Overview
Haplogroup R-Y13227 is one of the early diverging branches within the upstream R-PF6135 cluster, representing a stage of the haplogroup R phylogeny that predates the formation of both the R1 and R2 macrolineages. Y13227 emerged during a pivotal period of Eurasian prehistory when anatomically modern humans were adapting to colder climates, expanding into the northern steppe and forest steppe zones, and experiencing repeated demographic bottlenecks that drastically reduced and re-shaped paternal diversity. Y13227 likely belonged to Upper Paleolithic groups that ranged between the Caspian steppe corridor and southwestern Siberia, populations that formed the demographic bridge between early West Eurasian ancestry and the ancestors of later R bearing groups. The extremely deep age of Y13227 and the absence of extensive downstream branches suggest that it survived in a small, isolated cluster that never participated in the large demographic expansions which later characterized R1a and R1b during the Bronze Age. Although extremely rare in modern populations, Y13227 provides important clues about the structure of early West Eurasian males before the migrations associated with the Yamnaya horizon and later Indo European expansions. Occasionally, ancient genomes from early Eurasian contexts exhibit SNP profiles upstream of Y13227, demonstrating that this lineage once belonged to a broader Paleolithic genetic framework.