bone. Led by Svante Paablo, the researchers extracted a small amount of DNA from the Neandertal's bone and then compared it with modern genes. The result: The Neandertal DNA was substantially different from the DNA of modern humans. This was enough to rule out the possibility that they were our ancestors. Paablo concluded that his find suggests "that Neandertals were extinct without contributing mitochondrial DNA to modern humans."
Such a discovery did not destroy the multiregional belief, for the multiregional model made a significant comeback when in Israel ( the Kebara Cave, Mount Carmel, and Amud near the sea of Galilee) Neandertals were discovered. This in itself was not grounbreaking. What was though was that they were found to be approximately 60 000 years old while the modern forms nearby were 40 000 years old. Assuming these dates are correct this presents a perfect time progression from the Neandertal to the modern form.

Given the newer dating methods, electronic spin resonance, and thermoluninesence, some skeletons were found to have lived 100 000 years ago. The Neandertal's in Tabun, Israel were slightly older, which does allow for the possibility of an ancestor/descendant relationship. That some modern forms are older than Neandertal's is not relevant because those who hold to the multiregionalist view, make no distinction between individuals, for they feel that all members of an anatomically variable population. Some, like Roger Lewin, have dismissed this as special pleading, for such a view would require a variability unknown in any other human populations. If the Neandertal simply became extinct then he should be placed under the name Homo Neandertalensis as Irish anatomist William King first proposed in 1864."

Apostle

[This message has been edited by Apostle, 01-09-2004]


Replies to this message:
 Message 2 by Mammuthus, posted 01-09-2004 2:57 AM Apostle has not replied
 Message 3 by sfs, posted 01-09-2004 11:47 AM Apostle has not replied
 Message 4 by PaulK, posted 01-09-2004 11:59 AM Apostle has not replied

  
Mammuthus
Member (Idle past 5794 days)
Posts: 3085
From: Munich, Germany
Joined: 08-09-2002


Message 2 of 7 (77277)
01-09-2004 2:57 AM
Reply to: Message 1 by Apostle
01-09-2004 12:43 AM


While not addressing the multiregional versus single origin debate, I would point out that subsequent to Krings et al work on the neandertal type specimen, a few more neandertal sequences have been obtained that confirm the results of the initial find

Krings M, Capelli C, Tschentscher F, Geisert H, Meyer S, von Haeseler A, Grossschmidt K, Possnert G, Paunovic M, Paabo S. A view of Neandertal genetic diversity.
Nat Genet. 2000 Oct;26(2):144-6.

Ovchinnikov IV, Gotherstrom A, Romanova GP, Kharitonov VM, Liden K, Goodwin W.
Molecular analysis of Neanderthal DNA from the northern Caucasus.
Nature. 2000 Mar 30;404(6777):490-3.


This message is a reply to:
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sfs
Member (Idle past 1853 days)
Posts: 464
From: Cambridge, MA USA
Joined: 08-27-2003


Message 3 of 7 (77329)
01-09-2004 11:47 AM
Reply to: Message 1 by Apostle
01-09-2004 12:43 AM


quote:
The result: The Neandertal DNA was substantially different from the DNA of modern humans. This was enough to rule out the possibility that they were our ancestors. Paablo concluded that his find suggests "that Neandertals were extinct without contributing mitochondrial DNA to modern humans."

You and Paabo are saying different things here. Of the two statements, Paabo's is the more limited, and the more correct. The mtDNA results show that Europeans did not inherit any mitochondrial DNA from Neanderthals. That makes it quite unlikely that they made a major contribution to our genes, but it does not rule out the possibility that there was some Neanderthal contribution to European genes in other parts of the genome. Studies of nuclear loci confirm the view that most non-African genes had a recent African origin, but they do not offer a conclusive answer to the question of whether the contribution from non-African archaics was small or actually zero.

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PaulK
Member
Posts: 17179
Joined: 01-10-2003


Message 4 of 7 (77333)
01-09-2004 11:59 AM
Reply to: Message 1 by Apostle
01-09-2004 12:43 AM


It seems to me that the actual discussion is mainly about the multi-regional versus the out-of-Africa models rather than about the Neandertals. Either model is compatible with the Neandertals as a subspecies of Homo Sapiens or as a closely related species.

To the best of my knowledge out-of-Africa is by far the dominant model.

While I don't have time to track it down, IIRC there are a few remains that have been identified - perhaps incorrectly - as hybrids between Neandertals and fully modern humans. I would suggest that they would be more important to the question of the position of Neandetals than the multiregional vs out-of-Africa question.


This message is a reply to:
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Trixie
Member (Idle past 3025 days)
Posts: 1011
From: Edinburgh
Joined: 01-03-2004


Message 5 of 7 (77822)
01-11-2004 4:07 PM


Hold on, you lot!!!!!
I think I might be a bit behind the times here, or ahead, I don't know which. I thought that recent research had decided that modern humans didn't descend from Neandertals, but had descended from Cro-Magnons. For example, Cheddar man has Cro-Magnon mtDNA, not Neandertal. I'm going on the work of Prof Brian Sykes and his mtDNA analyses of modern and ancient man. Furthermore the evidence seems to point to Neandertals and Cro-Magnons existing in the same time period 34-36000 years ago with the question of whether they ever interbred. The bottom line was that basically Neandertals died out as Cro-Magnons became more numerous. The mtDNA analysis suggested that Cro-Magnons came out of Africa in the same way that Neandertals did, but later and although they ovelapped a bit, they were distinct. Also a find last summer in Portugal has thrown up the possibility that Neandertals and Cro-Magnon may occassionally bred. The find is that of a child's skeleton and is dated to 34-36000years ago, during the overlap and certain features seem to be Neandertal and certain others seem to be Cro-Magnon

Now, have I missed something that's happened to totally contradict this Cro-Magnon theory and completely invalidate the mtDNA analyses on which this theory is based? Please help, because I'm getting really confused!!!


Replies to this message:
 Message 6 by PaulK, posted 01-11-2004 4:24 PM Trixie has replied

  
PaulK
Member
Posts: 17179
Joined: 01-10-2003


Message 6 of 7 (77825)
01-11-2004 4:24 PM
Reply to: Message 5 by Trixie
01-11-2004 4:07 PM


Re: Hold on, you lot!!!!!
I think most of what you say is pretty much correct.

One little point to remember is the "Cro Magnons" are fully modern humans. In that sense they are "us".

Now if there was interbreeding between fully modern humans and Neandertals then that would tend to support the view that Neandertals should be classified as a subspecies (interfertility is an important consideration in such comparisons even if it is not the only consideration). That does not invalidate the DNA analysis, it is just another factor to consider when making a decision on the taxonomic classification.

I seem to remember some criticisms of the methodology of the mitochondrial DNA studies on this forum. Does anyone else remember any more details ?


This message is a reply to:
 Message 5 by Trixie, posted 01-11-2004 4:07 PM Trixie has replied

Replies to this message:
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Trixie
Member (Idle past 3025 days)
Posts: 1011
From: Edinburgh
Joined: 01-03-2004


Message 7 of 7 (77845)
01-11-2004 5:39 PM
Reply to: Message 6 by PaulK
01-11-2004 4:24 PM


Re: Hold on, you lot!!!!!
Thank you for your reply. Must admit I was worried for a minute. I'd just got my head round the whole Cro-Magnon business, then I see the above talking about descent from Neandertals.

I would be interested in any info anyone has on criticism of the mtDNA methodology used. I know at one point that evidence was put forward suggesting that recombination may have occurred ie that somehow mtDNA from the father's sperm could have gained access to the innards of the egg and thus changes in the mtDNA would not necessarily represent a mutation, but a huge recombination event, thus destroying the "timeline" used to determinehow long base changes took to occur randomly, without external input. I also know that 18 months after this was published, the authors retracted, having misread the data coming off their automated sequencer - they had claimed that they had found mutations at a position in the seventies of the sequence which proved recombination, but actually it was a mutation in the eighties which was already accounted for.

I'm really interested in this and have been busily downloading primer sequences for the amplification of mtDNA and known sequences of the 500bpr fragment that they use in their analysis (in the vain hope that I might just find the time to do my own mtDNA). I would hate to think that all my hard graft during the Christmas holidays had been a waste of time. I really must get out more!!


This message is a reply to:
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