Significant (Z|−4|) admixture signal with a source from ancient Wusun observed in contemporary Bulgarians

We report the presence of significant Central Asian ancestry in both contemporary Bulgarians and in early medieval population from SMC (Saltovo Mayaky Culture). The existence of Chalcolithic-Iran (Hajj-Fruz) and Wusun related ancestral component in contemporary Bulgarians comes as a surprise and sheds light on both migration route and ethnic origins of Proto-Bulgarians. We interpret these results as an evidence for a Central –Asian connection for the tribes, constituting the population of SMC and Kubrat’s Old Great Bulgaria in Pontic steppe from 6th-7th century AD. We identify Central Asian Wusun tribes as carriers of this component on the base from the results from f3 and f4 statistics. We suggest that Wusun-related tribes must have played role (or might have even been the backbone) in what became known as the Hunnic migration to Europe during 3 rd -5 th century AD. Same population must have taken part in the formation of the SMC (Saltovo-Mayaki Culture) and Great Old Bulgarian during 6 th -9 th century AD in Pontic – Caspian steppe. We also explore the genomic origins of Thracians and their relations to contemporary Europeans. We conclude that contemporary Bulgarians do not harbor Thracian-specific ancestry, since ancient Thracian samples share more SNPs with contemporary Greeks and even contemporary Icelanders than with contemporary Bulgarians.