Overview
Haplogroup R-YP556 is a rare early branch descending from the important upstream lineage R-V45, a pivotal node in the emergence of the entire R phylogeny. YP556 lies on the deep Paleolithic scaffold of haplogroup R, representing a lineage that survived for tens of millennia in small forager populations inhabiting northern Central Asia or the western Siberian transitional zone. Its formation shortly before or during the harsh climatic oscillations of the Last Glacial Maximum indicates the resilience of early R bearing groups in regions with extreme environmental pressures. YP556 is phylogenetically significant because it marks a stage in the tree where the ancestral lineage had not yet committed to either of the later dominant expansions that produced R1a, R1b or the downstream R2 lineages. Instead, YP556 highlights a demographic pathway that diverged early, persisted in isolation and eventually left only faint genetic traces due to later Bronze Age demographic overwriting. Today, YP556 is nearly absent among living populations, but its historical footprint survives in ancient DNA samples carrying upstream V45 related ancestry. These samples often appear in Paleolithic layers of the western Siberian forest steppe or in transitional regions that connected Central Asia with the northern Eurasian refugia.