Kazimiera
05-22-2013, 12:25 AM
I, W and X are all of very ancient European origin. They are estimated to have arisen approximately 30,000 years ago, a few thousand years before the extinction of Neanderthal. Although present in all Europe and a big part of Asia, from the Middle East to Siberia, and even in North America in the case of X, these three haplogroups never exceed more than a few percents of the population in every region (most often under 1%). They are most common in cold, mountainous or desertic climates. The highest densities of X and W are observed in the Caucasus, in North-East Europe, Siberia and Central Asia, while haplogroup I reaches unusually high levels (4 or 5%) in countries like Iceland, Scotland, Norway or Latvia.
One hypothesis is that these mtDNA haplogroups might be the only surviving haplogroups descended from a specific subspecies of Neanderthal. Neanderthals lived in Europe, and as far as North-West Asia and the Middle East, for over 200,000 years. They progressively disappeared over a period of 25,000 years after the arrival of Homo Sapiens from Africa. The most recent skeletons of Neanderthals found in Iberia (dating from 25,000 years ago) show obvious signs of Homo Sapiens admixture. Just like some White Americans nowadays carry Native American or African mtDNA without looking different from a "pure" European, it is thought that Neanderthals left some genes in modern humans, and maybe some mitochondrial lineages.
The Neanderthalian hypothesis is consistent with the estimated age and place of origin of these haplogroups - in Europe or Russia, just before the presumed extinction of Neanderthal. It correlates with the fact that haplogroups I, W and X now make up only a tiny minority of European haplogroups, while the descendants of haplogroup R (H, V, J, T, U and K), representing the better adapted Homo Sapiens, account for over 95% of the modern European population. Homo Sapiens would have progressively outnumbered, then assimilated the last Neanderthals. The same phenomenon is thought to have happened in Asia between the new wave of Homo Sapiens from Africa and the various indigenous species of Homo Erectus (e.g. Peking Man, Java Man, Man of Flores) .
The fact that only the mtDNA line (i.e. the maternal line) of Neanderthal has survived is also concordant. In primitive societies women were very likely to be raped, abducted by another tribe, or spared during tribal warfare and integrated to the winning tribe. A few isolated cases are enough to pass Neanderthalian mtDNA to the Homo Sapiens population.
Due to Neanderthal's long evolution and their adaptation to extreme climates, including several glaciations, the phylogenic tree of Neanderthal mtDNA could be as diversified, if not more, than that of modern humans. At present, only a handful of Neanderthal mtDNA has been tested, which may not be more characteristic of the whole Neanderthal species than a Papuan haplogroup would be of the whole Homo Sapiens species.
The main function of mitochondrial DNA in the body is to produce energy. Some mtDNA haplogroups have a strong correlation with a type of climate, suggesting that mtDNA may provide a better resistance to extreme temperatures. If so, it would have been beneficial to Homo Sapiens to inherit Neanderthalian mtDNA, better adapted to the cold climatic conditions, especially since Homo Sapiens lived side-by-side with Neanderthal during the last glacial period (70,000 to 10,000 years ago). Such haplogroups would have progressively faded out of the population once the weather got warmer, except in northern Europe, Siberia or Central Asia, where it was still somewhat useful for survival.
Homo Sapiens' Mitochondrial Eve, the most distant common ancestor to all Homo Sapiens female lineages, is estimated to have lived some 140,000 years ago. Imagine that at the time Homo Sapiens reached Europe, the Neanderthalian Mitochondrial Eve could already been 300,000 years old. The consequence of this would be that Neanderthals had twice or three times more genetic diversity than modern humans, and over ten times more than Homo Sapiens 50,000 years ago. When Homo Sapiens arrived in Europe, they only belonged to a few haplogroups (probably only HV, H, JT, U and U5). Hundreds of subclades have developed since then (e.g. K1a1b1a or J1b1). Any modern day version of Neanderthal mtDNA, had it survived to this day, is bound to be very different from that of a random Neanderthal subspecies who lived 100,000 years ago.
Nevertheless, many mutations found in haplogroup X show striking similarities with the random Neanderthal mtDNA analysed. Many are also shared by I and W.
http://www.eupedia.com/europe/Neanderthal_DNA.shtml
One hypothesis is that these mtDNA haplogroups might be the only surviving haplogroups descended from a specific subspecies of Neanderthal. Neanderthals lived in Europe, and as far as North-West Asia and the Middle East, for over 200,000 years. They progressively disappeared over a period of 25,000 years after the arrival of Homo Sapiens from Africa. The most recent skeletons of Neanderthals found in Iberia (dating from 25,000 years ago) show obvious signs of Homo Sapiens admixture. Just like some White Americans nowadays carry Native American or African mtDNA without looking different from a "pure" European, it is thought that Neanderthals left some genes in modern humans, and maybe some mitochondrial lineages.
The Neanderthalian hypothesis is consistent with the estimated age and place of origin of these haplogroups - in Europe or Russia, just before the presumed extinction of Neanderthal. It correlates with the fact that haplogroups I, W and X now make up only a tiny minority of European haplogroups, while the descendants of haplogroup R (H, V, J, T, U and K), representing the better adapted Homo Sapiens, account for over 95% of the modern European population. Homo Sapiens would have progressively outnumbered, then assimilated the last Neanderthals. The same phenomenon is thought to have happened in Asia between the new wave of Homo Sapiens from Africa and the various indigenous species of Homo Erectus (e.g. Peking Man, Java Man, Man of Flores) .
The fact that only the mtDNA line (i.e. the maternal line) of Neanderthal has survived is also concordant. In primitive societies women were very likely to be raped, abducted by another tribe, or spared during tribal warfare and integrated to the winning tribe. A few isolated cases are enough to pass Neanderthalian mtDNA to the Homo Sapiens population.
Due to Neanderthal's long evolution and their adaptation to extreme climates, including several glaciations, the phylogenic tree of Neanderthal mtDNA could be as diversified, if not more, than that of modern humans. At present, only a handful of Neanderthal mtDNA has been tested, which may not be more characteristic of the whole Neanderthal species than a Papuan haplogroup would be of the whole Homo Sapiens species.
The main function of mitochondrial DNA in the body is to produce energy. Some mtDNA haplogroups have a strong correlation with a type of climate, suggesting that mtDNA may provide a better resistance to extreme temperatures. If so, it would have been beneficial to Homo Sapiens to inherit Neanderthalian mtDNA, better adapted to the cold climatic conditions, especially since Homo Sapiens lived side-by-side with Neanderthal during the last glacial period (70,000 to 10,000 years ago). Such haplogroups would have progressively faded out of the population once the weather got warmer, except in northern Europe, Siberia or Central Asia, where it was still somewhat useful for survival.
Homo Sapiens' Mitochondrial Eve, the most distant common ancestor to all Homo Sapiens female lineages, is estimated to have lived some 140,000 years ago. Imagine that at the time Homo Sapiens reached Europe, the Neanderthalian Mitochondrial Eve could already been 300,000 years old. The consequence of this would be that Neanderthals had twice or three times more genetic diversity than modern humans, and over ten times more than Homo Sapiens 50,000 years ago. When Homo Sapiens arrived in Europe, they only belonged to a few haplogroups (probably only HV, H, JT, U and U5). Hundreds of subclades have developed since then (e.g. K1a1b1a or J1b1). Any modern day version of Neanderthal mtDNA, had it survived to this day, is bound to be very different from that of a random Neanderthal subspecies who lived 100,000 years ago.
Nevertheless, many mutations found in haplogroup X show striking similarities with the random Neanderthal mtDNA analysed. Many are also shared by I and W.
http://www.eupedia.com/europe/Neanderthal_DNA.shtml