Haplogroup IJ (M429/P125) is a human Y-chromosome DNA haplogroup, an immediate descendant of Haplogroup IJK (formerly known as Haplogroup F-L15). IJK is a branch of Haplogroup HIJK. 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. Origin A 2008 estimate suggested that the most recent common ancestor of haplogroup IJ could have lived 30,500–46,200 years ago, while another estimate suggests 43,000–45,700 years. Both of the primary branches of haplogroup IJ – I-M170 and J-M304 – are found among modern populations of the Caucasus, Anatolia, and Southwest Asia. This tends to suggest that Haplogroup IJ branched from IJK in West Asia, Caucasus and/or the Middle East. 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. 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. An inference may also be made that both IJ (M429) and its sole sibling, Haplogroup K (M9) diverged from the parent Haplogroup IJK closer to the Caucasus and the Middle East than to East Asia, due to the evolutionary distance of IJK from its direct ancestor, haplogroup HIJK. 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. Phylogeny and distribution IJ (M429, P123,