Haplogroup I (M170) is a Y-chromosome DNA haplogroup. It is a subgroup of haplogroup IJ, which itself is a derivative of the haplogroup IJK. Subclades I1 and I2 can be found in most present-day European populations, with peaks in some Northern European and Southeastern European countries.

Haplogroup I most likely arose in Europe, with it so far found in Palaeolithic sites throughout Europe, but not outside it. It diverged from common ancestor IJ* about 43,000 years ago. Early evidence for haplogroup J has been found in the Caucasus and Iran. In addition, living examples of the precursor Haplogroup IJ* have been found only in Iran, among the Mazandarani and ethnic Persians from Fars. This may indicate that IJ originated in South West Asia.

The oldest example found was originally that of Paglicci133 from Italy, which is at least 31,000 years old, however, in a later study this was changed, and instead Dolní Věstonice (DV14) from the Czech Republic was reported as the oldest, being at least 30,800 years old.

Haplogroup I has been found in multiple individuals belonging to the Gravettian culture. The Gravettians expanded westwards from the far corner of Eastern Europe, likely Russia, to Central Europe. They are associated with a genetic cluster that is normally called the Věstonice cluster.

Origins

Available evidence suggests that I-M170 was preceded into areas in which it would later become dominant by haplogroups K2a (K-M2308) and C1 (Haplogroup C-F3393). K2a and C1 have been found in the oldest sequenced male remains from Western Eurasia (dating from circa 45,000 to 35,000 years BP), such as: Ust'-Ishim man (modern west Siberia) K2a*, Oase 1 (Romania) K2a*, Kostenki 14 (south west Russia) C1b, and Goyet Q116-1 (Belgium) C1a.Seguin-Orlando et al. (2014)「structure in Europeans dating back at least 36,200 years」 The oldest I-M170 found is that of an individual known as Krems WA3 (lower Austria), dating from circa 33,000-24,000 BP. At the same site, two twin boys were also found, both were assigned to haplogroup I*.

Haplogroup IJ was in the Middle East and/or Europe about 40,000 years ago. The TMRCA (time to most recent common ancestor) for I-M170 was estimated by Karafet and colleagues in 2008 to be 22,200 years ago, with a confidence interval between 15,300 and 30,000 years ago. This would make the founding event of I-M170 approximately contemporaneous with the Last Glacial Maximum (LGM), which lasted from 26,500 years ago until approximately 19,500 years ago. TMRCA is an estimate of the time of subclade divergence. Rootsi and colleagues in 2004 also note two other dates for a clade, age of STR variation, and time since population divergence. These last two dates are roughly associated, and occur somewhat after subclade divergence. For Haplogroup I-M170 they estimate time to STR variation as 24,000 ±7,100 years ago and time to population divergence as 23,000 ±7,700 years ago. These estimates are consistent with those of Karafet 2008 cited above. However, Underhill and his colleagues calculate the time to subclade divergence of I1 and I2 to be 28,400 ±5,100 years ago, although they calculate the STR variation age of I1 at only 8,100 ±1,500 years ago.P.A. Underhill, N.M. Myres, S. Rootsi, C.T. Chow, A.A. Lin, R.P. Otillar, R. King, L.A. Zhivotovsky, O. Balanovsky, A. Pshenichnov, K.H. Ritchie, L.L. Cavalli-Sforza, T. Kivisild, R. Villems, S.R. Woodward, New Phylogenetic Relationships for Y-chromosome Haplogroup I: Reappraising its Phylogeography and Prehistory, in P. Mellars, K. Boyle, O. Bar-Yosef and C. Stringer (eds.), Rethinking the Human Evolution (2007), pp. 33–42.

Semino (2000) speculated that the initial dispersion of this population corresponds to the diffusion of the Gravettian culture. Later the haplogroup, along with two cases of Haplogroup C, was found in human remains belonging to the previously mentioned Gravettian culture and in individuals of the Magdalenian and Azilian cultures. Rootsi and colleagues in 2004 suggested that each of the ancestral populations now dominated by a particular subclade of Haplogroup I-M170 experienced an independent population expansion immediately after the Last Glacial Maximum.

The five known cases of Haplogroup I from Upper Paleolithic European human remains make it one of the most frequent haplogroup from that period. In 2016, the 31,210–34,580-year-old remains of a hunter-gatherer from Paglicci Cave, Apulia, Italy were found to carry I-M170. So far, only Haplogroup F* and Haplogroup C1b have been documented, once each, on older remains in Europe. I2 subclade of I-M170 is the main haplogroup found on male remains in Mesolithic Europe, until circa 6,000 BCE, when mass migration into Europe of Anatolian farmers carrying Y-DNA G2a happened.

Due to the arrival of so-called Early European Farmers (EEFs), I-M170 is outnumbered by Haplogroup G among Neolithic European remains and by Haplogroup R in later remains.

The earliest documentation of I1 is from Neolithic Hungary, although it must have separated from I2 at an earlier point in time.

In one instance, haplogroup I was found far from Europe, among 2,000-year-old remains from Mongolia.

It would seem to be that separate waves of population movement impacted Southeastern Europe. The role of the Balkans as a long-standing corridor to Europe from Anatolia and/or the Caucasus is shown by the common phylogenetic origins of both haplogroups I and J in the parent haplogroup IJ (M429). This common ancestry suggests that the subclades of IJ entered the Balkans from Anatolia or the Caucasus, some time before the Last Glacial Maximum. I and J were subsequently distributed in Asia and Europe in a disjunctive phylogeographic pattern typical of "sibling" haplogroups. A natural geographical corridor like the Balkans is likely to have been used later by members of other subclades of IJ, as well as other haplogroups, including those associated with Early European Farmers.

The existence of Haplogroup IJK – the ancestor of both haplogroups IJ and K (M9) – and its evolutionary distance from other subclades of Haplogroup F (M89), supports the inference that haplogroups IJ and K both arose in Southwestern Asia. Living carriers of F* and IJ* have been reported from the Iranian Plateau.

Distribution Frequencies of Haplogroup I: Population% hg I% hg I (Subpopulation)Sampled individualsSource Abazinians3.488Sergeevich 2007ИЗУЧЕНИЕ ГЕНЕТИЧЕСКОЙ СТРУКТУРЫ НАРОДОВ ЗАПАДНОГО КАВКАЗА ПО ДАННЫМ О ПОЛИМОРФИЗМЕ Y-ХРОМОСОМЫ, МИТОХОНДРИАЛЬНОЙ ДНК И ALU-ИНСЕРЦИЙ Abkhazians33.312Nasidze Ivan 2004 Adyghe (Adygea)7154Yunusbayev 2011 Adyghe (Cherkessia)2126Sergeevich 2007 Adyghe (Kabardia)1059Nasidze Ivan 2004 Afghanistan 3 (Hazara people)60El Sibai 2009 Afghanistan 1.5% 3.3% (2/60) Hazara, 1.8% (1/56) Tajik 204 Haber et al. 2012 Afghanistan 0.99% 2.6% (2/77) Hazara, 2.1% (3/142) Tajiks, 0/74 Turkmens, 0/87 Pashtuns, 0/127 Uzbeks 507 Di Cristofaro 2013Afghan Hindu Kush: Where Eurasian Sub-Continent Gene Flows Converge Albanians 13% (29/223) (Albania)223Sarno 2015 Albanians 16 (Tosk), 4 (Gheg)Ferri 2010 Albanians 21.82% (12/55) (Tirana)55Battaglia 2008 Albanians 7 (Tirana)30Bosch 2006 Algerians 0156Introducing the Algerian Mitochondrial DNA and Y-Chromosome Profiles into the North African Landscape Andis27 Armenians 5FTDNA 2013 Avars2115Balanovsky Austrians 28 50 (Vienna), 29 (Graz), 6 (Tyrol) Ashkenazi 1 1099 Azeri3 72Nasidze Ivan 2004 Balkars3135Kutuev 2007Кутуев Ильдус Альбертович. Генетическая структура и молекулярная филогеография народов кавказа Belarusians 23 11 (West), 15 (North), 16 (East), 28 (Centre), 30 (East Polesie), 34 (West Polesie)565Kushniarevich 2013 Belarusians 32 Polesie- 43 (Vichin), 12 (Avtyuki)204Sergeevich 2015ВКЛАД ОТДЕЛЬНЫХ ПОЛЕССКИХ ПОПУЛЯЦИЙ И ПОПУЛЯЦИИ БЕЛОРУССКИХ ТАТАР В ГЕНОФОНД НАСЕЛЕНИЯ БЕЛАРУСИ Bosnia and Herzegovina 53 73 (Croats), 49 (Bosniaks), 33 (Serbs)256Marjanovic 2006 Bosnia and Herzegovina 65Herzegovina- 71 (Mostar, Siroki Brijeg), Bosnia- 54 (Zenica)210Pericic 2005Bosnia and Herzegovina73 (Croats), 45 (Bosniaks), 36 (Serbs)255Battaglia 2008 Bulgarians 27-29 40 (Varna), 32 (Sofia), 30 (Plovdiv), 10 (Haskovo)935Karachanak 2009–13 Bulgarians 34100Begona Martinez-Cruz 2012 Bulgaria 19 (Bulgarian Turks)63Zaharova 2002 Central Asia 2 984Rootsi 2004 Chechens0330Balanovsky Croats 451100Mrsic 2012 Croats 47 55 (Hvar), 52 (Osijek), 41 (Pula), 57 (Split), 29 (Varaždin)518Primorac 2022 Cyprus 1 164 El-Sibai 2009Geographical Structure of the Y-chromosomal Genetic Landscape of the Levant: A coastal-inland contrast Czechs 18 25 (Klatovy), 25 (Písek), 15 (Brno) 14 (Hradec Králové), 10 (Třebíč) 257 Luca 2007Y-chromosomal variation in the Czech Republic Danes 49 194Rootsi 2004 Darginians58 26Nasidze Ivan 2004 Darginians (Kaitak) 0101 Dutch27.8 2085Altena 2020Altena, E., Smeding, R., van der Gaag, K.J. et al. The Dutch Y-chromosomal landscape. Eur J Hum Genet 28, 287–299 (2020). https://doi.org/10.1038/s41431-019-0496-0 Dutch33 410Van Doorn 2008ZONEN VAN ADAM IN NEDERLAND