Haplogroup U3 is primarily a Near Eastern and Caucasian lineage, being found only at a frequency exceeding 3% in the eastern Mediterranean and in the Caucasus. The highest percentages of U3 are observed in Jordan (15%), Syria (5%), Lebanon (5%), Cyprus (5%), Iraq (5%), Armenia (5%), Georgia (4.5%), Azerbaijan (3.5%), Turkey (3.5%), Greece (3.5%) and Egypt (3%), as well as among the various ethnic groups of the North Caucasus, including the Karachay-Balkars (7.5%), Adyghe-Kabardin (7%), Chechen-Ingush (6%), Kumyks (6%), Nogays (4.5%), and North Ossetians (3.5%).
In Europe, apart from Greece, the highest frequencies are found in Italy (2%), and particularly in Liguria (6%), Campania (5%) and Calabria (4%), in Bulgaria (2%), Belarus (2%), Latvia (2%), as well as in specific regions within larger countries such as Brittany (2.5%), Catalonia (2.5%) and Asturias (2%). U3 is almost completely absent from Finland, Scandinavia, the Netherlands, Wales, and interestingly also Sardinia (despite the high level of Near Eastern ancestry among Sardinians). It is also very rare in the Maghreb, Albania or among the Druzes in the Levant, all populations with strong links to Near Eastern Neolithic farmers.
Distribution of mtDNA haplogroup U3 in Europe, North Africa and the Middle East
Origins & History
Haplogroup U3 originated over 30,000 years ago, in all likelihood among Middle Eastern nomadic hunter-gatherers. The U3a subclade is thought to have arisen some time between 18,000 and 26,000 years ago, a period corresponding to the Last Glacial Maximum (LGM).
Haplogroup U3 was present in Pre-Pottery and Early Neolithic Turkey, as well as in Chalcolithic Israel and Iran, and in Bronze Age Armenia, all regions that have high levels of U3 today. However, only a small minority of U3 has been found among the hundreds of Neolithic samples from Europe. Only six of them were identified so far, in the Starčevo culture in Hungary, the Linear Pottery culture (LBK) and the Salzmünde culture in Germany. Those whose subclade has been tested all belonged to U3a, including one U3a1. Overall haplogroup U3 showed up in less than 1% of the hundreds of Neolithic mtDNA tested. The small founding population of early agriculturalists that left Anatolia to colonise Europe may not have had much haplogroup U3 simply by chance. This is a typical founder effect.
Haplogroup U3 has so far been absent from all Mediteranean or West European Neolithic samples. Nowadays U3 is not found in the Sardinian population, which is the best modern proxy for Mediteranean Neolithic farmers.
The only oldest reported U3 sample in Mediteranean Europe (tested by Gomez-Sanchez et al. 2014) at the moment is an individual from the Burgos region in northern Spain dating from the late Chalcolithic period (2,400 BCE). However only the HVR1 region was tested for that sample and yielded a single mutation, which cannot confirm with 100% certainty that that individual was indeed U3.
The presence of U3 in Spain 4,400 years ago could be attributed to a separate Neolithic expansion from the Levant or the Arabian peninsula reaching Iberia through North Africa. These would have been essentially goat herders belonging to Y-haplogroups J1 and T1a (see also Correlating the mtDNA haplogroups of the original Y-haplogroup J1 and T1 herders ).
It is noteworthy that not a single U3 was identified among the numerous Bronze Age individuals tested from Europe and Central Asia, which strongly indicates that U3 was not found among the Indo-European invaders either. Its first appearance in eastern Europe after the Neolithic is a U3b Thracian sample from Bulgaria dated c. 800-500 BCE.
U3a1 is an almost entirely European subclade, and has a coalescence age of approximately 5,000 to 7,000 years before present, suggesting a Neolithic expansion. U3b is the main Middle Eastern and Caucasian subclade. It is also found in Italy, central and eastern Europe, including among the Romani people (Gypsies).
One possible theory for the diffusion of U3, and particularly U3b, to southern Europe is that it was brought from Anatolia to Italy by the (Ionian) Greeks and Etruscans, then spread with the Roman colonisation. The equally recent expansion and scattered presence of U3a1 from the Canary Islands and Ireland to central and eastern Europe is more difficult to explain.
- U3a : found in in most of Europe, in the Caucasus (Georgia) and Central Asia (Afghanistan, Kyrgyzstan, Tajikistan) / found in Neolithic Germany
- U3a1 : found in Neolithic Germany
- U3a1a : found in the British Isles, Norway, Poland, Lithuania, Belarus, Russia and Finland
- U3a1b : found in the Canaries, Austria and Poland
- U3a1c : found in the British Isles (especially Ireland)
- U3a2 : found in Yemen, Italy, Switzerland and Britain / found in the Kura-Araxes culture (Copper Age Armenia)
- U3a3 : found in Georgia
- U3c : found in Azerbaijan, Cyprus and Italy
- U3b1 : found in central Europe and Russia (Volga)
- U3b1a : found in Yemen
- U3b1c : found among Gypsies
- U3b2 : found in Hungary, Sicily, Kurdistan (Turkey), the Levant and the Arabian peninsula
- U3b2a : found in central Italy, Turkey and Armenia
- U3b3 : found in Saudi Arabia and Germany
Associated medical conditions
The common C150T mutation, found in many haplogroups and subclades, has been found at strikingly higher frequency among Chinese and Italian centenarians and may be advantageous for longevity and resistance to stress according to Chen et al. (2012). Haplogroup U3 is defined by the C150T mutation, which means that all U3 members carry this mutation.
The T16189C polymorphism, defining the U3a3 subclade, has been found to lower the rate of mtDNA replication and consequently the number of mtDNA copies, thus reducing metabolic efficiency. It has been linked to maternally inherited thinness (Parker 2005), thinness at birth (Soini 2012) and increased body mass index (Liou 2007), and increased frequency of type 2 diabetes in the UK (Poulton 2002) and in Asia (Weng 2005 and Park 2008).
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