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Haplogroup U4 (mtDNA)

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Geographic distribution

Haplogroup U4 is found at a frequency ranging from 2% to 6% in most regions of Europe. Its highest frequency is observed among the Chuvash (16.5%), Bashkirs (15%) and Tatars (7%) of the Volga-Ural region of Russia, followed by Latvia (8.5%), Georgia (8.5%), Serbia (7%), and southern Daghestan (6.5%). Generally speaking, U4 is more common in Baltic and Slavic countries and around the Caucasus than anywhere else. Within Europe U4 is rarest in fringe regions such as Ireland (1.5%), Portugal (1.5%), north-west Spain (0.5%, except Cantabria which has 3%), Finland (1%), and especially among the Welsh, Sardinians and Saami, where it is completely absent. U4 is not found in countries or regions that lack the paternal lineage R1a, with which it seems to be intimately linked.

Outside Europe and the Caucasus, U4 is found especially in Iran (3%) and throughout Central Asia, particularly in Kyrgyzstan (3%), Turkmenistan (3%), Uzbekistan (2.5%) and Kazakhstan (2%), but also in parts of Siberia, notably in the Altai Republic (5%) and among the speakers of the Khanty and Mansi languages (12%), east of the Ural mountains. U4 is also found at high frequencies in some ethnic groups in Pakistan and Afghanistan, including among the Balochi (2.5%), Hunza Burusho (4.5%), Hazaras (8%), Parsi (13.5%) and especially among the Kalash (34% according to Quintana-Murci et al. 2004), although these frequencies have to been taken cautiously as they are based on very small sample sizes.

Haplogroup U4 rarely exceeds 2% of the population of the Middle East and is completely absent from the Druzes of Syria, Lebanon and Palestine. U4 is only found at trace frequencies in North Africa.

Distribution of mtDNA haplogroup U4 in Europe, North Africa and the Middle East

Distribution of mtDNA haplogroup U4 in Europe, North Africa and the Middle East

Origins & History

Haplogroup U4 originated approximately 25,000 years ago, during the Last Glacial Maximum (LGM). U4 appears to have been a relatively common lineage among Mesolithic European hunter-gatherers. It was identified in skeletons from Mesolithic Russia (including some U4a1 samples), Lithuania, Sweden, Germany and Portugal. Based on the small number of Mesolithic samples tested to date, U4 seems to have been much more common in Northeast Europe than elsewhere. This would make sense since it correlates strongly with Y-haplogroup R1a nowadays.

During the Neolithic period U4 stands out by its absence from the hundreds of samples tested to date, except for one Late Neolithic/Chalcolithic sample (c. 3250 BCE) from Catalonia and one from Portugal (3000 BCE). Along with Cantabria, Catalonia and Portugal also happen to be the regions of Iberia where U4 is the most common today. As there appears to be a continuity in these regions since the Mesolithic, it is possible that Iberian U4, or West European U4 in general, was brought by nomadic tribes of hunter-gatherers belonging to old, pre-Indo-European subclades of R1a, such as SRY1532.2 or M17. Originally from eastern Europe, these R1a/U4 people would have crossed all Europe and survived in isolated pockets of western Europe from the Neolithic onwards.

U4 and the Bronze & Iron Age Indo-Europeans

Haplogroup U4 make a strong come back during the Bronze Age, where it is found at high frequency among remains from the Proto-Indo-European Corded Ware culture and Catacomb culture (a staggering 25% of the 28 samples, see Wilde et al. 2014)), both associated with the diffusion of R1a to Central Europe and Scandinavia, and in the Unetice culture, thought to be the first predominantly R1b culture around what is now Germany. The subclades identified for the Corded Ware and Unetice cultures were respectively U4a1 and U4c1. Both of these subclades are also found in Central Asia today, confirming the Indo-European connection.

U4 was also found in the Yamna culture, the presumed homeland of Proto-Indo-European speakers in the Pontic Steppe. The Volga-Ural region played a major role in Bronze Age PIE cultures, and remained fairly isolated from the subsequent population movements within Europe. The same is true for the central Caucasus region, such as Georgia and southern Daghestan, which received relatively little influx of foreign genes after the Bronze Age. The fact that U4 is many times more prevalent in these regions today also suggest a higher frequency among Bronze Age PIE speakers. During the Yamna and Maykop periods (3700-2500 BCE), R1a and R1b people would have intermingled in Pontic-Caspian Steppes and North Caucasus, explaining why U4 is also found among R1b populations, although at a lower frequency than among R1a populations. In modern France and northern Italy, the percentage of U4 looks directly proportional to the frequency of combined haplogroups R1a and R1b.

Interesting, Fernández et al. (2005) also found two U4 individuals (including one U4a2b) in Sumerian city of Mari in Syria dating from the Early Dynastic Period (2900-2700 BCE), just after the Uruk collapse, which could have been caused by early Indo-European incursions into the Near East.

U4 maternal lineages were found in Bronze Age cultures associated with the Indo-European migrations in Central Asia and Siberia, such as the Andronovo and Karasuk cultures (Keyser 2009), but also in in the Tarim basin in north-west China during the Early Iron Age (Zhang 2010).

Subclades

  • U4
    • U4a
      • U4a1: found in northern and central Europe, Cantabria, in Central Asia (Kyrgyzstan, Turkmenistan, Uzbekistan), Iran, Pakistan (Kalash, Balochi) and India
        • U4a1a: found mostly in Scandinavia, Germany and Poland
          • U4a1a1: found in Poland and Russia
        • U4a1b: found in Poland
          • U4a1b1: found in Slovakia, Germany, Switzerland and Britain
        • U4a1c: found in central Europe
        • U4a1d: found in Russia, including northern Siberia (Nganasan)
      • U4a2: found in northern and central Europe, as well as in Central Asia (Kyrgyzstan, Turkmenistan, Uzbekistan)
        • U4a2a: found in Lithuania, Poland, Slovakia, Germany, Scandinavia, Iran (Qashqai) and Central Asia (Kyrgyzstan)
          • U4a2a1
        • U4a2b: found mostly in central Europe and Russia, but also in Scandinavia and the Netherlands
        • U4a2c
          • U4a2c1
        • U4a2d: found in Ukraine and the British Isles
        • U4a2e: found in Poland
        • U4a2f
        • U4a2g: found in Russia
        • U4a2h: found in Britain
      • U4a3: found in Poland, Germany Switzerland, Denmark, Belgium and England
    • U4b
      • U4b1
        • U4b1a
          • U4b1a1: found in Norway, Iceland and Central Asia (Kyrgyzstan, Tajikistan)
            • U4b1a1a: found in Germany and Italy
              • U4b1a1a1: found in the northeast Caucasus, Iran (Persians), central Europe, France and Italy
          • U4b1a2: found in the British Isles and Norway
            • U4b1a2a: found in Poland
          • U4b1a3
            • U4b1a3a: found in Poland, Germany and Italy
          • U4b1a4: found in the Altai (Tubalar)
        • U4b1b
          • U4b1b1: found in Lithuania, Germany, the British Isles and northern Turkey
            • U4b1b1a: found in the British Isles
      • U4b2: found in Scandinavia and Pakistan (Hunza Burusho)
        • U4b2a: found in France
          • U4b2a1: found in central Europe, Denmark, Ireland and Cantabria
      • U4b3: found in Russia, Greece and Austria
    • U4c
      • U4c1: found in most of Europe as well as in Iran (Persians) and in Central Asia (Turkmenistan, Uzbekistan)
        • U4c1a: found in most of Europe, but also in Iran (Persians) and Siberia
      • U4c2
        • U4c2a: found in Poland and the British Isles
    • U4d
      • U4d1: found in Russia, Baltic countries, Poland, Czechia, Germany, the Netherlands and Scandinavia
        • U4d1a
          • U4b1d1a1: found in Germany, Sweden and especially Finland
        • U4d1b: found in Poland
      • U4d2: found in central Europe and the northern Siberia (Nganasan)
      • U4d3: found in Ukraine, Germany, and the British Isles

Associated medical conditions

Rollins et al. (2009) examined the association between brain pH and mtDNA alleles. The highest brain pH was found in members of haplogroups U and K. Higher pH confers protection against Parkinson's disease and psychiatric disorders such as schizophrenia, bipolar disorder, and major depressive disorder. Another study by the University of Manchester suggests that a lower brain acidity (i.e. higher pH) has a protective effect against strokes. Research on intelligence point that people with higher IQ tend to have more alkaline brains. Higher pH is associated with better conductivity-transmission between neurons (source).

Hendrickson et al. (2008) studied the role played by mitochondrial function in AIDS progression in HIV-1 infected persons. They found that AIDS progression was slower for members of haplogroups H3, I, K, U, W and X.

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