Overview
Haplogroup R-Y42 is one of the deeper branches within the R-M73 phylogeny and represents an early lineage of forager populations distributed between the southern Siberian forest zone and the steppe margin near the Altai Sayan region. Its formation coincided with increased Holocene forest density and the establishment of migratory cycles tied to riverine and upland ecosystems. Communities carrying Y42 likely practiced seasonal transhumant style mobility long before the emergence of true pastoralism. The internal phylogeny of Y42 is shallow but shows regionally distinct microbranches, reflecting segmentation among isolated forest forager groups who exchanged tools and cultural practices without substantial gene flow. Archaeological layers associated with microlithic traditions, early woodworking, and riverine fishing align closely with Y42's temporal and ecological horizon. These groups maintained considerable stability until the Bronze Age when the arrival of steppe pastoralists introduced new demographic pressures. In the modern era, R-Y42 occurs at very low frequencies across southern Siberia and in isolated parts of northern Mongolia. Its rarity but survival reinforces the view that certain Holocene forager lineages persisted through millennia of demographic transformation by remaining in environmentally sheltered niches.