The immediate descendants of IJ are Haplogroup I and Haplogroup J. Its sole sibling is K (which includes most of the world's male population).
Haplogroup IJ derived populations account for a significant proportion of the pre-modern populations of Europe (especially Scandinavia and the Balkans), Anatolia, the Caucasus, the Middle East (especially Arabia, Levant and Mesopotamia) and coastal North Africa. As a result of mass migrations during the modern era, they are now also significant in The Americas and Australasia.
Haplogroup I appears to have arisen in Europe, so far being found in Palaeolithic sites throughout Europe (Fu 2016), but not outside it. It diverged from common ancestor IJ* about 43,000 years B.P. (Karafet 2008). Early evidence for haplogroup J has been found in the Caucasus and Iran (Jones 2015, Fu 2016). In addition, living examples of the precursor Haplogroup IJ* have been found only in ethnicities living in modern day Iran. This may indicate that IJ originated in West Asia.
A 2008 estimate suggested that the most recent common ancestor of haplogroup IJ could have lived 30,500–46,200 years ago,[3] while another estimate suggests 43,000–45,700 years.[1]
Examples of the basal/paragroup Haplogroup IJ* (M429) were first reported in a 2012 study of genetic diversity in Iran, by Grugni et al. These individuals were reported to be positive for M429 and negative for the SNPs M170 and M304, which define haplogroup I and haplogroup J respectively. However, because the researchers filtered for relatively few SNPs, these individuals may have carried less well-known SNPs equivalent to M170 and M304.[4][5] Given the limited scope of the testing – and the small number of haplogroup IJ samples that were discovered – few firm conclusions have yet been drawn.
IJ split in a typically disjunctive, almost mutually-exclusive geographical pattern, with J-M304 far more common in the Caucasus, and I-M170 far more common in Europe; the age of IJ and its subclades suggest that IJ probably entered Europe through the Balkans, some time before the last glacial maximum (about 26,500 years BP). The same geographic corridor (the Balkans) also supported later gene flows, including the Early Neolithic Farmers from Anatolia about 9,000 years BP.
I (M170, P19, M258, P38, P212, U179, Haplogroup I notation updated to ISOGG 2008; L41, M170, M258, P19_1, P19_2, P19_3, P19_4, P19_5, P38, P212, U179)
I* (unobserved)
I1 (M253, M307, M450/S109, P30, P40, S62, S63, S64, S65, S66, S107, S108, S110, S111, per ISOGG 2008; also L64, L75, L80, L81, L118, L121/S62, L123, L124/S64, L125/S65, L157.1, L186, L187, L840, M307.2/P203.2) Typical of populations of Scandinavia and Northwest Europe, with a moderate distribution throughout Eastern Europe
I1* (unobserved)
I-CTS12768 (no phylogenetic name as of 2021)
I-CTS12768* – living example in Sweden.
I-Z17954 (no phylogenetic name as of 2021)
I-Z17954* (unobserved)
I-Y21293 – living example in Netherlands.
I-Y19092 – living examples in Normandy and Finland.
I1a – DF29/S438
I1a* - living examples in Sweden, Denmark and Portugal.
I2a (P37.2) (formerly I1b1) Typical of the South Slavic peoples of the Balkans, especially the populations of Bosnia, Croatia, Serbia and Slovenia ; also found with high haplotype diversity values, but lower overall frequency, among the West Slavic populations of Slovakia and the Czech Republic; a node of elevated frequency in Moldavia correlates with that observed for Haplogroup I2a (but not for Haplogroup I1)
I2a*
I2a1 (M423)
I2a1*
I2a1a (P41.2/M359.2) (formerly I1b1a)
I2a2 (M26) (formerly I1b1b) Typical of the population of the so-called "archaic zone" of Sardinia; also found at low frequencies among populations of Southwest Europe, particularly in Castile, Béarn, and the Basque Country
I2b1 (M223, P219/S24, P220/S119, P221/S120, P222/U250/S118, P223/S117) (formerly I1b2a - old I1c) Occurs at a moderate frequency among populations of Northwest Europe, with a peak frequency in the region of Lower Saxony in central Germany; minor offshoots appear in Moldavia and Russia (especially around Vladimir, Ryazan, Nizhny Novgorod, and the Republic of Mordovia), and among speakers of Persian (including Iranians, Hazaras in Afghanistan and Pakistan, and Tajiks in Afghanistan)
I2b1*
I2b1a (M284) (formerly I1b2a1) Generally limited to a low frequency in Great Britain
