The initial peopling of the Americas: A growing number of founding mitochondrial genomes from Beringia

Pan-American mitochondrial DNA (mtDNA) haplogroup Cl has been recently subdivided into three branches, two of which (Clb and Clc) are characterized by ages and geographical distributions that are indicative of an early arrival from Beringia with Paleo-lndians. In contrast, the estimated ages of Cld-the third subset of Cl-looked too young to fit the above scenario. To define the origin of this enigmatic Cl branch, we completely sequenced 63 Cld mitochondrial genomes from a wide range of geographically diverse, mixed, and indigenous American populations. The revised phylogeny not only brings the age of Cld within the range of that of its two sister clades, but reveals that there were two Cld founder genomes for Paleo-Indians. Thus, the recognized maternal founding lineages of Native Americans are at least IS, indicating that the overall number of Beringian or Asian founder mitochondrial genomes will probably increase extensively when all Native American haplogroups reach the same level of phylogenetic and genomic resolution as obtained here for ad.