Overview
Haplogroup R-PH543 represents one of the deepest surviving branches within the early structure of haplogroup R. Its position in the phylogeny places it immediately downstream of the formation of R-M207, at a time when anatomically modern humans were widely expanding across Eurasia during the Upper Paleolithic. PH543 captures a demographic stage that predates the major bifurcation between R1 and R2, making it crucial for reconstructing the earliest phases of R lineage history. Individuals belonging to PH543 or its upstream ancestral components likely inhabited regions spanning western Central Asia, parts of southern Siberia and possibly the northern Iranian Plateau. The rarity of PH543 in modern populations indicates that this lineage represents a remnant of an ancient genetic landscape. While most R-derived paternal lines expanded dramatically during the Late Upper Paleolithic and early Holocene, PH543 appears to have remained limited in size or became absorbed into larger demographic processes. Its deep time depth suggests that it was part of small, regionally isolated hunter gatherer populations that experienced considerable genetic drift. The downstream diversity is limited, but its existence provides valuable insight into the ancestral diversity of early Eurasian populations. Although modern confirmed cases are extremely rare, scattered observations indicate a weak presence in Central Asia and the Caucasus. These occurrences likely represent survival through isolated lineages rather than large-scale expansions. PH543 serves as a key phylogenetic anchor for understanding the emergence of the larger and more successful R1 and R2 branches that later came to dominate wide sections of Eurasia.