Four-dimensional region-based PCA of mtDNA haplogroup profiles in Europe and the Near East. Haplogroups and subhaplogroups included in the PCA are as follows: H (excluding H5), H5, HV0 (including HV0*, HV0a, and V), HV (including HV1 but excluding H and HV0), R0a, U1, U2, U3, U4, U5a, U5b, U6, U7, U8, K, U* (represented mainly by U9), J, T1, T2, X, N1 (represented mainly by I), N2 (represented mainly by W), M, and sub-Saharan L. The size of the circles represents the remaining axes (4–24) and is inversely proportional to the error associated with the projection of each population on the first three PCs. The numbers of subjects and haplogroup frequencies for each population are provided in .