A note to add to my previous post on the mtDNA C1 haplogroup in Europe, and new data regarding X2 haplogroup.
Before her 2014 paper (cited in my post on C1 hg), Der Sarkissian had studied the mtDNA sequenced from Northwestern Russian remains in her 2011 doctorate thesis . Her comments were prescient because in 2014 they were classified as a new hg: C1f; she wrote: "the Uznyi Oleni Ostrov C1 haplotype may in fact represent a distinct European-specific lineage" not linked to the C1 found among Western Siberians.
This Russian C1 was described as "a genetic outlier at the periphery of its proposed origin" (in South Western Central Asia) and its "absence... in other ancient and modern-day European populations suggests that the spread of haplogroup C did not reach further west into central Europe". 
She underlines its antiquity when she gives the reason that this haplotype survived for so long: the isolation of this group and maybe, the "closed mating system in isolation with other Mesolithic populations of Scandinavia" 
But orthodoxy imposes its imprint on the thesis, and the Amerindian C1b, C1c and C1d lineages are shown as "newer" (the image below shows this clearly) than the "older" Eurasian C1e and C1f lineages from Iceland and the Uznyi Oleni Ostrov site:
But the really interesting part is that Der Sarkissian points out that another mtDNA haplogroup X2 is very similar to the mtDNA C1 hg in that:
- It is found at relatively low frequencies in contemporary populations
- It has a very wide geographic range (from North America to Europe and also Siberia, the Middle East, North Africa and Central Asia)
These similarities suggest a similar evolutionary history for both X2 and C1.
Furthermore X2a (the Amerian clade) split early from the other ones; the split took place in the Middle East and from there the X2a carriers swiftly moved on into Siberia and accessed America in a second migratory wave, not long after the first wave. 
The X2 haplogroup
I recall reading about X2 when I was researching for my book (Monsters of Patagonia) back in 2009, and at that time thought that it was most likely due to admixture from contact with Europeans post-1492 discovery of America. This was founded on the idea that it was an Old World haplogroup and that it was only found among certain North American tribes that had been in direct contact with the French and English colonies in Canada and what would later become the US.
Furthermore I was reluctant to engage in further investigations because I found the Solutrean hypothesis as a source for the X2 mtDNA population was rather weak, and some theories regarding ancient Greek admixture into the Cherokees and other North American natives as too flimsy (I omit the Mormon theories and quack Atlanteans as totally non-scientific). There were no serious papers on these subjects and mostly posts in questionable - racist - supremacist forums made me drop further research, until now.
Encouraged by Der Srakissian's thesis I decided to look into the X2 hg once again, and came up with the following details, summarized below: 
- Haplogroup X has a wide geographic range covering Europe, North Africa, Asia and North America
- It descends from the ancient N haplogroup, dating back to at least 30 kya. It evolved from N in the Near East and surrounding areas of Western Eurasia
- It is currently found at very low frequencies in Europe (less than 5% of all MtDNA)
- Three populations carry it at high frequencies: Orkney Islanders (7%), Georgians 8%, Druze (11%) -The Druze have the greatest diversity of X lineages of any population X1a, X1c, X2b, X2e, X2f, X2h and X3 and their territory is very likely a refugia of the original X population .
- It is found among Neolithic Europeans at surprisingly high rates: Elau, Germany (4,6 kya), at 22.2%,  and 12.5% at Calden, Germany (3000 cal BC), . In these sites all carriers were X2 hg.
- It is split into two clades, X1 and X2: 
- X1 is found in North and East Africa, with entry routes along the coasts of the Red and Mediterranean seas
- X2 spans Eurasia and is also found in North American natives (X2a haplotype)
- X1 is higherst in Africa (36.8% of the X carriers there are X1)
- X2 prevails in the Middle East, Europe and South Caucasus (97.2% of X hg carriers are X2) and in Central Asia and Siberia (100%)
- X2a (the Amerindian clade) does not have any close relative in the Old World, including Siberia (Altaian X2e2a is another haplotype which is more recent). Was it lost due to genetic drift?
- X2a split very early from all other X2 haplotypes in the Middle East, right after X began to expand at the time of the Last Glacial Maximum (LGM)
- Coalescence time for X2a is 18,000 +⁄- 6,800 ya.
- X2a occurs only at a 3% frequency among North American Natives, so it is quite uncommon
- Its range in US and Canada is centered in the Great Lakes and the Western Plains, and has some outliers in Washington State and Arizona. Perego explains this range as caused by a central dispersion corridor from Beringia to the Great Lakes after the ice sheets receded 
- X2a prevails among the Algonquian natives such as the Ojibwe and Chipewa (25% frequency), and is strong among other natives to the West of them: Sioux (15%), Nuu-Chah-Nulth (13%), Navajo (7%), and Yakima(5%). The presence in the Navajo (Southern Na-Dene) is most probably due to recent admixture with other northern Native Americans
- It has not yet been detected in Central or South America
- The American haplotypes are: [*]
- X2a1a: Sioux and Tanoan speakers
- X2a1b: Ojibwe people
- X2a1c: Ojibwe people
♦X2a2: Nova Scotia and Newfoundland
[*] Perhaps there is even more diversity among Amerindians: Perego  classified an outlier X2g, that lacked the markers of X2a1 and was different from the other Old World X2 branches, suggesting another extremely rare founder line in America.
An interesting point regarding X's antiquity is "that the basic phylogenetic structures of the [X and U] mtDNA haplogroups in West Eurasia and North Africa are as ancient as the beginning of the spread of anatomically modern humans in this region." , which in this paper is dated as 23 - 36 kya, close to the LGM. X is believed to have undergone "a long incubation period coinciding with and following the most recent out of Africa expansion"  placing it even further back in time.
Time for my wild hypothesis...
It is old, Neanderthal old. It appeared in the heart of their Eurasian realm. Its current low frequency is due to sucessive overlays of modern human mtDNAs. It was more frequent in the past as shown by the German Neolithic remains. Some refugial areas on the fringes of Europe (Orkney Islands, the Caucasus and the Druze highlands) retained a higher frequency.
The eastern Neanderthals moved on, across Asia following the animals they hunted perhaps long before the H. sapiens OOA move. These Neanderthal peopled the New World. None remained in Siberia that is why it is not found there now. They entered America along the only available corridor open to them reaching the Great Lakes area.
I checked when this corridor was open earlier than 20 kya to provide an entry date into America and came up with the Sangamonian period 125 to 75 kya , so it is not so far fetched.
The Neanderthals settled there (perhaps their migration followed specific prey whose range ended there). They never moved on, further South. These were cold-climate people. Later waves of migrants occupied the rest of the New World, sealing these X2a carriers off in their current range.
But... X2 is a Homo sapiens mtDNA haplogroup, not a Neanderthal one. So the theory outlined above is wrong.
Yes, if we accept current timelines for mtDNA evolution. But if we consider that the times are underestimated, that the coalescense time for X2 is not 40 kya but 150 kya and that the African Eve is not so recent, and maybe even found in Eurasia... that perhaps the coalescense leadst to a non sapiens hominin, then it could be possible to accept the scenario outlined above.
I already mentioned something similar regarding the Y chromosome evolution, and am still trying to figure out how to write a post on this subject. The main objection I find is that the real Neanderhtal mtDNA that has been sequenced until now is very different to ours and lies on a distinct phylogenetic branch. Definitively more analysis is needed before I can post on this subject!
 Der Sarkissian, Clio, (2011). Mitochondrial DNA in Ancient Human Populations of Europe Doctorate Thesis Univ. of Adelaide, South Australia.
 Maere Reidla et al., (2003). Origin and Diffusion of mtDNA Haplogroup X Am J Hum Genet. Nov 2003; 73(5): 1178–1190. Oct 20, 2003. doi: 10.1086/379380
 Europedia, Haplogorup X (mtDNA) www.europedia.com
 Shlush LI, Behar DM, Yudkovsky G, Templeton A, Hadid Y, et al., (2008). The Druze: A Population Genetic Refugium of the Near East. PLoS ONE 3(5): e2105. doi:10.1371/journal.pone.0002105
 Haak et al., (2008). Ancient DNA, Strontium isotopes, and osteological analyses shed light on social and kinship organization of the Later Stone Age. PNAS November 25, 2008 vol. 105 no. 47 18226-18231 10.1073/pnas.0807592105
 Lee, E.J., et al., (2012). Collective burials among agro-pastoral societies in later Neolithic Germany: perspectives from ancient DNA. Journal of Archaeological Science.
 Ugo A. Perego et al., (2009). Distinctive Paleo-Indian Migration Routes from Beringia Marked by Two Rare mtDNA Haplogroups. Current Biology Volume 19, Issue 1, 13 January 2009, Pages 1–8. doi: 10.1016/j.cub.2008.11.058
 Peter C. Lent, Muskoxen and Their Hunters: A History. pp 18
Patagonian Monsters - Cryptozoology, Myths & legends in Patagonia Copyright 2009-2014 by Austin Whittall ©