Neanderthals
Geomagnetic Excursions
Geomagnetic excursions represent short episodes that last a few thousand years at most during which the field considerably exceeds its normal range of variability during a polarity state. The Laschamp event discovered in lava flows of Massif central (France) is the youngest and the most studied field excursion. Its geomagnetic origin has been controversial due to the existence of self-reversal processes. We have confirmed that reverse polarity flows are affected by self-reversals, but we found that this is also the case for normal flows. A direct consequence is that self-reversals cannot be taken as responsible for the reverse directions. We sampled a large collection of flows. New K-Ar dates by Gilles Gu�rin provided a coherent chronology of the successive polarities. The 37 ka old reverse directions of the Olby flow are consistent with the 41.9 kyr old normal polarity flows preceding the event. A younger flow with intermediate directions dated at 33.3 ka may be related to the Mono Lake event.
Surprisingly, no attention has been given to the fact that the Laschamp and Mono Lake events occurred during the period of Neandertal extinction (this is even clearer after recalibration of the 14C ages) which lasted for several thousand years. During this time interval the geomagnetic field strength was considerably reduced and shielding efficiency of the magnetosphere lowered, leaving energetic particles reach latitudes as low as 30�. The enhanced flux of high-energy protons (linked to solar activity) into the atmosphere yielded significant ozone depletion down to latitudes of 40-45�. A direct consequence was an increase of UV-B radiations at the surface by at least 15-20% in Europe with significant impacts for human populations. With Hne Valladas we suggest that these conditions, maybe added to other factors, have contributed to the demise of Neanderthal population.
Link between the Laschamp event and Neandertal demise (Quatern. Sci. Rev. 29, 2010).
We have compiled the most detailed records of excursions that occurred during the Brunhes and Matuyama chrons. The virtual geomagnetic poles (VGPs) of at least one record of each event are able to reach the opposite polarity. It is impossible to reach the ratio of reversed to intermediate VGPs present in the paleomagnetic records if the excursions were not associated with a short period of reversed dipole field. Therefore, excursions should be regarded as two successive reversals bracketing an aborted polarity interval. We propose that the same underlying mechanisms prevail in both situations (excursions or reversals) and that below a certain strength, the field reaches an unstable position which preludes either the achievement of a reversal or its return to former polarity. http://www.ipgp.jussieu.fr/~valet/
Besides giving evidence for a geomagnetic field reversal 41,000 years ago, the geoscientists from Potsdam discovered numerous abrupt climate changes during the last ice age in the analysed cores from the Black Sea, as it was already known from the Greenland ice cores. This ultimately allowed a high precision synchronisation of the two data records from the Black Sea and Greenland. The largest volcanic eruption on the Northern hemisphere in the past 100 000 years, namely the eruption of the super volcano 39400 years ago in the area of today's Phlegraean Fields near Naples, Italy, is also documented within the studied sediments from the Black Sea. The ashes of this eruption, during which about 350 cubic kilometers of rock and lava were ejected, were distributed over the entire eastern Mediterranean and up to central Russia. These three extreme scenarios, a short and fast reversal of the Earth's magnetic field, short-term climate variability of the last ice age and the volcanic eruption in Italy, have been investigated for the first time in a single geological archive and placed in precise chronological order.
Read more at: http://phys.org/news/2012-10-extremely-reversal-geomagnetic-field-climate.html#jCp
Geomagnetic excursions represent short episodes that last a few thousand years at most during which the field considerably exceeds its normal range of variability during a polarity state. The Laschamp event discovered in lava flows of Massif central (France) is the youngest and the most studied field excursion. Its geomagnetic origin has been controversial due to the existence of self-reversal processes. We have confirmed that reverse polarity flows are affected by self-reversals, but we found that this is also the case for normal flows. A direct consequence is that self-reversals cannot be taken as responsible for the reverse directions. We sampled a large collection of flows. New K-Ar dates by Gilles Gu�rin provided a coherent chronology of the successive polarities. The 37 ka old reverse directions of the Olby flow are consistent with the 41.9 kyr old normal polarity flows preceding the event. A younger flow with intermediate directions dated at 33.3 ka may be related to the Mono Lake event.
Surprisingly, no attention has been given to the fact that the Laschamp and Mono Lake events occurred during the period of Neandertal extinction (this is even clearer after recalibration of the 14C ages) which lasted for several thousand years. During this time interval the geomagnetic field strength was considerably reduced and shielding efficiency of the magnetosphere lowered, leaving energetic particles reach latitudes as low as 30�. The enhanced flux of high-energy protons (linked to solar activity) into the atmosphere yielded significant ozone depletion down to latitudes of 40-45�. A direct consequence was an increase of UV-B radiations at the surface by at least 15-20% in Europe with significant impacts for human populations. With Hne Valladas we suggest that these conditions, maybe added to other factors, have contributed to the demise of Neanderthal population.
Link between the Laschamp event and Neandertal demise (Quatern. Sci. Rev. 29, 2010).
We have compiled the most detailed records of excursions that occurred during the Brunhes and Matuyama chrons. The virtual geomagnetic poles (VGPs) of at least one record of each event are able to reach the opposite polarity. It is impossible to reach the ratio of reversed to intermediate VGPs present in the paleomagnetic records if the excursions were not associated with a short period of reversed dipole field. Therefore, excursions should be regarded as two successive reversals bracketing an aborted polarity interval. We propose that the same underlying mechanisms prevail in both situations (excursions or reversals) and that below a certain strength, the field reaches an unstable position which preludes either the achievement of a reversal or its return to former polarity. http://www.ipgp.jussieu.fr/~valet/
Besides giving evidence for a geomagnetic field reversal 41,000 years ago, the geoscientists from Potsdam discovered numerous abrupt climate changes during the last ice age in the analysed cores from the Black Sea, as it was already known from the Greenland ice cores. This ultimately allowed a high precision synchronisation of the two data records from the Black Sea and Greenland. The largest volcanic eruption on the Northern hemisphere in the past 100 000 years, namely the eruption of the super volcano 39400 years ago in the area of today's Phlegraean Fields near Naples, Italy, is also documented within the studied sediments from the Black Sea. The ashes of this eruption, during which about 350 cubic kilometers of rock and lava were ejected, were distributed over the entire eastern Mediterranean and up to central Russia. These three extreme scenarios, a short and fast reversal of the Earth's magnetic field, short-term climate variability of the last ice age and the volcanic eruption in Italy, have been investigated for the first time in a single geological archive and placed in precise chronological order.
Read more at: http://phys.org/news/2012-10-extremely-reversal-geomagnetic-field-climate.html#jCp
[Recalled Dream] The ground floor stood for the first level of the conscious.
The deeper I went, the more alien and darker the scene became. In the cave (under the house), I discovered the remains of a primitive culture, that is, the world of primitive man within myself - a world that can scarcely be reached or illuminated by consciousness.
The primitive psyche of man borders on the life of the animal soul, just as the caves of prehistoric times were usually inhabited by animals before men laid claim to them. ~Carl Jung; Memories Dreams and Reflections; Page 160.
The deeper I went, the more alien and darker the scene became. In the cave (under the house), I discovered the remains of a primitive culture, that is, the world of primitive man within myself - a world that can scarcely be reached or illuminated by consciousness.
The primitive psyche of man borders on the life of the animal soul, just as the caves of prehistoric times were usually inhabited by animals before men laid claim to them. ~Carl Jung; Memories Dreams and Reflections; Page 160.
http://www.sci-news.com/genetics/science-neanderthals-interbred-eurasians-01837.html
A new genetic study, published in the journal Genetics, supports the hypothesis that Neanderthals interbred with anatomically modern Homo sapiens in Eurasia.
Study co-author Dr Konrad Lohse from the University of Edinburgh explained: “our approach can distinguish between two subtly different scenarios that could explain the genetic similarities shared by Neanderthals and modern humans from Europe and Asia.”
The first scenario is that Neanderthals occasionally interbred with modern humans after they migrated out of Africa.
The alternative scenario is that the humans who left Africa evolved from the same ancestral subpopulation that had previously given rise to the Neanderthals.
Many anthropologists say the interbreeding scenario is more likely, because it fits the genetic patterns seen in studies that compared genomes from many modern humans.
By using only the information from one genome each of several types: Neanderthal, European/Asian, African and chimpanzee, Dr Lohse with colleagues completely ruled out the alternative scenario, revealing strong support for Neanderthal admixture in Eurasia at a higher rate (3.4-7.3 per cent) than suggested previously.
“Because the method makes maximum use of the information contained in individual genomes, it is particularly exciting for revealing the history of species that are rare or extinct.”
The method can more confidently detect the genetic signatures of interbreeding than previous approaches. In fact, the researchers originally developed it while studying the history of insect populations in Europe and island species of pigs in South East Asia, some of which are extremely rare.
Dr Lohse also said the new method estimates a slightly higher genetic contribution of Neanderthals to modern humans than previous studies.
“Estimating this contribution is complex and is likely to vary slightly between different approaches.”
“This work is important because it closes a hole in the argument about whether Neanderthals interbred with humans,” said Editor-in-Chief of the journal Genetics Dr Mark Johnston, who was not involved in the study.
“And the method can be applied to understanding the evolutionary history of other organisms, including endangered species.”
______
Konrad Lohse & Laurent A. F. Frantz. Neandertal Admixture in Eurasia Confirmed by Maximum Likelihood Analysis of Three Genomes. Genetics, published online February 13, 2014; doi: 10.1534/genetics.114.162396
A new genetic study, published in the journal Genetics, supports the hypothesis that Neanderthals interbred with anatomically modern Homo sapiens in Eurasia.
Study co-author Dr Konrad Lohse from the University of Edinburgh explained: “our approach can distinguish between two subtly different scenarios that could explain the genetic similarities shared by Neanderthals and modern humans from Europe and Asia.”
The first scenario is that Neanderthals occasionally interbred with modern humans after they migrated out of Africa.
The alternative scenario is that the humans who left Africa evolved from the same ancestral subpopulation that had previously given rise to the Neanderthals.
Many anthropologists say the interbreeding scenario is more likely, because it fits the genetic patterns seen in studies that compared genomes from many modern humans.
By using only the information from one genome each of several types: Neanderthal, European/Asian, African and chimpanzee, Dr Lohse with colleagues completely ruled out the alternative scenario, revealing strong support for Neanderthal admixture in Eurasia at a higher rate (3.4-7.3 per cent) than suggested previously.
“Because the method makes maximum use of the information contained in individual genomes, it is particularly exciting for revealing the history of species that are rare or extinct.”
The method can more confidently detect the genetic signatures of interbreeding than previous approaches. In fact, the researchers originally developed it while studying the history of insect populations in Europe and island species of pigs in South East Asia, some of which are extremely rare.
Dr Lohse also said the new method estimates a slightly higher genetic contribution of Neanderthals to modern humans than previous studies.
“Estimating this contribution is complex and is likely to vary slightly between different approaches.”
“This work is important because it closes a hole in the argument about whether Neanderthals interbred with humans,” said Editor-in-Chief of the journal Genetics Dr Mark Johnston, who was not involved in the study.
“And the method can be applied to understanding the evolutionary history of other organisms, including endangered species.”
______
Konrad Lohse & Laurent A. F. Frantz. Neandertal Admixture in Eurasia Confirmed by Maximum Likelihood Analysis of Three Genomes. Genetics, published online February 13, 2014; doi: 10.1534/genetics.114.162396
New research raises questions about the theory that modern humans and Neanderthals at some point interbred, known as hybridization. The findings suggest that common ancestry, not hybridization, better explains the average 1-4 per cent DNA that those of European and Asian descent (Eurasians) share with Neanderthals.
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."
http://www.sciencedaily.com/releases/2012/08/120813155521.html
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."
http://www.sciencedaily.com/releases/2012/08/120813155521.html
- There is now conclusive evidence that Neanderthals bred with Homo sapiens – a fact disputed for many years. Some scientists claimed the two species had never even met.
- Ancient human species, including Neanderthals, Denisovans and Homo sapiens mated with each other, resulting in an incredibly complex family tree.
- The Denisovans share up to 8 percent of their genome with a “super achaic” and totally unknown species that dates back around 1 million years.
- The results conflict with the theory that modern humans arose completely from one “out of Africa” migration more than 60,000 years ago that spread worldwide without mating with other early humans.
- About 1.5 to 2.1 percent of all people with European ancestry can be traced to Neanderthals.
- Proportions of Neanderthal DNA are higher among Asians and Native Americans, who also have small percentages of Denisovan DNA.
- 6 percent of the genome of Australian Aborigines and indigenous Papua New Guineans belong to the Denisovan species.
- The Han Chinese, native to East Asia, and the Dai people of southern China are related to both Neanderthals and Denisovans.
- Some indigenous people from Brazil, such as the Karitiana, are not only related to both Neanderthals and Denisovans, but they show relatively high genetic contributions from the Denisovans.
- Only 96 genes responsible for making proteins in cells are different between modern humans and Neanderthals. Intriguingly, some of the gene differences involve ones involved in both immune responses and the development of brain cells in people.
- Somewhere within these 96 genes may lay the answer to why Neanderthals and Denisovans became extinct.
- And least consequential of all, the Neanderthal woman’s parents were related, possibly half-siblings, or an uncle and niece. As evolutionary biologist Mattias Jakobsson stated, the incest finding “is more of an anecdote”. The results from one individual cannot be applied to an entire species, in the same way that the recent discovery of an incest family in Australia does not apply to the whole of the human race.
- See more at: http://www.ancient-origins.net/news-evolution-human-origins/entire-neanderthal-genome-finally-mapped-amazing-results-001138#.UrYbF9iFw6o.facebook
http://blogs.discovermagazine.com/gnxp/2012/02/neandertal-population-structure/
There’s a new paper out, Partial genetic turnover in neandertals: continuity in the east and population replacement in the west. Basically, using 13 mtDNA samples the authors conclude that it looks as if there was a founder effect for Neanderthals in Western Europe ~50 K years ago, generating a very homogenized genetic background for this particular population before the arrival of modern humans. Perhaps it’s just me, but press releases with headlines such as “European Neanderthals Were On the Verge of Extinction Even Before the Arrival of Modern Humans” strike me as hyperbolic. I’m also confused by quotes like the one below:
“The fact that Neanderthals in Europe were nearly extinct, but then recovered, and that all this took place long before they came into contact with modern humans came as a complete surprise to us. This indicates that the Neanderthals may have been more sensitive to the dramatic climate changes that took place in the last Ice Age than was previously thought”, says Love Dalén, associate professor at the Swedish Museum of Natural History in Stockholm.
There are several points that come to mind, from the specific to the general. First, from what I gather Neandertals were actually less expansive in pushing the northern limits of the hominin range than the modern humans who succeeded them. From this many suppose that despite the biological cold-adapted nature of the Neandertal physique they lacked the cultural plasticity to push the range envelope (e.g., modern humans pushed into Siberia, allowing them to traverse Beringia). One might infer from this that Neandertals were more, not less, sensitive to climate changes than later human populations. Second, there is the fact that as the northern hominin lineage one would expect that Neandertals would be subject to more population size variations than their cousins to the south during the Pleistocene due to cyclical climate change. This is not just an issue just for Neandertals, but for slow breeding or moving organisms generally. The modern human bottleneck is in some ways more surprising, because modern humans derive from a warmer climate. Finally, there is the “big picture” issue that though we throw these northern adapted hominins into the pot as “Neandertals,” one shouldn’t be surprised if they exhibit structure and variation. Non-African humans have diversified over less than 100,000 years, at a minimum the lineages which we label Neandertals were resident from Western Europe to Central Asia for ~200,000 years. Wouldn’t one expect a lot of natural history over this time?
Presumably the authors focused on mtDNA because this is copious relative to autosomal DNA, making ancient DNA extraction easier. I’m a bit curious how it aligns with the inference from the Denisovan paper that Vindija and Mezmaiskaya Neandertals both went through a population bottleneck using autosomal markers. The dates from the paper’s supplements are not clear to me, though it seems possible that they may have sampled individuals where the Vindija population may have been post-resettlement. At some point presumably we may be able to get a better sense of the source population of the Neandertal admixture into our own genomes if the genomic history of this population is well characterized.
February 26th, 2012 Tags: Neanderthals
by Razib Khan in Human Evolution, Paleontology | 7 comments | RSS feed | Trackback >
7 Responses to “Neandertal population structure”
Denisovans are in with the Asiatic Neanderthals, about as far removed from them as the Asiatics are from the European Neanderthals. They are NOT sufficiently different to warrant a new species
There’s a new paper out, Partial genetic turnover in neandertals: continuity in the east and population replacement in the west. Basically, using 13 mtDNA samples the authors conclude that it looks as if there was a founder effect for Neanderthals in Western Europe ~50 K years ago, generating a very homogenized genetic background for this particular population before the arrival of modern humans. Perhaps it’s just me, but press releases with headlines such as “European Neanderthals Were On the Verge of Extinction Even Before the Arrival of Modern Humans” strike me as hyperbolic. I’m also confused by quotes like the one below:
“The fact that Neanderthals in Europe were nearly extinct, but then recovered, and that all this took place long before they came into contact with modern humans came as a complete surprise to us. This indicates that the Neanderthals may have been more sensitive to the dramatic climate changes that took place in the last Ice Age than was previously thought”, says Love Dalén, associate professor at the Swedish Museum of Natural History in Stockholm.
There are several points that come to mind, from the specific to the general. First, from what I gather Neandertals were actually less expansive in pushing the northern limits of the hominin range than the modern humans who succeeded them. From this many suppose that despite the biological cold-adapted nature of the Neandertal physique they lacked the cultural plasticity to push the range envelope (e.g., modern humans pushed into Siberia, allowing them to traverse Beringia). One might infer from this that Neandertals were more, not less, sensitive to climate changes than later human populations. Second, there is the fact that as the northern hominin lineage one would expect that Neandertals would be subject to more population size variations than their cousins to the south during the Pleistocene due to cyclical climate change. This is not just an issue just for Neandertals, but for slow breeding or moving organisms generally. The modern human bottleneck is in some ways more surprising, because modern humans derive from a warmer climate. Finally, there is the “big picture” issue that though we throw these northern adapted hominins into the pot as “Neandertals,” one shouldn’t be surprised if they exhibit structure and variation. Non-African humans have diversified over less than 100,000 years, at a minimum the lineages which we label Neandertals were resident from Western Europe to Central Asia for ~200,000 years. Wouldn’t one expect a lot of natural history over this time?
Presumably the authors focused on mtDNA because this is copious relative to autosomal DNA, making ancient DNA extraction easier. I’m a bit curious how it aligns with the inference from the Denisovan paper that Vindija and Mezmaiskaya Neandertals both went through a population bottleneck using autosomal markers. The dates from the paper’s supplements are not clear to me, though it seems possible that they may have sampled individuals where the Vindija population may have been post-resettlement. At some point presumably we may be able to get a better sense of the source population of the Neandertal admixture into our own genomes if the genomic history of this population is well characterized.
February 26th, 2012 Tags: Neanderthals
by Razib Khan in Human Evolution, Paleontology | 7 comments | RSS feed | Trackback >
7 Responses to “Neandertal population structure”
- 1. Onur Says:
February 26th, 2012 at 7:32 pm None of the dates of the bottlenecked Western European Neanderthal specimens are prior to the modern human migration to Western Europe. The date of the Neanderthal bottleneck in Western Europe (<50,000 years before present) clearly coincides with the date of the appearance of modern humans in Western Europe (again <50,000 years before present) . It seems modern humans pushed Neanderthals to certain corners of Western Europe when they colonized Western Europe and this triggered a population bottleneck in Western European Neanderthals. Because that it would take longer for modern humans to colonize Eastern Europe with its harsh climate, Eastern [Western?-DD] European Neanderthals would preserve their earlier genetic structure longer.[ Does this mean"The Advent of Modern Humans in EASTERN Europe?" Basic wisdom has it they appeared in the East and went West. In articles, the Western European examples-out of NW Africa no doubt-are younger than their Eastern European counterparts by several thousand years-DD] - 2. Maju Says:
February 26th, 2012 at 11:23 pm Nice map, it helps a lot to see the big picture.
The only thing that this says is that the late West Neanderthals of Feldhofer, Vindija and El Sidrón were, matrilineally, descendants from a single population, which was distinct from their geographic predecessors of Valdegoba and Scladina but closely related to the “old school” Neanderthals from Italy. It can therefore be imagined that West and Central Europe were re-colonized from Italy (or maybe the nearby West Balcans).
Instead Caucasian and Altaian Neanderthals retained their distinct lineages. We lack info from the late Southern Iberian Neandetrhals, which I would imagine more archaic than their continental neighbors (but just a guess).
Feldhofer is characterized by a Micoquian culture (big almond shaped axes, often, but not in this case, intersped with Mousterian). Vindija and El Sidrón are both Mousterian. I say because I was kind of expecting this bottleneck to be related to Chatelperronian or other early UP techno-cultural expansion but there’s lack of data on that, I realize now.
Whatever the case the appearance is of a population replacement by Neanderthals on other Neanderthals with an Italian or Balcanic source. As Onur says, it is at least curious that those dates are already within the probable time-frame of H. sapiens penetration in Europe: Istallosko, the earliest Aurignacian site, is 47.7 calBP, 44.3 BP uncal., with even older “aurignacoid” dates existing in Swabia and a number of other loosely “aurignacian” sites at the Pyrenees, South Germany, etc. before 45 Ka calBP.
There is a modern (H. sapiens) individual dated to c. 55 Ka BP (OSL, stratigraphy) in Palestine (Emirian culture, considered precursor of other “Aurignacoid” groups). So we must realize that Neanderthals were already interacting with “us” since very early, even in Europe itself. - 3. Eurologist Says:
February 27th, 2012 at 3:23 am Not sure what is going on with this blog’s software, but my posts are no showing up. Another try:
I have a hard time with the authors’ interpretation. It all hinges on a very small number of early western specimen, and their dating.
If one believes the timing, there was an expansion of the tight group (blue in the figure) ~60,000ya. The other branches may very well have expanded, too – we have simply insufficient data prior to ~42,000ya.
Now, all or nearly all of the finds of the tight group are dated to when AMHs were already present in the region. Since the expansion occurred well beforehand, I don’t see a bottleneck, but rather a very strong selection event. Could this group have had physiological features that spared them? Were they resistant to newly brought-in diseases?
I also miss a discussion of the archeological context. Surely, instead of relying on the very few specimen we have, one should compare to known sites and occupation timings. IIRC, there indeed were expansions at some sites ~60,000ya and shortly before AMHs arrived.
Interesting also that none of the tight group survived the Phlegraean Fields eruption… - 4. Jacob Roberson Says:
February 27th, 2012 at 11:28 am I go into pop-sci articles expecting speculative scifi. - 5. Randall Parker Says:
February 27th, 2012 at 8:32 pm ~50 years ago??? - 6. Razib Khan Says:
February 27th, 2012 at 11:29 pm Since the expansion occurred well beforehand, I don’t see a bottleneck, but rather a very strong selection event. Could this group have had physiological features that spared them? Were they resistant to newly brought-in diseases?
i don’t understand what you’re trying to say. you don’t consider a selection event a bottleneck? - 7. Eurologist Says:
February 28th, 2012 at 2:41 am “you don’t consider a selection event a bottleneck?”
Perhaps I am misunderstanding something here, but my reading of the authors indicates that they place a bottleneck just before the expansion @ ~60kya — ~15-20ky before what I see as a selection event. My argument is that while there may have very well been a contraction (expected ~70ka-60ka ago due to climate), there are noteworthy logical fallacies, here.
Firstly, there is a strong ascertainment bias: the vast majority of specimen from which mtDNA has been extracted is of course the most recent material (<42kya).
If, on the one hand, the analysis indicates a population expansion 60-50kya, but on the other hand we have almost no data from that time period nor from the time until 42kya, then we cannot say much about the makeup of the population during that time.
Lacking that, a reasonable *conjecture* would be that *all* then-existing branches expanded – because the one that we *have* data from shows this pattern. Then, the only conclusion one is left with is that – although somewhat plentiful – all but the "blue" branch vanished with the arrival of AMHs. That's selection – not a bottleneck, at *that* time. And note – I am usually extremely cautious about selection.
In other words, envision figure one with another pink and green and yellow tree (think "little boxes" song), similar to the "blue" lineage – except the other ones didn't make it past 42kya. It's like our Sun or planets or Saturn's ring syndrome: we are hardwired to initially think – based on a single data point – they are exceptions – until we realize they are not.
Denisovans are in with the Asiatic Neanderthals, about as far removed from them as the Asiatics are from the European Neanderthals. They are NOT sufficiently different to warrant a new species
http://www.sciencedaily.com/releases/2009/04/090415075150.htm
Three Neanderthal Sub-Groups Confirmed ScienceDaily (Apr. 15, 2009) — The Neanderthals inhabited a vast geographical area extending from Europe to western Asia and the Middle East 30,000 to 100,000 years ago. Now, a group of researchers are questioning whether or not the Neanderthals constituted a homogenous group or separate sub-groups (between which slight differences could be observed). Paleoanthropological studies based on morphological skeletal evidence have offered some support for the existence of three different sub-groups: one in Western Europe, one in southern Europe and another in the Levant. Researchers Virginie Fabre, Silvana Condemi and Anna Degioanni from the CNRS Laboratory of Anthropology (UMR 6578) at the University of Marseille, France, have given further consideration to the question of diversity of Neanderthals by studying the genetic structure of the mitochondrial DNA (mtDNA) and by analyzing the genetic variability, modeling different scenarios. The study was possible thanks to the publication, since 1997, of 15 mitochondrial DNA (mtDNA) sequences (the mtDNa is maternally transmitted) that originated from 12 Neanderthals. The new study confirms the presence of three separate sub-groups and suggests the existence of a fourth group in western Asia. According to the authors, the size of the Neanderthal population was not constant over time and a certain amount of migration occurred among the sub-groups. The variability among the Neanderthal population is interpreted to be an indirect consequence of the particular climatic conditions on their territorial extension during the entire middle Pleistocene time period. Degioanni and colleagues obtained this result by using a new methodology derived from different biocomputational models based on data from genetics, demography and paleoanthropology. The adequacy of each model was measured by comparing the simulated results obtained using BayesianSSC software with those predicted based on nucleotide sequences. The researchers hope that one day this methodology might be applied to questions concerning Neanderthal cultural diversity (for example the lithic industry) and to the availability of natural resources in the territory. This could provide new insights into the history and extinction of the Neanderthals. Journal Reference:
A discriminant functions analysis for fossil Homo skulls. They basically fall into four natural groups (from the top)as Homo erectus, H. sapiens heidelbergensis (archaic Homo sapiens), H sapiens neanderthalensis (Neanderthals) and modern Homo sapiens, more distinctive from all the rest. There are sound reasons for including ALL of them in one species as Homo sapiens
Neanderthal distributions: basically Neanderthals inhabited the warmer zones to the South, below the tree line during the Last Ice Age: they also inhabited the tundra areas here marked Western Palearctic and Central Palearctics they seem to have lived by following the herds of herd mammals, picking off scavengers and finding winter kills. Below, the tree line in the Mediterranean area.
Below, areas of late-persisting Neanderthals around the European Fringe, Western Neanderthals. Eastern Neanderthals also persisted to this larte date (approx 25000 BC or later) in the Caucasusl Siberia and in the Mountainous regions of Central Asia. These areas are of interest because they are also areas from which eminate more recent reports of Wildmen. The black sanctuary areas indicated below were not supposed to have persisted nearly so long.
The following charts are from Austin Whittal's Patagonian Monsters site anvokithat Neanderthals might very well have headed into the Americas at an early date, possibly in reaction to the movements of humans Out of Africa in the era of 65000 to 35000 BC. Thcates the expansion of Neanderthal territories Eastward and the solid yellow indicates the area they were "Classically" said to inhabit.
http://patagoniamonsters.blogspot.com/2011/09/neanderthals-migration-to-america-part.html
Another map from Patagonian Monsters indicates that the frequency of certain persisting genes out of the Neanderthal Genome are not only found in North and South America, the frequencies are actually higher there than in the Old World.orized a large proportion of Neanderthal admixture present during the peopling of the Americas. Below, Maurice Burton's Neanderthals
Three Neanderthal Sub-Groups Confirmed ScienceDaily (Apr. 15, 2009) — The Neanderthals inhabited a vast geographical area extending from Europe to western Asia and the Middle East 30,000 to 100,000 years ago. Now, a group of researchers are questioning whether or not the Neanderthals constituted a homogenous group or separate sub-groups (between which slight differences could be observed). Paleoanthropological studies based on morphological skeletal evidence have offered some support for the existence of three different sub-groups: one in Western Europe, one in southern Europe and another in the Levant. Researchers Virginie Fabre, Silvana Condemi and Anna Degioanni from the CNRS Laboratory of Anthropology (UMR 6578) at the University of Marseille, France, have given further consideration to the question of diversity of Neanderthals by studying the genetic structure of the mitochondrial DNA (mtDNA) and by analyzing the genetic variability, modeling different scenarios. The study was possible thanks to the publication, since 1997, of 15 mitochondrial DNA (mtDNA) sequences (the mtDNa is maternally transmitted) that originated from 12 Neanderthals. The new study confirms the presence of three separate sub-groups and suggests the existence of a fourth group in western Asia. According to the authors, the size of the Neanderthal population was not constant over time and a certain amount of migration occurred among the sub-groups. The variability among the Neanderthal population is interpreted to be an indirect consequence of the particular climatic conditions on their territorial extension during the entire middle Pleistocene time period. Degioanni and colleagues obtained this result by using a new methodology derived from different biocomputational models based on data from genetics, demography and paleoanthropology. The adequacy of each model was measured by comparing the simulated results obtained using BayesianSSC software with those predicted based on nucleotide sequences. The researchers hope that one day this methodology might be applied to questions concerning Neanderthal cultural diversity (for example the lithic industry) and to the availability of natural resources in the territory. This could provide new insights into the history and extinction of the Neanderthals. Journal Reference:
- Fabre et al. Genetic Evidence of Geographical Groups among Neanderthals. PLoS ONE, 2009; 4 (4): e5151 DOI: 10.1371/journal.pone.0005151
A discriminant functions analysis for fossil Homo skulls. They basically fall into four natural groups (from the top)as Homo erectus, H. sapiens heidelbergensis (archaic Homo sapiens), H sapiens neanderthalensis (Neanderthals) and modern Homo sapiens, more distinctive from all the rest. There are sound reasons for including ALL of them in one species as Homo sapiens
- In a conference about the neanderthal genome, Carles Lalueza told to us that neanderthals didn't seem to come only from one group of hominids, because looking at their genome(s) they found that they came at least from two different groups, one of them being more closely related to us (modern humans) and the other diverged from our line earlier.
It seems that neanderthals' ancestors mixed with other archaic groups when they left Africa, although we don't know when and where.
It is possible that they come mainly from a group who diverged from us about a million of years ago, but then, once in Europe/Asia, these archaic hominids mixed again with another group of hominids more akin to us?
This may explain why neanderthals are anatomically quite different from us, but genetic information tell us another different history.
'This is ongoing research anyhow and we'll know better for sure some years from now.'
I hope so, it'd be very interesting to sequence more genomes from neanderthals and modern humans, but unfortunately the Neanderthal genome project already finished.
http://www.elcomerciodigital.com/v/20100828/cultura/proyecto-genoma-neandertal-concluido-20100828.html
Carles Lalueza is seeking for more neanderthal DNA in El Sidrón, but there's no enough money to start another project :(
http://www.elcomerciodigital.com/v/20100828/cultura/sidron-buscara-financiacion-europea-20100828.html
Antigen analysis suggests that modern Homo sapiens mixed with Neanderthals three separate times in different places, and with groups of Neanderthals that were more primitive or advanced relative to each other. Below is the initial DNA analysis chart showing how different Neanderthals were to the rest of us. The two curves do have a small degree of overlap in the zone marked between 15 and 20 genetic differances.
Neanderthal distributions: basically Neanderthals inhabited the warmer zones to the South, below the tree line during the Last Ice Age: they also inhabited the tundra areas here marked Western Palearctic and Central Palearctics they seem to have lived by following the herds of herd mammals, picking off scavengers and finding winter kills. Below, the tree line in the Mediterranean area.
Below, areas of late-persisting Neanderthals around the European Fringe, Western Neanderthals. Eastern Neanderthals also persisted to this larte date (approx 25000 BC or later) in the Caucasusl Siberia and in the Mountainous regions of Central Asia. These areas are of interest because they are also areas from which eminate more recent reports of Wildmen. The black sanctuary areas indicated below were not supposed to have persisted nearly so long.
The following charts are from Austin Whittal's Patagonian Monsters site anvokithat Neanderthals might very well have headed into the Americas at an early date, possibly in reaction to the movements of humans Out of Africa in the era of 65000 to 35000 BC. Thcates the expansion of Neanderthal territories Eastward and the solid yellow indicates the area they were "Classically" said to inhabit.
http://patagoniamonsters.blogspot.com/2011/09/neanderthals-migration-to-america-part.html
Another map from Patagonian Monsters indicates that the frequency of certain persisting genes out of the Neanderthal Genome are not only found in North and South America, the frequencies are actually higher there than in the Old World.orized a large proportion of Neanderthal admixture present during the peopling of the Americas. Below, Maurice Burton's Neanderthals