The quest to explain demographic history during the early part of human evolution has been limited because of the scarce paleoanthropological record from the Middle Stone Age. To shed light on the structure of the mitochondrial DNA (mtDNA) phylogeny at the dawn of Homo sapiens, we constructed a matrilineal tree composed of 624 complete mtDNA genomes from sub-Saharan Hg L lineages. We paid particular attention to the Khoi and San (Khoisan) people of South Africa because they are considered to be a unique relic of hunter-gatherer lifestyle and to carry paternal and maternal lineages belonging to the deepest clades known among modern humans. Both the tree phylogeny and coalescence calculations suggest that Khoisan matrilineal ancestry diverged from the rest of the human mtDNA pool 90,000–150,000 years before present (ybp) and that at least five additional, currently extant maternal lineages existed during this period in parallel. Furthermore, we estimate that a minimum of 40 other evolutionarily successful lineages flourished in sub-Saharan Africa during the period of modern human dispersal out of Africa approximately 60,000–70,000 ybp. Only much later, at the beginning of the Late Stone Age, about 40,000 ybp, did introgression of additional lineages occur into the Khoisan mtDNA pool. This process was further accelerated during the recent Bantu expansions. Our results suggest that the early settlement of humans in Africa was already matrilineally structured and involved small, separately evolving isolated populations. The quest to explain demographic history during the early part of human evolution has been limited because of the scarce paleoanthropological record from the Middle Stone Age. To shed light on the structure of the mitochondrial DNA (mtDNA) phylogeny at the dawn of Homo sapiens, we constructed a matrilineal tree composed of 624 complete mtDNA genomes from sub-Saharan Hg L lineages. We paid particular attention to the Khoi and San (Khoisan) people of South Africa because they are considered to be a unique relic of hunter-gatherer lifestyle and to carry paternal and maternal lineages belonging to the deepest clades known among modern humans. Both the tree phylogeny and coalescence calculations suggest that Khoisan matrilineal ancestry diverged from the rest of the human mtDNA pool 90,000–150,000 years before present (ybp) and that at least five additional, currently extant maternal lineages existed during this period in parallel. Furthermore, we estimate that a minimum of 40 other evolutionarily successful lineages flourished in sub-Saharan Africa during the period of modern human dispersal out of Africa approximately 60,000–70,000 ybp. Only much later, at the beginning of the Late Stone Age, about 40,000 ybp, did introgression of additional lineages occur into the Khoisan mtDNA pool. This process was further accelerated during the recent Bantu expansions. Our results suggest that the early settlement of humans in Africa was already matrilineally structured and involved small, separately evolving isolated populations. IntroductionCurrent genetic data support the hypothesis of a predominantly single origin for anatomically modern humans.1Cann R.L. Stoneking M. Wilson A.C. Mitochondrial DNA and human evolution.Nature. 1987; 325: 31-36Crossref PubMed Scopus (1871) Google Scholar, 2Underhill P.A. Kivisild T. Use of Y chromosome and mitochondrial DNA population structure in tracing human migrations.Annu. Rev. Genet. 2007; 41: 539-564Crossref PubMed Scopus (302) Google Scholar The phylogeny of the maternally inherited mitochondrial DNA (mtDNA) has played a pivotal role in this model by anchoring our most recent maternal common ancestor to sub-Saharan Africa and suggesting a single dispersal wave out of that continent which populated the rest of the world much later.3Mellars P. Going east: New genetic and archaeological perspectives on the modern human colonization of Eurasia.Science. 2006; 313: 796-800Crossref PubMed Scopus (362) Google Scholar, 4Macaulay V. Hill C. Achilli A. Rengo C. Clarke D. Meehan W. Blackburn J. Semino O. Scozzari R. Cruciani F. et al.Single, rapid coastal settlement of Asia revealed by analysis of complete mitochondrial genomes.Science. 2005; 308: 1034-1036Crossref PubMed Scopus (561) Google Scholar, 5Torroni A. Achilli A. Macaulay V. Richards M. Bandelt H.J. Harvesting the fruit of the human mtDNA tree.Trends Genet. 2006; 22: 339-345Abstract Full Text Full Text PDF PubMed Scopus (351) Google Scholar However, despite its importance as the cradle of humanity and the main location of anatomically modern humans for most of their existence, the initial Homo sapiens population dynamics and dispersal routes remain poorly understood.6Mellars P. Why did modern human populations disperse from Africa ca. 60,000 years ago? A new model.Proc. Natl. Acad. Sci. USA. 2006; 103: 9381-9386Crossref PubMed Scopus (435) Google Scholar, 7Hawks J. Wang E.T. Cochran G.M. Harpending H.C. Moyzis R.K. Recent acceleration of human adaptive evolution.Proc. Natl. Acad. Sci. USA. 2007; 104: 20753-20758Crossref PubMed Scopus (332) Google Scholar The potential to use present-day genetic patterns to detect the existence, or lack thereof, of matrilineal genetic structure among early Homo sapiens populations in sub-Saharan Africa is therefore of particular interest.The human mtDNA phylogeny can be collapsed into two daughter branches, L0 and L1′2′3′4′5′6 (L1′5),5Torroni A. Achilli A. Macaulay V. Richards M. Bandelt H.J. Harvesting the fruit of the human mtDNA tree.Trends Genet. 2006; 22: 339-345Abstract Full Text Full Text PDF PubMed Scopus (351) Google Scholar located on opposite sides of its root (Figure 1).8Kivisild T. Shen P. Wall D.P. Do B. Sung R. Davis K. Passarino G. Underhill P.A. Scharfe C. Torroni A. et al.The role of selection in the evolution of human mitochondrial genomes.Genetics. 2006; 172: 373-387Crossref PubMed Scopus (359) Google Scholar, 9Mishmar D. Ruiz-Pesini E. Golik P. Macaulay V. Clark A.G. Hosseini S. Brandon M. Easley K. Chen E. Brown M.D. et al.Natural selection shaped regional mtDNA variation in humans.Proc. Natl. Acad. Sci. USA. 2003; 100: 171-176Crossref PubMed Scopus (774) Google Scholar The L1′5 branch is far more widespread and has given rise to almost every mtDNA lineage found today, with two clades on this branch, (L3)M and (L3)N, forming the bulk of worldwide non-African genetic diversity and marking the out-of-Africa dispersal 50,000–65,000 years before present (ybp)4Macaulay V. Hill C. Achilli A. Rengo C. Clarke D. Meehan W. Blackburn J. Semino O. Scozzari R. Cruciani F. et al.Single, rapid coastal settlement of Asia revealed by analysis of complete mitochondrial genomes.Science. 2005; 308: 1034-1036Crossref PubMed Scopus (561) Google Scholar (Figure 1). Current models, predating the recognition of L0 as sister to L1′5,9Mishmar D. Ruiz-Pesini E. Golik P. Macaulay V. Clark A.G. Hosseini S. Brandon M. Easley K. Chen E. Brown M.D. et al.Natural selection shaped regional mtDNA variation in humans.Proc. Natl. Acad. Sci. USA. 2003; 100: 171-176Crossref PubMed Scopus (774) Google Scholar, 10Maca-Meyer N. Gonzalez A.M. Larruga J.M. Flores C. Cabrera V.M. Major genomic mitochondrial lineages delineate early human expansions.BMC Genet. 2001; 2: 13Crossref PubMed Scopus (263) Google Scholar suggest that the contemporary sub-Saharan mtDNA gene pool is the result of an early expansion of modern humans from their homeland, often suggested to be East Africa, to most of the African continent by exclusively L1 Hg clades, before being overwhelmed by a later expansion wave of L2 and L3 clades dated to 60,000–80,000 ybp.11Forster P. Ice Ages and the mitochondrial DNA chronology of human dispersals: A review.Philos. Trans. R. Soc. Lond. B Biol. Sci. 2004; 359: 255-264Crossref PubMed Scopus (221) Google Scholar, 12Watson E. Forster P. Richards M. Bandelt H.J. Mitochondrial footprints of human expansions in Africa.Am. J. Hum. Genet. 1997; 61: 691-704Abstract Full Text PDF PubMed Scopus (297) Google Scholar A more recent geographically restricted enrichment of the African maternal gene pool was shown to have occurred during the early Upper Paleolithic, when populations carrying mtDNA clades M1 and U6 arrived to north and northeast Africa from Eurasia, hardly penetrating the sub-Saharan portion of the continent, except Ethiopia.13Kivisild T. Reidla M. Metspalu E. Rosa A. Brehm A. Pennarun E. Parik J. Geberhiwot T. Usanga E. Villems R. Ethiopian mitochondrial DNA heritage: Tracking gene flow across and around the gate of tears.Am. J. Hum. Genet. 2004; 75: 752-770Abstract Full Text Full Text PDF PubMed Scopus (200) Google Scholar, 14Olivieri A. Achilli A. Pala M. Battaglia V. Fornarino S. Al-Zahery N. Scozzari R. Cruciani F. Behar D.M. Dugoujon J.M. et al.The mtDNA legacy of the Levantine early Upper Palaeolithic in Africa.Science. 2006; 314: 1767-1770Crossref PubMed Scopus (196) Google Scholar Therefore, the current sub-Saharan mtDNA gene pool is overwhelmingly a rich mix of L0 and L1′5 clades, found at varying frequencies throughout the continent.15Salas A. Richards M. De la Fe T. Lareu M.V. Sobrino B. Sanchez-Diz P. Macaulay V. Carracedo A. The making of the African mtDNA landscape.Am. J. Hum. Genet. 2002; 71: 1082-1111Abstract Full Text Full Text PDF PubMed Scopus (386) Google ScholarThis entangled pattern of mtDNA variation gives an initial impression of lack of internal maternal genetic structure within the continent. Alternatively, it might indicate the elimination of such an early structure because of massive demographic shifts within the continent, the most dominant of which was certainly the recent Bantu expansions and spread of agriculturist style of living.15Salas A. Richards M. De la Fe T. Lareu M.V. Sobrino B. Sanchez-Diz P. Macaulay V. Carracedo A. The making of the African mtDNA landscape.Am. J. Hum. Genet. 2002; 71: 1082-1111Abstract Full Text Full Text PDF PubMed Scopus (386) Google Scholar However, some L(xM,N) clades do show significant phylogeographic structure in Africa, such as the localization of L1c1a to central Africa16Quintana-Murci L. Quach H. Harmant C. Luca F. Massonnet B. Patin E. Sica L. Mouguiama-Daouda P. Comas D. Tzur S. et al.Maternal traces of deep common ancestry and asymmetric gene flow between Pygmy hunter-gatherers and Bantu-speaking farmers.Proc. Natl. Acad. Sci. USA. 2008; 105: 1596-1601Crossref PubMed Scopus (138) Google Scholar or the localization of L0d and L0k (previously L1d and L1k) to the Khoisan people,17Chen Y.S. Olckers A. Schurr T.G. Kogelnik A.M. Huoponen K. Wallace D.C. mtDNA variation in the South African Kung and Khwe-and their genetic relationships to other African populations.Am. J. Hum. Genet. 2000; 66: 1362-1383Abstract Full Text Full Text PDF PubMed Scopus (147) Google Scholar, 18Knight A. Underhill P.A. Mortensen H.M. Zhivotovsky L.A. Lin A.A. Henn B.M. Louis D. Ruhlen M. Mountain J.L. African Y chromosome and mtDNA divergence provides insight into the history of click languages.Curr. Biol. 2003; 13: 464-473Abstract Full Text Full Text PDF PubMed Scopus (124) Google Scholar, 19Tishkoff S.A. Gonder M.K. Henn B.M. Mortensen H. Knight A. Gignoux C. Fernandopulle N. Lema G. Nyambo T.B. Ramakrishnan U. et al.History of click-speaking populations of Africa inferred from mtDNA and Y chromosome genetic variation.Mol. Biol. Evol. 2007; 24: 2180-2195Crossref PubMed Scopus (155) Google Scholar, 20Vigilant L. Stoneking M. Harpending H. Hawkes K. Wilson A.C. African populations and the evolution of human mitochondrial DNA.Science. 1991; 253: 1503-1507Crossref PubMed Scopus (951) Google Scholar in which they account for over 60% of the contemporary mtDNA gene pool. Early studies based on mtDNA control region variation have suggested that Khoisan divergence dates to an early stage in the history of modern humans,18Knight A. Underhill P.A. Mortensen H.M. Zhivotovsky L.A. Lin A.A. Henn B.M. Louis D. Ruhlen M. Mountain J.L. African Y chromosome and mtDNA divergence provides insight into the history of click languages.Curr. Biol. 2003; 13: 464-473Abstract Full Text Full Text PDF PubMed Scopus (124) Google Scholar whereas their anthropological and linguistic features show closer affinities to each other than to those of other populations in Africa.21Barnard A. Hunters and Herders of Southern Africa: A Comparative Ethnography of the Khoisan Peoples. Cambridge University Press, New York1992Crossref Google Scholar, 22Guldemann T. Quotative Indexes in African Languages: A Synchronic and Diachronic Survey. Mouton de Gruyter, Berlin2007Google Scholar Their distinctiveness is also supported by phylogenetic studies of the male-specific Y chromosome that indicate that the most basal branch of the Y phylogeny is now common among the Khoisan but is rare or absent in other populations.18Knight A. Underhill P.A. Mortensen H.M. Zhivotovsky L.A. Lin A.A. Henn B.M. Louis D. Ruhlen M. Mountain J.L. African Y chromosome and mtDNA divergence provides insight into the history of click languages.Curr. Biol. 2003; 13: 464-473Abstract Full Text Full Text PDF PubMed Scopus (124) Google ScholarTo better understand the reason for the high prevalence of two basal mtDNA lineages L0d and L0k within Khoisan, and the possible implications that this pattern might have on our understanding of early maternal genetic structure within Homo sapiens populations, we studied, at the level of complete mtDNA sequences, the variation of 624 Hg L(xM,N) mtDNA genomes. Our findings enable the identification of different phylogenetic origins for L0d and L0k lineages versus all other contemporary mtDNA lineages found within the Khoisan and support a demographic model with extensive maternal genetic structure during the early evolutionary history of Homo sapiens. This maternal structure is likely the result of ancient population splits and movements and is not consistent with a homogenous distribution of modern humans throughout sub-Saharan Africa.Material and MethodsSamplingTable S1 available online details the information for each of the 624 samples included in this study. We evaluated all 315 Hg L(xM,N) complete mtDNA sequences reported in the literature.5Torroni A. Achilli A. Macaulay V. Richards M. Bandelt H.J. Harvesting the fruit of the human mtDNA tree.Trends Genet. 2006; 22: 339-345Abstract Full Text Full Text PDF PubMed Scopus (351) Google Scholar, 8Kivisild T. Shen P. Wall D.P. Do B. Sung R. Davis K. Passarino G. Underhill P.A. Scharfe C. Torroni A. et al.The role of selection in the evolution of human mitochondrial genomes.Genetics. 2006; 172: 373-387Crossref PubMed Scopus (359) Google Scholar, 9Mishmar D. Ruiz-Pesini E. Golik P. Macaulay V. Clark A.G. Hosseini S. Brandon M. Easley K. Chen E. Brown M.D. et al.Natural selection shaped regional mtDNA variation in humans.Proc. Natl. Acad. Sci. USA. 2003; 100: 171-176Crossref PubMed Scopus (774) Google Scholar, 10Maca-Meyer N. Gonzalez A.M. Larruga J.M. Flores C. Cabrera V.M. Major genomic mitochondrial lineages delineate early human expansions.BMC Genet. 2001; 2: 13Crossref PubMed Scopus (263) Google Scholar, 16Quintana-Murci L. Quach H. Harmant C. Luca F. Massonnet B. Patin E. Sica L. Mouguiama-Daouda P. Comas D. Tzur S. et al.Maternal traces of deep common ancestry and asymmetric gene flow between Pygmy hunter-gatherers and Bantu-speaking farmers.Proc. Natl. Acad. Sci. USA. 2008; 105: 1596-1601Crossref PubMed Scopus (138) Google Scholar, 23Ingman M. Kaessmann H. Paabo S. Gyllensten U. Mitochondrial genome variation and the origin of modern humans.Nature. 2000; 408: 708-713Crossref PubMed Scopus (1017) Google Scholar, 24Howell N. Elson J.L. Turnbull D.M. Herrnstadt C. African laplogroup L mtDNA sequences show violations of clock-like evolution.Mol. Biol. Evol. 2004; 21: 1843-1854Crossref PubMed Scopus (29) Google Scholar, 25Behar D.M. Metspalu A. Kivisild T. Rosset S. Tzur S. Hadid Y. Yodkovsky G. Rosengarten D. Pereira L. Amorim A. et al.Counting the founders: The matrilineal genetic ancestry of the Jewish Diaspora.PLoS ONE. 2008; (in press)Google Scholar Next, we identified all Hg L(xM,N) samples in all population sample collections available in Haifa (D.M.B.), Family Tree DNA (D.M.B.), Johannesburg (H.S. and H.M.), National Geographic Society (R.S.W. and J.B.S.), Paris (L.Q.M.), Porto (L.P.), Rome (R.S.), and Tartu (E.M. and R.V.) and chose 309 for complete mtDNA sequencing. Samples were chosen to include the widest possible range of Hg L(xM,N) internal variation on the basis of the previously available sequence analysis of the mtDNA control region and are, therefore, biased toward rare variants. In addition, we attempted to focus on branches (e.g., L0d, L0k), populations (e.g., Khoisan), and geographic regions (e.g., Chad) for which the current data were scant. Last, we preferred to sequence variants that the current literature suggested to be rare or anecdotal in any given geographic region (e.g., L0k in the Near East). All samples reported herein were derived from blood, buccal swab, or blood cell samples that were collected with informed consent according to procedures approved by the Institutional Human Subjects Review Committees in their respective locations.Complete mtDNA SequencingDNA was amplified with 18 primers to yield nine overlapping fragments as previously reported.26Taylor R.W. Taylor G.A. Durham S.E. Turnbull D.M. The determination of complete human mitochondrial DNA sequences in single cells: Implications for the study of somatic mitochondrial DNA point mutations.Nucleic Acids Res. 2001; 29 (E74–E74)Crossref Scopus (12) Google Scholar After purification, the nine fragments were sequenced by means of 56 internal primers to obtain the complete mtDNA genome. Sequencing was performed on a 3730xl DNA Analyzer (Applied Biosystems), and the resulting sequences were analyzed with the Sequencher software (Gene Codes Corporation). Mutations were scored relative to the revised Cambridge Reference Sequence (rCRS).27Andrews R.M. Kubacka I. Chinnery P.F. Lightowlers R.N. Turnbull D.M. Howell N. Reanalysis and revision of the Cambridge reference sequence for human mitochondrial DNA.Nat. Genet. 1999; 23: 147Crossref PubMed Scopus (2521) Google Scholar The 309 Hg L(xM,N) complete mtDNA sequences reported herein have been submitted to GenBank (accession numbers EU092658 – EU092966 ). Sample quality control was assured as follows:1.After the primary polymerase chain reaction (PCR) amplification of the nine fragments, DNA handling and distribution to the 56 sequencing reactions was aided by the Beckman Coulter Biomek FX liquid handler to minimize the chance for human pipetting errors.2.All 56 sequencing reactions of each sample were attempted simultaneously in the same sequencing run and included resequencing of the control region to assure that the correct sample was chosen. Therefore, most observed polymorphisms were determined by at least two sequences. However, in a minority of the cases only one sequence is available because of various technical reasons, usually related to the amount and quality of the DNA available.3.Any fragment that failed the first sequencing attempt or any ambiguous base call was tested by additional and independent PCR and sequencing reactions. In these cases, the first hypervariable segment was again resequenced to assure that the correct sample was chosen.4.Table S1 includes for each sample that needed several genotyping attempts the information regarding fragments26Taylor R.W. Taylor G.A. Durham S.E. Turnbull D.M. The determination of complete human mitochondrial DNA sequences in single cells: Implications for the study of somatic mitochondrial DNA point mutations.Nucleic Acids Res. 2001; 29 (E74–E74)Crossref Scopus (12) Google Scholar that were resequenced to help in the search for DNA handling errors and artificial recombination events.5.All sequences were aligned by the software Sequencher (Gene Codes Corporation), and all positions with a Phred score less than 30 were directly inspected by an operator.28Ewing B. Green P. Base-calling of automated sequencer traces using phred. II. Error probabilities.Genome Res. 1998; 8: 186-194Crossref PubMed Google Scholar, 29Ewing B. Hillier L. Wendl M.C. Green P. Base-calling of automated sequencer traces using phred. I. Accuracy assessment.Genome Res. 1998; 8: 175-185Crossref PubMed Scopus (4846) Google Scholar All positions that differed from the rCRS were recorded electronically to minimize typographic errors.6.Any sample that showed a deviation from the expected evolutionary hierarchy as suggested by the established Hg L(xM,N) phylogeny was highlighted and resequenced when a lab error was suspected.7.Any comments and remarks raised by external investigators after release of the data will be addressed by reobservation of the original sequences for accuracy. After that, any unresolved result will be further examined by resequencing and, if necessary, immediately corrected by publication of an erratum.NomenclatureThe term African Hg L(xM,N) is used to describe all mtDNA Haplogroups but (L3)M and (L3)N. We reserve the term branch to describe the two evolving sides of the root and have labeled them L0 and L1′2′3′4′5′6 (L1′5).5Torroni A. Achilli A. Macaulay V. Richards M. Bandelt H.J. Harvesting the fruit of the human mtDNA tree.Trends Genet. 2006; 22: 339-345Abstract Full Text Full Text PDF PubMed Scopus (351) Google Scholar The two major branches each composed of one to several haplogroups.30Torroni A. Sukernik R.I. Schurr T.G. Starikorskaya Y.B. Cabell M.F. Crawford M.H. Comuzzie A.G. Wallace D.C. mtDNA variation of aboriginal Siberians reveals distinct genetic affinities with Native Americans.Am. J. Hum. Genet. 1993; 53: 591-608PubMed Google Scholar Note that the L0 branch is made of the L0 Hg alone, whereas the L1′5 branch includes haplogroups L1–L6. Haplogroups are composed of clades (e.g., L0d and L0k), which in their turn are composed of lineages, which represent an evolving set of closely related haplotypes. The term haplotype describes the entire combination of substitutions retrieved from the complete sequence in any given sample and therefore indicates the tips of the phylogeny, whether a singleton or not. Numbers 1–16569 refer to the position of the substitution in the rCRS.27Andrews R.M. Kubacka I. Chinnery P.F. Lightowlers R.N. Turnbull D.M. Howell N. Reanalysis and revision of the Cambridge reference sequence for human mitochondrial DNA.Nat. Genet. 1999; 23: 147Crossref PubMed Scopus (2521) Google Scholar We followed the consensus nomenclature scheme31Richards M.B. Macaulay V.A. Bandelt H.J. Sykes B.C. Phylogeography of mitochondrial DNA in western Europe.Ann. Hum. Genet. 1998; 62: 241-260Crossref PubMed Google Scholar when possible. In many cases, we labeled previously unreported deep branches (e.g., L1c1c), understanding that these designations are meant to facilitate reading and future literature comparison and are prospective candidates of clades to be fully defined in the future, provided common ancestral substitution motifs could be identified in complete mtDNA sequences of other samples. Nomenclature within Hg L(xM,N) has been the subject of some ambiguity because of the relabeling of some of the clades. The clades L0d, L0f, L0k, and L5 were previously labeled L1d, L1f, L1k, and L1e, respectively. We followed the designation in5Torroni A. Achilli A. Macaulay V. Richards M. Bandelt H.J. Harvesting the fruit of the human mtDNA tree.Trends Genet. 2006; 22: 339-345Abstract Full Text Full Text PDF PubMed Scopus (351) Google Scholar, 8Kivisild T. Shen P. Wall D.P. Do B. Sung R. Davis K. Passarino G. Underhill P.A. Scharfe C. Torroni A. et al.The role of selection in the evolution of human mitochondrial genomes.Genetics. 2006; 172: 373-387Crossref PubMed Scopus (359) Google Scholar, 15Salas A. Richards M. De la Fe T. Lareu M.V. Sobrino B. Sanchez-Diz P. Macaulay V. Carracedo A. The making of the African mtDNA landscape.Am. J. Hum. Genet. 2002; 71: 1082-1111Abstract Full Text Full Text PDF PubMed Scopus (386) Google Scholar, 32Salas A. Richards M. Lareu M.V. Scozzari R. Coppa A. Torroni A. Macaulay V. Carracedo A. The African diaspora: Mitochondrial DNA and the Atlantic slave trade.Am. J. Hum. Genet. 2004; 74: 454-465Abstract Full Text Full Text PDF PubMed Scopus (202) Google Scholar for the definitions of the major branches with a single exception. We have eliminated the label L7 coined in5Torroni A. Achilli A. Macaulay V. Richards M. Bandelt H.J. Harvesting the fruit of the human mtDNA tree.Trends Genet. 2006; 22: 339-345Abstract Full Text Full Text PDF PubMed Scopus (351) Google Scholar and revert back to the original label L4a as suggested in13Kivisild T. Reidla M. Metspalu E. Rosa A. Brehm A. Pennarun E. Parik J. Geberhiwot T. Usanga E. Villems R. Ethiopian mitochondrial DNA heritage: Tracking gene flow across and around the gate of tears.Am. J. Hum. Genet. 2004; 75: 752-770Abstract Full Text Full Text PDF PubMed Scopus (200) Google Scholar because of the following: (1) A large number of samples (17) suggest position 16362 to be at the root of both clades, (2) both clades share similar distribution in East Africa and in southern West Eurasia, and (3) coalescence ages and the observed subclade-type architecture appear to be similar. We have not used the label L1c5 suggested by33Batini C. Coia V. Battaggia C. Rocha J. Pilkington M.M. Spedini G. Comas D. Destro-Bisol G. Calafell F. Phylogeography of the human mitochondrial L1c haplogroup: Genetic signatures of the prehistory of Central Africa.Mol. Phylogenet. Evol. 2007; 43: 635-644Crossref PubMed Scopus (51) Google Scholar because our complete mtDNA-based analysis indicates it to be L1c1a1, as suggested by.15Salas A. Richards M. De la Fe T. Lareu M.V. Sobrino B. Sanchez-Diz P. Macaulay V. Carracedo A. The making of the African mtDNA landscape.Am. J. Hum. Genet. 2002; 71: 1082-1111Abstract Full Text Full Text PDF PubMed Scopus (386) Google Scholar To avoid confusion, we have skipped this label and moved from L1c4 to L1c6. We added labeling for previously unlabeled bifurcations if they became relevant for our discussion.The term Khoisan is used in reference to two major ethnic groups of Southern Africa, the Khoi and San, though several other names exist for either one or both of these groups, such as the Khoi, Khoe, Khoi-San, and Khoe-San.African Hg L PhylogenyWe generated a maximum-parsimony tree of 624 complete mtDNA sequences belonging to Hg L(xM,N) (Figure S1). The tree was rooted according to8Kivisild T. Shen P. Wall D.P. Do B. Sung R. Davis K. Passarino G. Underhill P.A. Scharfe C. Torroni A. et al.The role of selection in the evolution of human mitochondrial genomes.Genetics. 2006; 172: 373-387Crossref PubMed Scopus (359) Google Scholar and includes 309 samples reported herein and 315 previously reported samples: 21 sequences from,23Ingman M. Kaessmann H. Paabo S. Gyllensten U. Mitochondrial genome variation and the origin of modern humans.Nature. 2000; 408: 708-713Crossref PubMed Scopus (1017) Google Scholar six from,10Maca-Meyer N. Gonzalez A.M. Larruga J.M. Flores C. Cabrera V.M. Major genomic mitochondrial lineages delineate early human expansions.BMC Genet. 2001; 2: 13Crossref PubMed Scopus (263) Google Scholar five from,34Torroni A. Rengo C. Guida V. Cruciani F. Sellitto D. Coppa A. Calderon F.L. Simionati B. Valle G. Richards M. et al.Do the four clades of the mtDNA haplogroup L2 evolve at different rates?.Am. J. Hum. Genet. 2001; 69: 1348-1356Abstract Full Text Full Text PDF PubMed Scopus (168) Google Scholar ten from,9Mishmar D. Ruiz-Pesini E. Golik P. Macaulay V. Clark A.G. Hosseini S. Brandon M. Easley K. Chen E. Brown M.D. et al.Natural selection shaped regional mtDNA variation in humans.Proc. Natl. Acad. Sci. USA. 2003; 100: 171-176Crossref PubMed Scopus (774) Google Scholar 93 from,24Howell N. Elson J.L. Turnbull D.M. Herrnstadt C. African laplogroup L mtDNA sequences show violations of clock-like evolution.Mol. Biol. Evol. 2004; 21: 1843-1854Crossref PubMed Scopus (29) Google Scholar 126 from,8Kivisild T. Shen P. Wall D.P. Do B. Sung R. Davis K. Passarino G. Underhill P.A. Scharfe C. Torroni A. et al.The role of selection in the evolution of human mitochondrial genomes.Genetics. 2006; 172: 373-387Crossref PubMed Scopus (359) Google Scholar 23 from,5Torroni A. Achilli A. Macaulay V. Richards M. Bandelt H.J. Harvesting the fruit of the human mtDNA tree.Trends Genet. 2006; 22: 339-345Abstract Full Text Full Text PDF PubMed Scopus (351) Google Scholar four from,25Behar D.M. Metspalu A. Kivisild T. Rosset S. Tzur S. Hadid Y. Yodkovsky G. Rosengarten D. Pereira L. Amorim A. et al.Counting the founders: The matrilineal genetic ancestry of the Jewish Diaspora.PLoS ONE. 2008; (in press)Google Scholar and 27 from.16Quintana-Murci L. Quach H. Harmant C. Luca F. Massonnet B. Patin E. Sica L. Mouguiama-Daouda P. Comas D. Tzur S. et al.Maternal traces of deep common ancestry and asymmetric gene flow between Pygmy hunter-gatherers and Bantu-speaking farmers.Proc. Natl. Acad. Sci. USA. 2008; 105: 1596-1601Crossref PubMed Scopus (138) Google Scholar The genotyping information from5Torroni A. Achilli A. Macaulay V. Richards M. Bandelt H.J. Harvesting the fruit of the human mtDNA tree.Trends Genet. 2006; 22: 339-345Abstract Full Text Full Text PDF PubMed Scopus (351) Google Scholar, 34Torroni A. Rengo C. Guida V. Cruciani F. Sellitto D. Coppa A. Calderon F.L. Simionati B. Valle G. Richards M. et al.Do the four clades of the mtDNA haplogroup L2 evolve at different rates?.Am. J. Hum. Genet. 2001; 69: 1348-1356Abstract Full Text Full Text PDF PubMed Scopus (168) Google Scholar included herein corrects several inaccuracies that were identified during the establishment of the phylogeny. Sequence data from35Gonder M.K. Mortensen H.M. Reed F.A. de Sousa A. Tishkoff S.A. Whole-mtDNA geno