High prevalence of haplogroup I with its sublineage I2a (43.13%) was expected, when considering previously published literature (Marjanović et al., 2005; Dogan et al., 2016a). In three main ethnic groups in B&H, I2a accounted for 71% of all haplogroups in Croats, 44% in Bosniaks, and 31% in Serbs (Marjanović et al., 2005) based on Y-SNP analysis. In the previous study of Croatian and Serbian populations, sublineage I2a was also the most frequent (Barać et al., 2003; Peričić et al., 2005; Kačar et al., 2019). Paleolithic origin of this haplogroup suggests the possibility of modern population expansion from one of the post-Glacial refuges into the rest of the Balkan Peninsula (Marjanović et al., 2006). It is believed that haplogroup I arrived in the area of Balkan Peninsula around 25,000 years ago from the Middle East through Anatolia (Battaglia et al., 2009; Primorac et al., 2011). However, recent insights into this research area suggest the possibility of this haplogroup being associated with more recent population movements; however, this requires additional analyses (Marjanović et al., 2019). In comparison to other European populations, I2a could be considered a typical Southeast European haplogroup (Kushniarevich et al., 2015).
Haplogroup R, with its major sublineage R1a, was the second most abundant in the study population of B&H with frequency of 14.79%. In the previous Y-SNP-based study, the haplogroup R accounted for around 14% of all Y chromosomes with an even distribution among three ethnic groups, namely 15% in Bosniaks, 14% in Serbs, and 12% in Croats (Marjanović et al., 2005). In the total Serbian population, haplogroup R was found in a frequency of 15.9%, while it was shown to be more common in Croatia accounting for a total of 33.9% in the mainland population. In the Slovenian population, the prevalence of this haplogroup was 37% (Barać et al., 2003; Peričić et al., 2005; Kačar et al., 2019). Theories on R1a origins suggest the flow of haplogroup R from West Asia into the Balkan region as a post-Last Glacial Maximum (LGM) event, that is, during the Mesolithic time (Myres et al., 2011; Primorac et al., 2011). The connection between haplogroups I and R was described through migration and gene flow between Europe and Middle East using both autosomal and Y-chromosomal markers (Kovačević et al., 2014).
