[1][2] Studies based on bi-allelic markers of the NRY (non-recombining region of the Y-chromosome) have shown the three main ethnic groups of Bosnia and Herzegovina (Bosniaks, Bosnian Serbs and Bosnian Croats) to share, in spite of some quantitative differences, a large fraction of the same ancient gene pool distinct for the region.
[7][8][9] In 2019 and 2021 studies of late medieval stećak archaeological necropolises Kopošići near Ilijaš and Divičani near Jajce, six samples belonged to Y-DNA haplogroup I2a1b3 (with DYS448=19) and one to R1a.
[12] In 2021 study of medieval samples from the Travnik area, all eight belonged to J2a,[13][14] showing close kinship and same paternal lineage by haplotype and haplogroup.
[1] The frequency of haplogroup I2, especially its subclade I2-CTS10228 and its variance, peaks over a large geographic area covering Bosnia and Herzegovina, Croatia, Serbia, Montenegro, North Macedonia, Albania, Bulgaria, Romania, Moldova, Slovakia, Ukraine, Belarus, Poland and western Russia.
In comparison to older research which argued a prehistoric autochthonous origin of the haplogroup I2 in western Balkans,[1][17][nb 1] the most recent research by O. M. Utevska (2017) found the haplogroups STR haplotypes have the highest diversity in Ukraine, with ancestral STR marker result DYS448=20 comprising "Dnieper-Carpathian" cluster (modal Y-STR for I2-CTS10228>S17250), while younger derived result DYS448=19 (modal Y-STR for I2-CTS10228>S17250>PH908) comprising the "Balkan cluster" which is predominant among the South Slavs,[23][full citation needed] but can also be found in East and West Slavic populations.
[24] The clusters divergence and gradual expansion from the Carpathians in the direction of the Balkan peninsula happened approximately 2,860 ± 730 years ago, coinciding with the Slavic migration.
The huge differentiation between Bosnian and Slovene samples of mtDNA subclusters that are also observed in Central and Eastern Europe, may suggests a broader genetic heterogeneity among the Slavs that settled the Western Balkans during the early Middle Ages.