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Author Topic:   Neanderthals
Mammuthus
Member (Idle past 6475 days)
Posts: 3085
From: Munich, Germany
Joined: 08-09-2002


Message 121 of 159 (60506)
10-11-2003 8:23 AM
Reply to: Message 120 by sfs
10-11-2003 12:42 AM


Hi sfs,
I completely agree with your assessment. And I personally don't care whether multi-regionalism or out of Africa is correct or whether or not neandertals and H. sapiens interbred. But I do object to Paabo and Cooper's attack on the cro magnon work as being a contaminant since it is identical to modern human and their suggestion that only divergent sequences can be accepted. That is just not good science. If it really is a technical limitation then at this current juncture, studies of ancient human remains just should not be done . Otherwise no conclusions about human evolution can be drawn at all. My opinion is that this is exactly the stage aDNA is at....another reason why I work on mammoths and ancient muskoxen...pretty easy to identify human contamination
I am also horrible at remembering names unless they are amusing....like the sales rep I met whose last name was Fartmann...

This message is a reply to:
 Message 120 by sfs, posted 10-11-2003 12:42 AM sfs has replied

Replies to this message:
 Message 122 by BellaSanta, posted 10-11-2003 11:06 AM Mammuthus has not replied
 Message 123 by NosyNed, posted 10-11-2003 12:28 PM Mammuthus has replied
 Message 134 by sfs, posted 10-13-2003 9:57 PM Mammuthus has not replied

  
BellaSanta
Inactive Member


Message 122 of 159 (60516)
10-11-2003 11:06 AM
Reply to: Message 121 by Mammuthus
10-11-2003 8:23 AM


wow, this topic sure is jumping around!
MMmmmmm I am not sure what to address first. I think at the moment technology is advancing too fast for scientists to successfully use it properly, either that or they are incorrect in their interpretations of the data presented to them [you only have to look at the mDNA testing done and the differing interpretations]. There is a poster at my university that says "If we are to understand the present we must first understand the past".
It is my understanding that H. erectus was the first species to migrate out of Africa, that they managed to superceed existing hominid species and evolve (?). Anyway - I haven't done much study on Neandertals. But I do know that many features in H. erectus can still be seen in African tribes today, that 'archaic' modern human traits can be seen in modern Asian populations also. Perhaps, even though Neandertals showed signs of progressing forward they were too slow (?), were bred out of existance(?) - who knows.
Keep safe
Bella

This message is a reply to:
 Message 121 by Mammuthus, posted 10-11-2003 8:23 AM Mammuthus has not replied

  
NosyNed
Member
Posts: 8996
From: Canada
Joined: 04-04-2003


Message 123 of 159 (60520)
10-11-2003 12:28 PM
Reply to: Message 121 by Mammuthus
10-11-2003 8:23 AM


Why is an issue about the contaminents?
I think we can assume that neanderthals and us share a lot of genes. So if sequence them we will find similar genes for that reason as well as possible contaminents.
So we ignore the similarities. We do find differences. Differences that are taken as big enough to suggest we have not interbred.
If we counted as the similarities as real neanderthal dna would the conclusion be any different?

This message is a reply to:
 Message 121 by Mammuthus, posted 10-11-2003 8:23 AM Mammuthus has replied

Replies to this message:
 Message 124 by Mammuthus, posted 10-11-2003 2:25 PM NosyNed has replied

  
Mammuthus
Member (Idle past 6475 days)
Posts: 3085
From: Munich, Germany
Joined: 08-09-2002


Message 124 of 159 (60526)
10-11-2003 2:25 PM
Reply to: Message 123 by NosyNed
10-11-2003 12:28 PM


The issue is in distinguishing a sequence that is endogenous to the bone from one or many which come from environmental contamination say, the curator who touched the bone. Over time DNA degrades once the organism is dead so that after thousands of years (if there is any DNA left) there are many times as much DNA in the skin cells you shed doing the experiment than remain in the bone. In addition, the contaminating DNA will always be in better shape than ancient DNA. So, you extract DNA from a neandertal, all controls are clean, and the sequence falls right in the middle of the range of modern human...Paabo and Cooper scream contamination and discount the data. That is what they did with cro magnon which fell exactly in the middle of human mtDNA diversity (well for europe at least). Paabo and Cooper, and others then go on to claim that neandertals were genetidfcally divergent from modern humans and no cro magnon sequences that are acceptable exist. If you cannot accept sequences that look like modern then any "accepted" sequence will a priori have to be divergent and a priori assumes the conclusion that we are different. This is not scientific. Accepting the data that supports your pet hypothesis and ignoring or claiming any data that goes against it is invalid is what creationists do.

This message is a reply to:
 Message 123 by NosyNed, posted 10-11-2003 12:28 PM NosyNed has replied

Replies to this message:
 Message 125 by NosyNed, posted 10-11-2003 2:38 PM Mammuthus has replied
 Message 126 by Speel-yi, posted 10-12-2003 3:36 AM Mammuthus has replied

  
NosyNed
Member
Posts: 8996
From: Canada
Joined: 04-04-2003


Message 125 of 159 (60528)
10-11-2003 2:38 PM
Reply to: Message 124 by Mammuthus
10-11-2003 2:25 PM


I still don't quite get it. What about the divergent DNA? Isn't it different enough to both not come from contamination and to separate us from the neanderthals?
Or is that whole samples are rejected and there is the possibility of some heanderthals not being all tha divergent?

This message is a reply to:
 Message 124 by Mammuthus, posted 10-11-2003 2:25 PM Mammuthus has replied

Replies to this message:
 Message 127 by Speel-yi, posted 10-12-2003 3:58 AM NosyNed has not replied
 Message 128 by Mammuthus, posted 10-12-2003 8:50 AM NosyNed has not replied

  
Speel-yi
Inactive Member


Message 126 of 159 (60593)
10-12-2003 3:36 AM
Reply to: Message 124 by Mammuthus
10-11-2003 2:25 PM


I think a lot of this stems from the backlash against the old Out of Europe hypothesis that had people rejecting some of Darts early finds in Africa.
I also see this type of behavior with archeological finds in America. Not 40 miles from where I sit, there's a mammoth kill site that shows some pretty decent evidence of human occupation. The only problem is that the first radio-carbon dating came back with a date of 19,000 BP, it was then rejected as an archeological site because anything older than 12,000 BP can't have shown signs of human occupation since everyone knows that humans were not here until 12,000 BP.
Another persistant notion is the idea of replacement of old populations with new ones of the same species. The idea that humans exterminate each other is a tough one to eliminate from modern scientists minds. We see the same thing with the Spirit Cave Man and Kennewick Man since they appear to be different from modern Indians and obviously were wiped out by them.
------------------
Bringer of fire, trickster, teacher.

This message is a reply to:
 Message 124 by Mammuthus, posted 10-11-2003 2:25 PM Mammuthus has replied

Replies to this message:
 Message 129 by Mammuthus, posted 10-12-2003 8:55 AM Speel-yi has replied

  
Speel-yi
Inactive Member


Message 127 of 159 (60596)
10-12-2003 3:58 AM
Reply to: Message 125 by NosyNed
10-11-2003 2:38 PM


quote:
I still don't quite get it. What about the divergent DNA? Isn't it different enough to both not come from contamination and to separate us from the neanderthals?
Or is that whole samples are rejected and there is the possibility of some heanderthals not being all tha divergent?
The contaminated DNA would be modern and since older DNA that looked like modern DNA it is assumed to be the contaminated sample. I think you sum it up in your second statement if I read it right.
Not really sure if will help, but try this link:
http://www.actionbioscience.org/evolution/johanson.html
It also might help if you think about what a species is in the first place. A dachshund and a great dane may be the same species, but the chances of offspring are slight unless they get a little help. However, the first thing two populations of a species will do when they come into contact is exchange genes if at all possible. I see no reason why anyone would expect older forms of Homo to be unable to interbreed with newer forms.
One other thing is that you would expect Africa to have larger populations of hominids than any of the other regions due to its favorable climate and thus contribute more to the genetics of modern humans in that way.
Try the link and see if that helps.
------------------
Bringer of fire, trickster, teacher.
[This message has been edited by Speel-yi, 10-12-2003]

This message is a reply to:
 Message 125 by NosyNed, posted 10-11-2003 2:38 PM NosyNed has not replied

Replies to this message:
 Message 131 by sfs, posted 10-13-2003 1:04 AM Speel-yi has replied

  
Mammuthus
Member (Idle past 6475 days)
Posts: 3085
From: Munich, Germany
Joined: 08-09-2002


Message 128 of 159 (60620)
10-12-2003 8:50 AM
Reply to: Message 125 by NosyNed
10-11-2003 2:38 PM


Hi Nosy,
As Speel-yi pointed out, your last sentence is what I mean. Samples are rejected if the sequence obtained from them look modern but are accepted if they look divergent. Culling the samples that give results you don't like is not good science...
I am not questioning that validity of the published neandertal sequences. There were clearly neandertals that were divergent relative to modern mtDNA sequences. However, we don't really know what ancient human mtDNA diversity looked like and there is evidence that H. sapiens has been subjected to genetic bottlenecks so that our current mtDNA diversity may not be representative of the overall historical diversity. For example, the Mungo Lake sample from Australia which was modern human but a fairly old sample had a very divergent sequence....and guess who showed up to claim it must be a contaminant? Cooper...so if it is too modern like it is a contaminant, if it is to divergent it is a contaminant.
I have a real problem with a lot of the human molecular evolutionists because of crap like this...I think one should be extremely sceptical of broad claims about human ancestry based on a couple of sequences from fossils reported by scientific camps that hate each other.

This message is a reply to:
 Message 125 by NosyNed, posted 10-11-2003 2:38 PM NosyNed has not replied

  
Mammuthus
Member (Idle past 6475 days)
Posts: 3085
From: Munich, Germany
Joined: 08-09-2002


Message 129 of 159 (60622)
10-12-2003 8:55 AM
Reply to: Message 126 by Speel-yi
10-12-2003 3:36 AM


I agree completely though the idea that humans were present earlier than 12 kya is starting to gain support though tentative. There are also south American sites that are really old.
I see some of the same logic applied to extinction i.e. mammoths and other Pleistocene megafauna. It is assumed widely that a small number of humans went Rambo and killed every last mammoth, giant sloth, cave bear, sabre-tooth, etc. in about 1000 years, left the buffalo alone and then became relatively ecologically minded native Americans. All this with about a total of 12 confirmed mammoth kill sites in hand as evidence. But it sounds cool to think that it happened this way so it is probably the most accepted idea out there replacing climate change...and ignoring what I am interested in which is the potential for disease to mediate extinction.

This message is a reply to:
 Message 126 by Speel-yi, posted 10-12-2003 3:36 AM Speel-yi has replied

Replies to this message:
 Message 130 by Speel-yi, posted 10-12-2003 3:42 PM Mammuthus has not replied
 Message 138 by Rei, posted 10-14-2003 3:48 AM Mammuthus has replied

  
Speel-yi
Inactive Member


Message 130 of 159 (60634)
10-12-2003 3:42 PM
Reply to: Message 129 by Mammuthus
10-12-2003 8:55 AM


The problem with the Monte Verde site is that is was so poorly done, they did not use good methods at all. There was enough evidence there that it did look good to a fair number of experts, so it is generally accepted as having a legitimate date. Not much else will come from it I think because it is so poorly done. There are a few die hards that don't accept it.
The problem is that we won't see many older sites until funding allows for the possibility that humans lived in the Americas before 12 KYA. Any site having old C-14 dates is excluded. What kind of science is that? I have to think that careerism is coming in before good science.
Martin's pliestocene overkill is not generally accepted here, there's a couple of other hypotheses being kicked around, but my personal favorite involves a theory with human predation altering the environment enough to cause heavily k-selected species like mammoths to be outcompeted by smaller, faster reproducing species.
Interesting stuff about Paabo and Cooper, I'd love to see some challenges to their methods because a lot of people are taking conclusions at face value. I think it also ignores some morphological evidence.
Check the next link out, as it has some interesting points to ponder:
http://cogweb.ucla.edu/ep/Neanderthal.html
------------------
Bringer of fire, trickster, teacher.

This message is a reply to:
 Message 129 by Mammuthus, posted 10-12-2003 8:55 AM Mammuthus has not replied

  
sfs
Member (Idle past 2533 days)
Posts: 464
From: Cambridge, MA USA
Joined: 08-27-2003


Message 131 of 159 (60677)
10-13-2003 1:04 AM
Reply to: Message 127 by Speel-yi
10-12-2003 3:58 AM


quote:
One other thing is that you would expect Africa to have larger populations of hominids than any of the other regions due to its favorable climate and thus contribute more to the genetics of modern humans in that way.
Yes, that is the multiregional explanation, but I really don't see how it can be made to work quantitatively. Based on either the genetic diversity or on the amount of linkage disequilibrium, non-Africans look like a very small population -- their effective population size is no more than a few thousand. How could that small a population be spread across all of Eurasia and form viable subpopulations in multiple regions, with enough population density between them to support substantial gene flow? Especially since that kind of structured population preserves more diversity than a single population of the same size.
Add the fact that European and Asian populations show signs of having passed through a substantial bottleneck, and the fact that their common alleles are, the great majority of the time, a subset of African alleles, and the weight of the genetic evidence is heavily on the side of African replacement. Whether it was a complete replacement or not is not clear, but it seems to be have been pretty thorough-going.

This message is a reply to:
 Message 127 by Speel-yi, posted 10-12-2003 3:58 AM Speel-yi has replied

Replies to this message:
 Message 132 by Speel-yi, posted 10-13-2003 1:40 AM sfs has replied

  
Speel-yi
Inactive Member


Message 132 of 159 (60680)
10-13-2003 1:40 AM
Reply to: Message 131 by sfs
10-13-2003 1:04 AM


sfs stated:
quote:
Whether it was a complete replacement or not is not clear, but it seems to be have been pretty thorough-going.
There's the sum of it, the more people take an honest, objective look at all of the evidence, the more Out of Africa looks like MRH. It doesn't matter how big the populations were, since they remained viable for hundreds of thousands of years in their respective regions.
Migration did occur and the resultant hybrids were able to select the most suitable genes for each region. The end result is that each hybrid was better suited to each environment than either of the parent populations.
------------------
Bringer of fire, trickster, teacher.

This message is a reply to:
 Message 131 by sfs, posted 10-13-2003 1:04 AM sfs has replied

Replies to this message:
 Message 133 by sfs, posted 10-13-2003 9:41 PM Speel-yi has replied

  
sfs
Member (Idle past 2533 days)
Posts: 464
From: Cambridge, MA USA
Joined: 08-27-2003


Message 133 of 159 (60797)
10-13-2003 9:41 PM
Reply to: Message 132 by Speel-yi
10-13-2003 1:40 AM


quote:
There's the sum of it, the more people take an honest, objective look at all of the evidence, the more Out of Africa looks like MRH. It doesn't matter how big the populations were, since they remained viable for hundreds of thousands of years in their respective regions.
Of course it matters how big the ancestral populations of non-Africans were: if they were really small, then they weren't the archaic non-African populations that were in place, since they had to be larger.
To clarify my previous statement: at present, the evidence from human genetics, taken as a whole, indicates a complete replacement of non-African archaic populations by African ones. It is possible that some admixture did occur and the evidence has either been lost or lies in loci that haven't been examined yet, but at this point there is no such evidence.
That's genetics. What other evidence suggests I am no competent to comment on.

This message is a reply to:
 Message 132 by Speel-yi, posted 10-13-2003 1:40 AM Speel-yi has replied

Replies to this message:
 Message 135 by Speel-yi, posted 10-13-2003 10:38 PM sfs has replied

  
sfs
Member (Idle past 2533 days)
Posts: 464
From: Cambridge, MA USA
Joined: 08-27-2003


Message 134 of 159 (60802)
10-13-2003 9:57 PM
Reply to: Message 121 by Mammuthus
10-11-2003 8:23 AM


quote:
And I personally don't care whether multi-regionalism or out of Africa is correct or whether or not neandertals and H. sapiens interbred.
If I had to choose one as being more interesting, it would be neandertal/H. sap interbreeding, but so far nature hasn't asked my opinion. I have very little stake in the answer, as it happens, since I was a physicist while most of the debate was going on and wasn't paying any attention. Also, my institution does primarily medical genetics and has no position to defend, which is nice. (Although it does mean that some population geneticists sneer at us when we do population genetics. For some reason population geneticists spend a lot of time sneering at each other.)

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 Message 121 by Mammuthus, posted 10-11-2003 8:23 AM Mammuthus has not replied

Replies to this message:
 Message 136 by Quetzal, posted 10-14-2003 2:35 AM sfs has replied

  
Speel-yi
Inactive Member


Message 135 of 159 (60813)
10-13-2003 10:38 PM
Reply to: Message 133 by sfs
10-13-2003 9:41 PM


quote:
Of course it matters how big the ancestral populations of non-Africans were: if they were really small, then they weren't the archaic non-African populations that were in place, since they had to be larger.
Why would they have to be larger? Larger than the Africans or larger than the regional populations? How can it be if they were really small, that they were then the archaic non-Africans?
What I'm saying is that the populations may have been small, but that they were able to migrate, exchange genetic information and continue to exist for a long time well before the African genetic migration.
quote:
To clarify my previous statement: at present, the evidence from human genetics, taken as a whole, indicates a complete replacement of non-African archaic populations by African ones. It is possible that some admixture did occur and the evidence has either been lost or lies in loci that haven't been examined yet, but at this point there is no such evidence.
Part of the problem is that mtDNA is only transmitted through the mothers line. I know it doesn't mean much, but if you look at mtDNA closely enough, you could see that a paternal grandmother would not be related to her grandson and that if a woman produced no sons, then her mtDNA line will disappear. If a woman produces more daughters, then her mtDNA is disprortionately represented in the next generation.
We also assume that the mitochondrial Eve was not the only woman of her generation, but that she had 10,000 women in her cohort. So we apply a rule that tells us about the other women of her day, but then somehow expect the rules to behave differently a hundred millenia later when people migrate out of Africa.
------------------
Bringer of fire, trickster, teacher.

This message is a reply to:
 Message 133 by sfs, posted 10-13-2003 9:41 PM sfs has replied

Replies to this message:
 Message 137 by PaulK, posted 10-14-2003 3:47 AM Speel-yi has not replied
 Message 141 by sfs, posted 10-14-2003 10:42 AM Speel-yi has replied

  
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