The expansion of mtDNA haplogroup L3 within and out of Africa

Although fossil remains show that anatomically modern humans dispersed out of Africa into the Near East ∼100 to 130 ka, genetic evidence from extant populations has suggested that non-Africans descend primarily from a single successful later migration. Within the human mitochondrial DNA (mtDNA) tree, haplogroup L3 encompasses not only many sub-Saharan Africans but also all ancient non-African lineages, and its age therefore provides an upper bound for the dispersal out of Africa. An analysis of 369 complete African L3 sequences places this maximum at ∼70 ka, virtually ruling out a successful exit before 74 ka, the date of the Toba volcanic supereruption in Sumatra. The similarity of the age of L3 to its two non-African daughter haplogroups, M and N, suggests that the same process was likely responsible for both the L3 expansion in Eastern Africa and the dispersal of a small group of modern humans out of Africa to settle the rest of the world. The timing of the expansion of L3 suggests a link to improved climatic conditions after ∼70 ka in Eastern and Central Africa rather than to symbolically mediated behavior, which evidently arose considerably earlier. The L3 mtDNA pool within Africa suggests a migration from Eastern Africa to Central Africa ∼60 to 35 ka and major migrations in the immediate postglacial again linked to climate. The largest population size increase seen in the L3 data is 3-4 ka in Central Africa, corresponding to Bantu expansions, leading diverse L3 lineages to spread into Eastern and Southern Africa in the last 3-2 ka.FCT, the Portuguese Foundation for Science and Technology, supported this work through the research project PTDC/ANT/66275/2006 and the personal grants to V.F. (SFRH/BD/61342/2009), J.B.P. (SFRH/BD/45657/2008), M.D.C. (SFRH/BD/48372/2008), N.M.S. (SFRH/BD/69119/2010), and P.S. (SFRH/BPD/64233/2009). P.S. also thanks the de Laszlo Foundation for financial support. The Ministry of Education of the Czech Republic also supported this work through the grant KONTAKT ME 917. IPATIMUP is an Associate Laboratory of the Portuguese Ministry of Science, Technology, and Higher Education and is partially supported by FCT