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22-08-2012, 08:46   #1
slowburner
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That Neanderthal question.

The fact that between 1 - 4% of the genes which make up the modern Eurasian genome are Neanderthal, has generally been taken as evidence that the two populations interbred.

Perhaps not, concludes this research.

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Research raises doubts about whether modern humans and Neanderthals interbred

Findings point to common ancestry to explain genetic similarities

New research raises questions about the theory that modern humans and Neanderthals at some point interbred, known as hybridisation. The findings of a study by researchers at the University of Cambridge suggests that common ancestry, not hybridisation, better explains the average 1-4 per cent DNA that those of European and Asian descent (Eurasians) share with Neanderthals. It was published today, 13 August, in the journal PNAS.
In the last two years, a number of studies have suggested that modern humans and Neanderthals had at some point interbred. Genetic evidence shows that on average Eurasians and Neanderthals share between 1-4 per cent of their DNA. In contrast, Africans have almost none of the Neanderthal genome. The previous studies concluded that these differences could be explained by hybridisation which occurred as modern humans exited Africa and bred with the Neanderthals who already inhabited Europe.
However, a new study funded by the BBSRC and the Leverhulme Trust has provided an alternative explanation for the genetic similarities. The scientists found that common ancestry, without any hybridisation, explains the genetic similarities between Neanderthals and modern humans. In other words, the DNA that Neanderthal and modern humans share can all be attributed to their common origin, without any recent influx of Neanderthal DNA into modern humans.
Dr Andrea Manica, from the University of Cambridge, who led the study said: "Our work shows clearly that the patterns currently seen in the Neanderthal genome are not exceptional, and are in line with our expectations of what we would see without hybridisation. So, if any hybridisation happened - it's difficult to conclusively prove it never happened - then it would have been minimal and much less than what people are claiming now."
Neanderthals and modern humans once shared a common ancestor who is thought to have spanned Africa and Europe about half a million years ago. Just as there are very different populations across Europe today, populations of that common ancestor would not have been completely mixed across continents, but rather closer populations would have been more genetically similar to each other than populations further apart. (There is extensive genetic and archaeological evidence that population in Africa were 'structured'; in other words, different populations in Africa only had limited exchange through migration, allowing them to remain distinct from each other both in terms of genetics and morphology.)
Then, about 350-300 thousand years ago, the European range and the African range became separated. The European range evolved into Neanderthal, the African range eventually turned into modern humans. However, because the populations within each continent were not freely mixing, the DNA of the modern human population in Africa that were ancestrally closer to Europe would have retained more of the ancestral DNA (specifically, genetic variants) that is also shared with Neanderthals.
On this basis, the scientists created a model to determine whether the differences in genetic similarities with Neanderthal among modern human populations, which had been attributed to hybridisation, could be down to the proximity of modern humans in northern Africa (who would have later gone on to populate Europe) to Neanderthals.
By examining the different genetic makeup among modern human populations, the scientists' model was able to infer how much genetic similarity there would have been between distinct populations within a continent. The researchers then simulated a large number of populations representing Africa and Eurasia over the last half a million years, and estimated how much similarity would be expected between a random Neanderthal individual and modern humans in Africa and Eurasia.
The scientists concluded that when modern humans expanded out of Africa 60-70K years ago, they would have brought out that additional genetic similarity with them, making Europeans and Asians more similar to Neanderthals than Africans are on average – undermining the theory that hybridization, and not common ancestry, explained these differences.
Dr Manica added: "Thus, based on common ancestry and geographic differences among populations within each continent, we would predict out of Africa populations to be more similar to Neanderthals than their African counterparts - exactly the patterns that were observed when the Neanderthal genome was sequenced; but this pattern was attributed to hybridisation. Hopefully, everyone will become more cautious before invoking hybridisation, and start taking into account that ancient populations differed from each other probably as much as modern populations do."
###
For additional information please contact:
Genevieve Maul, Office of Communications, University of Cambridge
Tel: direct, +44 (0) 1223 765542, +44 (0) 1223 332300
Mob: +44 (0) 7774 017464
Email: Genevieve.maul@admin.cam.ac.uk
http://www.eurekalert.org/pub_releas...-rrd081312.php
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23-08-2012, 09:45   #2
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I'm not so sure. The separation between what were going to become moderns and Neandertals kicked off around 600,000 years ago and we had diverged by 300,000 years ago. So how come African folks didn't hang onto these commonalities? In order for north Africans that led to us hanging onto them then they were getting jiggy with European/Levantine peoples throughout that time so that still shows hybridisation. I don't buy that one either. Evidence in the stones and bones shows us and them hanging out for 10,000 years in the Levant, in the same areas, cheek to jowl in neighbouring caves and that's when the genetic clocks seem to suggest we got all romantic. That makes more sense than this theory. To my mind anyway.
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24-08-2012, 12:17   #3
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So how come African folks didn't hang onto these commonalities?
I think the argument is that the more southern Modern human African populations were derived from a different gene pool (of the same species), than their North African counterparts.. The argument being that Neandertals at some earlier point evolved from this same North African gene pool, which is being used to explain the commonalities..
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24-08-2012, 17:47   #4
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Yea, but I'm not quite sure I buy that. It would also suggest quite a different and isolated group of south African humans that had pretty much no genetic contact with north eastern humans for 100,000's of 1000's of years an kinda evolved modernity all on their ownsome. That what became non African humans(outside of the northern lads) never went south within their own continent yet happily traipsed as far as Australia pretty quickly.

Aside... on that score I wonder do the various "negritos" scattered along the islands of south Asia like the Andamans have Neandertal DNA? They have very old African DNA and actually look exactly like shorter than average sub Saharan Africans. If they don't and I suspect they don't, then that's interesting in that it shows many separate modern human migrations from Africa, or my personal take that some ran along the coast avoiding previous people in the interior, while others went inland. Folks like the Andamans are isolated relicts of the former travelers. We can forget that when we left Africa it wasn't into virgin territory(except for Australia and some islands. Hell Flores "hobbits" got to an island in the middle of nowhere). There were people living in these lands for over a million years. We don't know how aggressive they or we were, how territorial etc. We likely applied caution in our earliest movements, which were probably small scale groups at first. Us bumping into a tribe of Denisovans may have gone either way.

Hey maybe north eastern humans didn't go into southern Africa. In historical times it seems they didn't range much beyond the shores of the nile. It does seem odd if it is the case as it would make Southern Africans even with their biggest genetic diversity isolates as a group for at least 200,000 years. Maybe they didn't have the "wanderlust gene" to nearly the same degree as their northeastern cousins, hence the huge diversity? Possibly. Funny enough they didn't attempt to colonise Zanzibar or Madagascar which they could see on a clear day so maybe? Ah no hang on, naw I'm talking arse here, no I still don't buy this paper at all.

Of course we still have proof of interbreeding with archaic humans. The Denisovans in Asia are a given. Then we have the curious findings that the Neandertal genes found in Asians are different to those found in Europeans. This latter thang kinda seals the deal for me that we did indeed interbreed. On top of that I'll make a prediction. They're currently sequencing Otzi the iceman lads DNA and I'll put money down he's got more Neandertal DNA than average. Basically cos he was closer in time to the jiggy jiggy. I'll place that betting chip on any other older neolithic DNA that comes up too.


EDIT Actually I've just thought of a Game Over for this paper. The ancient human bottleneck that occurred around 60-70,000 years ago(IIRC). Dirty great feckoff eruption screwed the environment and reduced us modern humans in Africa down to a few thousand(likely killed off a load of other archaic folks too). So all humans today are related to that smallish African group. In which case that paper has to be wrong, because we should all then have Neandertal DNA or we all shouldn't but we do, ditto for Denisovan DNA. So yea, game over man, game over...

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25-08-2012, 14:12   #5
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I was just getting into a good debate in my own head until I just read Wibbs's QED paragraph.......
Now I have to entertain myself in other ways for the afternoon.......
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25-08-2012, 15:26   #6
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EDIT Actually I've just thought of a Game Over for this paper. The ancient human bottleneck that occurred around 60-70,000 years ago(IIRC). Dirty great feckoff eruption screwed the environment and reduced us modern humans in Africa down to a few thousand(likely killed off a load of other archaic folks too). So all humans today are related to that smallish African group. In which case that paper has to be wrong, because we should all then have Neandertal DNA or we all shouldn't but we do, ditto for Denisovan DNA. So yea, game over man, game over...
Just to play devils advocate... Couldn't that small human population have been split into separate geographic populations scattered about the continent? With say 5 thousand North African survivors and 10 thousand South Africans? Thus retaining the integrity of these two separate gene-pools?
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25-08-2012, 21:29   #7
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OH sure, it could certainly have worked like that SD. It's even more logical when ya think about it. However other genetic studies looking at this bottleneck showed it seemed to be a homogenous group. In fact that's how they spotted the bottleneck in the first place. We went from diversity to very narrow and then went back to diversity again. The only real explanation was we were reduced to a small group in one area, relative on both small and same.

What interests me is what was going on with the other humans, the archaic ones about at the time. My suspicion is that our bottleneck as well as killing off moderns and archaics, also isolated us and archaics for a while, so diversity is lost until our populations start to grow and spread and indeed get jiggy with archaics. Not just in the near east and Asia either. In one of my drunken crystal ball moments a good while back I suggested that African folks fr from having no archaic mixes of their own, actually did get jiggy with other African archaics. Just that the preservaton of the evidence in that continent isn't conducive to extracting DNA like we have in Europe and Asia. Well some serious genetic brainiacs have recently noted some anomolies on African DNA that does seem to suggest just this. Makes perfect sense. "We" didn't just spring up in north east Africa and then as a "pure" modern human populate the world and completely replace all other folks. Well that;s what the "Out of Africa", near gospel for a while, theory states. Never bought it myself. Neither do I buy the pure multiregional theory either. Why da fug do scientists all too often dig trenches in a black and white fashion? Anyhooo...

My take is that we're mostly a north African Homo Erectus mark 2.0 that had a little something extra that marked us out, We left Africa and met other Homo Erectus mark 2.0 folks and got funkay with each other. In Africa we did the same spreading throughout that continent and getting funkay with others. In Europe/near east it was with Neandertals, in Asia it was with Denesovian folks and possibly more primitive Erectus mark 1.5. I'd say the more we dig and the more we can extract this evidence we'll see even more admixtures going back and forth and not just genetically. In my humble some cultural stuff too. It seems according to some Spanish researchers that Neandertals may have had pigment body art and adornments(pendants and the like) before our widespread use of them(some interesting shít coming out of Italy about Neandertals hunting and using particular bird feathers for some reason. It seems they dug black feathers). It was always assumed we were the cultural guys. Yes we had some examples of it, in southern Africa for example with scratced ochre, but it didnt seem to stick for long. We spread around into Eurasia and this stuff really kicks off and spreads around all of us. It's well possible that one of the reasons was meeting our cousins and that's what made us, Homo Erectus mark 2.5. The more we learn about them and us, the smaller the gaps between us get. It's fascinating stuff.
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25-08-2012, 22:43   #8
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The more we learn about them and us, the smaller the gaps between us get. It's fascinating stuff.
Indeed it is.. Genetic shift from one gene pool to another is a complicated thing to map, over complicated, in my mind, by our insistence on labeling the diverse populations of hominids of the time as separate species (in the traditional sense of the word). The very idea of species has become less and less tangible as our understanding of evolutionary mechanics has increased.. It's arbitrary terminology, that probably hinders an understanding of the potential for gene transfer between the more closely related populations out there... Even terms like "hybridisation" are relics of an outdated understanding of taxonomy in my mind...
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18-12-2012, 10:32   #9
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New research from Mezmaiskaya cave, in the northern Caucasus, and Ortvale Kide, in the southern Caucasus, indicates that Neanderthal populations may have been extinct before the arrival of modern human populations.

http://www.sciencedirect.com/science...47248412001479

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18-12-2012, 23:24   #10
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I dunno SB, I've a couple of problems with that.

1) that's just one site and can hardly be extrapolated to others. The archaeological record in many sites shows Neandertal tool technology datable to later than what they're suggesting. Hell the Gibraltar sites for one. The Chatelperronian sites another example. Now some reckon they aint our beetle browed cousins but I firmly believe they are. OK stone tools don't always give you who the tool user was, but they're generally quite indicative. EG if you find MOusterian tech in Europe, you figure Neandertals, because the moderns were using a slightly different tech before they come here so why would they revert? That's not to say there wasn't crossover of course(mousterian in North Africa for example). Some studies have found the Mousterian toolset can be just as efficient as the later "advanced" modern human stuff. Hardly surprising given the feckers developed it over 300,000 odd years, way longer than we've been around

2) modern humans have Neandertal genes and it turns out Otzi the iceman has more than modern populations(as I predicted a while back). Naturally as he was closer to the event. If we find any more archaic Sapiens DNA I'll put money down it'll have even more, particularly in the Middle East.

3) we also have Denisovan, more in fact if you're from east Asia, so we defo met them.

4) We have the sites in the middle east where it shows we were living cheek by jowl for a few thousand years. Interestingly the dates for that site line up with the dates of the genetic "clocks" for our shared DNA. It's well possible we only got jiggy in that one area or thereabouts. In any numbers anyway and it seems it takes some numbers to stay "in the blood". I look at England as an example. They had an historically recorded influx of Saxons who invaded both culturally and in bums on seats. Yet today the vast majority of that influx has vanished. Only a tiny amount of English people have Saxon DNA in their makeup and not a single line of Saxon female line has survived and we know they were about getting jiggy with the locals. Now maybe this is the rank ill learned amateur talking here, but for moderns to have up to 4% of Neandertal markers in our blood, suggests to me that for a time anyway we were getting jiggy on a pretty regular basis.

Other things may be in play in Europe and it's environs(and the Caucasus) things may well have been very different in the setup. Actually one thing I've noticed over time is how different we are in living areas in Europe. In the middle east we basically occupy the same areas and the same levels within them. In Europe, this changes. We generally take the "high ground" and they take the lower living areas in the valleys. Maybe a defensive thing on our part? I remember as a kid on holliers in Spain and France and noticing a difference compared to Ireland. Over there and ditto for Italy, the oldest villages and towns are on the top of hills for defensive reasons. They had to be what with all the back and forth invasions over many centuries. In Ireland(and the UK) we have some of that, but not nearly to the same degree. Many castles and keeps etc are in the bottom of valleys. More sited for the view than defence They seem to be as much for status and lording it over the locals, rather than any great worry about actual heavy duty defence. I suspect conditions in Europe back in the paleolithic made us more competitive, even aggressive towards each other because of that, hence no evidence yet of European Neandertal/Us jiggy jiggy

The other aspect is while we have quite an amount of Neandertal DNA(compared to other archaics) on file, we don't have that much and it's barely a snapshot of their genetic makeup. We may find later European Neandertals with us in them. These things ain't static. You're unlikely to find "pure" modern and "pure" Neandertal. Certainly there wasn't "One" Neandertal. They varied a fair bit in their bones anyway. You have the classical Neandertal and you also have the more gracile guys and gals. We do as a species love to draw lines and say "this is Black and this is White and this is the line Godammit". In fairness it's what sets us apart in many ways.

Hell, go back 100,000 odd years and we don't look that different. The early moderns from Ethiopia and such have huge feckin browridges and sloping foreheads and big teeth etc. Just to my eye they have a more rounded braincase and less swept back cheekbones and less of a muzzle, but it's not by a huge amount.

As I reckoned on another forum, here's a pic of "modern human" of that time;

and here's a pic of Neandertal;

NOt a lot of diffs going on. We've got a slightly flatter face, but actually we've also got slightly bigger and more globular brows. What f the African lad's skull was found in France and dated to 40,000 years? It would be a head scratcher. I'd reckon they'd say "Neandertal with some "modern" features". I note that Neandertal lad has a "chin" contrary to popular. His projecting mid face overpowers it, but it's there. I would suggest it's a slight case of rather than us gaining a chin, instead we lost the mid face projection.

OK so that was more than a "couple of problems" SB It's me for feck sake. I make the extra hard drives in Boards HQ look like their needed.

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19-12-2012, 08:04   #11
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I've only read the abstract (the full paper costs $19.95).
Presumably, the author draws some form of conclusion about changing climate in the Caucusus.
Is it safe to assume that the demise of the Neanderthal population was a climate related effect, as was the arrival of moderns?
In other words, did the climate deteriorate so much that Neanderthals moved away from the Caucusus, to be replaced by moderns as the climate improved?

It seems to me that there are three camps regarding the interbreeding question: those who like to think we did, those who shudder at the thought, and those who wait for the evidence.
The authors of this article, are I suspect, in the 'shudder at the thought' camp.
They prejudice the conclusion by stating that 'Neanderthal populations did not survive in the southern Caucusus after 37 ka cal BP, supporting a model of Neanderthal extinction'.

Perhaps there is evidence of 'extinction', but might this particular population not just have moved south?
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19-12-2012, 09:36   #12
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Perhaps there is evidence of 'extinction', but might this particular population not just have moved south?
Exactly. Nail on head SB. They survived for over 200,000 years through all sorts of climactic change including a couple of ice ages and hardly did that by staying put when conditions got iffy. Indeed more primitive humans of some sort have been roaming around Europe as far north as Scotland for nearly a million years. That's why the climate change model doesn't appeal to me as a reason they went extinct. A factor among many yea, but hardly the primary one.
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19-12-2012, 11:07   #13
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So what theory/theories do you have about their extinction?
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19-12-2012, 14:36   #14
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Good question and a complex one. I don't buy the lower technology or lack of adaptability or different diets. Not because of some research that shows their tools were just as good as ours and that they exploited more food sources than once though, but for the same basic reasons I don't buy the climate model. They survived and thrived in different environments over many hundreds of thousands of years doing quite well thanks very much.

My take? They seem to have never been very numerous in the landscape. For example unlike with when we show up, no large animals seem to go extinct with their presence(even with their bigger calorie requirement and unlike wolves etc they target the fittest members of the prey herds). So they were small isolated bands and seem to have been quite narrow genetically, so probably didn't meet up with each other that often. Apex predators like they were tend to be very small in number in an environment anyway and are vulnerable because of that. They appear to have the same birth rate cycle as us, but seem to have had fewer kids. It wouldn't take much of a difference between us on that score over thousands of years to show dfferent population dynamics.

I reckon we were "to blame" but not directly. Of all humans who've been around we grew/grow in numbers the most. Unusual for an apex predator. The others seem to reach an environmental set point/equilibrium and pretty much stay that way. We go beyond that. Why? Maybe we have slightly more kids? Maybe because we need less food so starvation kills fewer of us and it means we can live in smaller ranges? Maybe because we lived longer? This started to happen around 40,000 years ago. For some reason we had more peeps getting to be grandparents, which brings it's own advantages in passing on info.

So the two humans start roughly equal and small in number, but we have slightly more kids, more reach old age and pass on info, more kids means populations grow and bump into each other more and exchange info and tech and culture and genes and that becomes te perfect storm of advantage that quickly snowballs. They don't do that, they don't have the numbers, the Granny factors and wider exchanges of culture and tech and slowly but surely they become a smaller and smaller percentage in the landscape. On top of that as we grow we bump into them more and more. We may get along in some places and get jiggy, in others hostility might break out, in others our increasing numbers may have simply forced those who didn't engage with us to move on like they did in the face of increasing cold in the past, only this time the glaciers were us. This goes on over a very long period of time until there was nowhere really left for them to go to and the last of them simply petered out. Of course leaving some of our better contacts between us in us down to this day and I suspect in some of the last of them there was a fair bit of us in them too, until in most areas there was just "human".

NOt very dramatic, but I reckon more likely. I reckon similar also happened with all the other people who weren't us.

Last edited by Wibbs; 19-12-2012 at 14:40.
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18-09-2013, 16:45   #15
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Apologies for bringing up an old thread but there is some interesting new evidence concerning the Neanderthal diet which was widely believed not to include salmonids.
One theory even went so far as to propose that a diet rich in fish oil may have given H.sapiens an advantage in terms of brain development.

http://www.pasthorizonspr.com/index....s-ago-caucasus
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