Bernard Sechel 2014 is a dream come true for people who want to learn about mysterious and rare mtDNA haplogroup U6. They created a phylogenetic tree of U6 based on 230 complete U6 sequences(Download Additional file 2 to view the tree), with age estimates for nearly every little U6 clade identified, and labeled the maternal origin of all 230 samples in the tree, which is very helpful for discovering U6 migrations. They also used 761 HVR1 U6 samples along with the 230 complete sequences to show frequencies of U6 subclades in North Africa, Sub Sahara Africa, the near east, and Europe in Table 1. I created a Google spreadsheet(click here to view it) of a more readable version of Table 1.

Bernard Sechel 2014's tree reveals that U6, which is estimated to be 35,457 years old, is most diverse in the Maghreb and defintley originated there. The tree also reveals many migrations of U6 to Europe and Sub Sahara Africa, but little could be learned about the history of U6 in the near east because so few of the 230 complete U6 sequences are from the near east.

It is incredible how widespread mtDNA haplogroup U was as 30,000-40,000 years ago. Over 30,000 year old U5, U8, U2 samples have already been found in the Gravettian culture of Europe, and during that time U2 was in South Asia, U6 was in northwest Africa, U8, U7, U9, and U1 lineages were likely in west Asia. A now extinct U subclade has also been found in a 24,000 year old sample from Siberia. Since Mesolithic and Upper Palaeolithic Europeans were pretty much fixated for mtDNA U and they had a variety of lineages(U5, U2e, U4, U8, U*), maybe related populations who were also fixated for U are responsible for its spread to north Africa and other parts of Eurasia.

I made guesses of when the U6 subclades found in the European and Sub Saharan African samples arrived in Europe and Sub Sahara Africa based on Bernard Sechel 2014's U6 phylogenetic tree.

Migrations to Europe

Some people's interpritation of Bernard Sechel 2014 is that there were major Palaeolithic and Mesolithic migrations of U6 into Europe, and I don't understand why. There are very few possibly Palaeolithic or even Neolithic European U6 clades, and they amount for a very small amount of total European U6. I think that most U6 in Europe arrived 6,000-3,000 years ago, primarily with U6a7a, U6a1a1a, and U6a3 lineages. Most of European U6 first arrived in Iberia and spread from there, but there are some more recent(after 3,000YBP) lineages which probably arrived in others areas of Mediterranean Europe, like Italy and spread in historical times to many areas of Europe like Britain, Germany, Poland, and Ukraine. There are also many U6 lineages in Iberia which arrived from north Africa in historical times, many seem to have arrived as recently as 500-1,000 years ago.

Since multiple major U6 clades in Europe probably arrived around 6,000-3,000 years ago, it's possibly there was some type of heavy contact between north Africa and Iberia during that time. There are no pre-historic U6 samples from Iberia but there are pre-historic mtDNA L(M-, N-) samples from Iberia, and all are around 4,000 years old, which is exactly when many U6 clades were migrating to Europe. Also a PCA from Daskalaki, E. 2014 fitted 4,000 year old Late Neolithic Spanish farmer Portalon around the same area as modern western and southern Iberians who have the highest amount of north African ancestry in Iberia would fit. This could be because north African migrations carrying mtDNA U6 were arriving or just arrived in Iberia around 4,000 years ago.

Palaeolithic: U6a1a2(consistent with being Palaeolithic), U6b4(possible), U6a1c(possible), U6a1d(possible)

5,000-4,000YBP: U6a7a1(very certain), U6a7a2a(very certain), U6a1a1a(very certain)

4,000-3,000YBP: U6a3a1(very certain), U6a3a2(very certain), U6a3a*(very certain), U6d1(possible)

3,000YBP-1500YBP: U6a6a1a(pretty certain), U6a7a2a3(possible), U6d1a(very certain), U6d3a(pretty certain), U6a3b1(very certain), U6a1b1b(pretty certain)

Last 1,000 years or so: U6b1a(very certain), U6a6a1a(pretty certain), U6a1b1a(very certain), U6a3b1d(very certain), U6a3b1a(very certain), U6a3c1(very certain), U6a6a1a(pretty certain), U6b2a(very certain), U6d3a(pretty certain), U6c1a(pretty certain), U6c1c(very certain), U6b1a1(pretty certain), U6a2a3a(pretty certain)

Hard to say: U6a9(last 26,000 years), U6a3r(last 19,000 years), U6a3e(last 5,000 years), U6a2a1a1a(last 7,000 years), U6a2a2a(last 10,000 years), U6a2c2(last 6,000 years), U6a2a4(last 19,000 years), U6a4a(last 10,000 years), U6a5c(last 13,000 years), U6a5d(last 13,000 years), U6a5a1(last 6,000 years), U6b2(last 7,000 years), U6c2(last 6,000 years), U6a7b1a(last 9,000 years) and U6a7c1(last 5,000 years), U6a1b3(last 17,000 years), U6a1b2(last 4,000 years), U6a2a3a(last 3,000 years), U6b2b(last 7,000 years), U6d1b(after 4,000 years), U6d1c(after 6,000 years)

U6a1(18,592YBP) is pretty much exclusive to northwest Africa and Europe. In Europe it obviously mainly took an Iberian route, because that is where it is most popular and most diverse in Europe.

U6a1 has four subclades, two of whom U6a1c(I gave the name) and U6a1d(I gave the name) are represented by single Iberian samples and could have arrived some 18,000 years ago. U6a1's two other subclades U6a1a(13,093YBP) and U6a1b(17,114YBP), have alot of diversity in Europe(especially in Iberia) but probably originated in north Africa.

U6a1a1 takes up 14.47% of Iberian U6 and 11.7% of northwest African U6, but is overall more popular in northwest Africa, so I doubt northwest African U6a1a1 is descended from European back migrations. U6a1a1 has two subclades, U6a1a1a(6,155YBP) and U6a1a1b. U6a1a1b is represented by a single Tunisian sample, which is great evidence the entire U6a1a1 branch originated in north Africa. All of U6a1a1a's subclades are represented by Iberian or just European samples, except for one which has a single Algerian representative. U6a1a1a appears to have spread to Europe in one wave out of northwest Africa around 3,000 years ago.

All European U6a1a1a either traces back to Iberia or decends from other migrations out of north Africa(of any it would be the Italian clades). It has two clades represented by single Italian representatives I named U6a1a1a1 and U6a1a1a3, and a German clade represented by a single sample I named U6a1a1a6. U6a1a1a2 is estimated to only be 642 years old and all of its samples are from England and the eastern United States, and therefore probably spread to the Americas from England in Colonial times. Since it appears U6a1a1a arrived in Europe about 3,000 years ago and that it doesn't just have clades from Iberia but also from England, Germany, and Italy, in Europe it must have spread with a people around 3,000 years ago who had reasons to be in Britain, Germany, Iberia, and Italy. The only people I can think of who fit that criteria are ancient Romans.

U6a1a2(16,172YBP), is the best canidate for a north African Upper Palaeolithic migration to Europe because it has two clades, Iberian U6a1a2a(2,585YBP), and Dutch U6a1a2b which has a single representative, and no none European samples. I think U6a1a2 likely originated in north Africa(just samples have not been found yet), and migrated to Europe around 5,000-3,000YBP like most European U6 did.

U6a1b(17,114YBP) has 4 subclades, one of which is represented by a single sample from southern Italy and it may be descended of Upper Palaeolithic migrations from north Africa. U6a1b obviously originated in north Africa, because one of its subclades is represented by a single Moroccan sample, and every clade that has European(only Iberian) samples also have Algerian samples. There is no way Iberian back migrations can explain that. U6a1b1b(2,585YBP) and U6a1b2a are Iberian subclades of U6a1b, I think they both most likely arrived in the Iron age or historical times. There are three U6a1b1a*(1,029YBP) samples from Portugal along with an Algerian subclade, and so U6a1b1a* most likely arrived in Portugal from north Africa around 1,000 years ago or more recently, and possibly migrated along with U6a1b1b and U6a1b2a.

U6a2c is estimated to be 6,549 years old and has two clades with single representatives, one from Armenia and one from Sweden. This suggests unlike its sister clade U6a2b which originated in east Africa, that U6a2c originated in west Eurasia. There are many possibly time periods that it arrived in Europe in. U6a2a4 has a single representative from central Italy, and could have arrived in the Upper Palaeolithic, and had to of arrived in the last 19,000 years.

East African U6a2a1a1(7,982YBP), has two clades and each is represented by a single sample, one is from the Netherlands and one from Ethopia. There are many possibilities for when and how it got to the Netherlands from east Africa.

U6a2a3a is estimated to be 3,457 years old and has a sample from Spain along with two north African samples. It could have migrated from north Africa to Spain anytime after 3,457YBP. U6a2a2 is estimated to be 10,610 years old and has two clades with single representatives, one from Portugal(I'll call it U6a2a2a) and one from Egypt(I'll call it U6a2a2b). I think that it migrated to Portugal and Egypt at some point from the Maghreb, after 10,000 years ago.

U6a4 is estimated to be 10,610 years old and has two clades with single representatives one from central Italy and one from Iraq, which probably means it originated in west Eurasia but there are many possible time periods it expanded in.

There are two Italian and one American(European origin?) samples that are basal clades of U6a5, and all could be of Palaeolithic origin. There is also a European subclade of U6a5a1(6,103YBP), and there are many possible times it arrived.

U6a7a(7,622YBP) migrated to Europe from north Africa probably around 5,000-3,000 years ago, in multiple waves or a single wave. Most U6a7a1(4,687) clades are European. pre-U6a7a1a(3,239) only has samples from France and probably originated in France, U6a7a1c(3,457YBP) probably originated in Italy, and may have spread to Sardinia and Germany in Roman times. U6a7a1b(1,405YBP) may have back migrated to north Africa from Iberia, because all of its clades except for one are European, or it was brought to Iberia from the Moors and from Iberia spread to Ukraine, Poland, and southern Italy. There are 5 other U6a7a1 clades and all are represented by single representatives, 4 of which are from Europe, and one is from Tunisia. The one from Tunisia is evidence U6a7a1 did not originate in Europe, but even if that's true U6a7a1 has likely been in Europe for over 4,000 years.

Interestingly U6a7a1a is estimated to only be 467 years old and every U6a7a1a sample traces their maternal line to two French sisters from the 1600's, so the first member must of been their mother and proves the age estimate is accurate.

U6a7a2a(4,159YBP) has 3 clades, one of them U6a7a2a1(2,585) may have originated in Britain, because it only has samples from Scotland and the eastern United Sates, and it probably arrived in Europe and or Britian around 4,000-3,000 years ago and may have a connection with Romans. The other two U6a7a2a subclades are represented by single individuals, one from New York(European origin) and one from Morocco. The New York(European origin) subclade of U6a7a2a may have migrated with the British subclade U6a7a2a1 around 4,000 years ago, or arrived separate at some point around 4,000 years ago.

U6a7b1(9,246YBP) and U6a7c1(4,554YBP) obviously originated in northwest Africa but have some Europeans subclades, and must have migrated to Europe from north Africa sometime after their births.

U6a3a is estimated to be 9,617 years old and most likely originated in north Africa, it migrated to Europe 4,000-1,500 years ago. U6a3a1(1,287YBP) only has two samples and each is from Iberia, the same is true for U6a3a1c(1,287YBP) except its two samples are from Finland. U6a3a1b(3,597YBP) has a clade with two samples from Virginia(British origin?) and a clade with one sample from Mooroco. This suggests U6a3a1 arrived in Iberia around 3,000 years ago and somehow got to Britain and Finland probably in historical times. U6a3c1(1,287YBP) is a west African subclade, but has a European subclade(did not specify on what type of European), so it somehow got to Europe in the last 1,000 years or so. U6a3e(5,216YBP) has two clades with single representatives, one from Morocco and one from Spain, and there are many possibly time periods that it arrived in Spain in.

U6a3r(name given by me) is represented by a single Bulgarian sample, and there are alot of possibly time periods it arrived in from north Africa, including Palaeolithic, and it must have arrived in the last 19,000 years. U6a6a1a(3,895YBP) has two subclades with single representatives, one from Spain and one from Morocco and could have arrived in Spain anywhere from 4,000YBP-historical times.

U6b1a obviously spread from Canary to Iberia after 1,500 years ago and possibly in the last 1,000 years, it is so obvious there is no reason to give the evidence. U6b2a(857YBP) has a sample from Poland and arrived in historical times. U6b2b is represented by only one Spanish sample and could have arrived anytime after the birth of U6b2 7,219 years ago. U6b is estimated to be 12,530 years old and one of its subclades; U6b4, is represented by three samples from western Iberia, and there are many possibly times it arrived.

U6d1(5,659YBP) has a European clade named U6d1a(1,719YBP) with three samples one from England, one from Ireland, and one from Sardinia, there could be a connection with ancient Rome. U6d1b(3,895YBP) has two clades represented by single individuals, one from Sicily and one from Morocco. The third clade of U6d1 is unnamed and is represented by a single sample from Portugal and I'll call it U6d1c. U6d1 probably migrated to Europe around 3,000-2,000 years ago, and somehow made its way to Sicily, Sardinia, Ireland, England, and Portugal. U6d3a(2,585YBP) has two Iberian clades and one Moroccan clade, and probably arrived in historical times, possibly along with U6d1. I think U6d1a arrived in Europe from north Africa over 2,000 years ago and was spread by the Romans, U6d1b arrived in Sicily from north Africa sometime during historical times possibly during the classical period, and U6d1c arrived in Portugal from north Africa sometime after 6,000 years ago.

U6c1a(1,287YBP) is an Italian subclade of north African U6c1, and probably arrived in Italy in historical times along with U6c1c(1,287YBP) which has a clade from Spain. U6c2(6,281YBP) has a clade with a single representative from France I'll call U6c2d along with three north African clades, and there are many possible times it arrived in France, I think it might have arrived in historical times with U6c1a and U6c1c

U6a9(name given by me), which is a subclade of U6a2'3'8 is represented by a single Russian sample, and it is really hard to say when its ancestral form arrived, maybe in Palaeolithic times.

Migrations to Sub Sahara Africa

Nearly all U6 in Sub Sahara Africa is descended of very ancient migrations from northwest Africa that occurred mainly between 14,000-8,000 years ago. Northwest African-European U6 subclades U6c, U6d, U6b1, U6b2, U6a1, U6b1, U6a7, U6a6 are pretty much completly absent from Sub Sahara Africa. Below are the time periods i think U6 subclades found in complete U6 squences from Sub Sahara Africa arrived in Sub Sahara Africa. I inbolded haplogroups that I put in more than one section.

U6a2a1(east Africa, very certain), U6a2b(east Africa, very certain), U6a3g(west Africa, very certain), U6a3f(west Africa, pretty certain), U6a3c(west Africa, not very certain), U6a3z(west Africa, not very certain), U6a5b(somewhat certain), U6a5c(west Africa, not veery certain), U6b4(west Africa, pretty certain), U6b6(west Africa, pretty certain), U6b7(west Africa, pretty certain)

12,000-8,000YBP: U6a3f(west Africa, pretty certain), U6a3c(west Africa, pretty certain), U6a3z(west Africa, not very certain), U6a5b(west Africa, very certain), U6a5c(west Africa, somewhat certain)

4,000YBP-present: U6b3(west Africa, very certain), U6d2(east Africa, very certain), U6a7a1*(west Africa, very certain), U6a5a2(west Africa, somewhat certain).

Hard to say: U6a8a(last 9,000 years), U6a5a2(last 9,000 years), U6a7a1*(west Africa, last 5,000 years), U6a10(last 26,000 years)

There are two unnamed basal clades of U6a with single representatives one from Morocco and one from Burkina Faso(I call it U6a10). The clade from Burkina Faso might have a Palaeolithic origin there going back some 20,000 years.

U6a2 reveals Palaeolithic migrations from the Maghreb to sub Sahara Africa, from probably over 12,000 years ago, and possibly as far back as 20,000 years. Clades U6a2a1(12,677YBP) and U6a2b(8,567YBP) originated in East Africa, and U6a2 takes up the majority of Sub Saharan U6. U6a3c(3,895YBP), U6a3f(6,549YBP), U6a3g(has a clade dated as 14,766YBP), and an unnamed clade with no age estimate I'll call U6a3z all originated in west Africa. It would make sense they all migrated together over 15,000 years ago but it is possible they came at differnt times, and the youngest would be U6a3c's ancestral form arriving over 4,000 years ago.

U6a5b(7,219YBP) originated in west Africa and an unnamed U6a5 subclade I'll call U6a5c(no age estimate given)has a single representative from Lake Chad. There is also a subclade of U6a5a(8,567YBP) which has a single representative from Nigeria that I'll call U6a5a2. The ancestral form of U6a5b likely arrived in west Africa 8,000-12,000 years ago, the same could also be true for U6a5c and U6a5a2.

North african haplogroup U6b3(3,893YBP) has a subclade with one representative from Ghana, and it probably descends of recent 4,000-present migration from north Africa to west Africa. There are three unnamed U6b(12,530YBP) subclades with single representatives from west Africa and one unnamed U6b subclade with a single representative from Sudan, they all could have arrived at many differnt times,. I think there is a good chance they are descended of early migrations maybe as far back as 10,000-12,000 years ago.

North African haplogroup U6d2(2,585) has an unnamed subclade with a single representative from Ethiopia and it probably descends from a north African that occurred in historical times. There is a Mauritanian U6a7a1* sample and may be descended of migrations from north Africa that must have occurred in the last 5,000 years.

There is subclade of U6a8a with a single representative from Mauritania. The mother clade U6a8 is estimated to be 8,793 and without a doubt originated in northwest Africa, so U6a8a must have migrated to west Africa sometime after 9,000 years ago.