The sequencing of the entire mitochondrial DNA belonging to haplogroup U2d reveals that this clade is defined by four coding-region mutations at positions 1700, 4025, 11893, and 14926. Phylogenetic analysis suggests that western Eurasian haplogroup U2d appears to be a sister clade with the Indo-Pakistani haplogroup U2c. Results of a phylogeographic analysis of published population data on the distribution of haplogroup U2d indicate that the presence of such mtDNA lineages in Europe may be mostly a consequence of medieval migrations of nomadic tribes from the Caucasus and eastern Europe to central Europe.