Wednesday, January 03, 2007

East African mtDNA

their main selling points: whole mtDNA genome sequencing, and more East African population samples...their conclusion: they confirm the role of East African populations (especially around Tanzania?) in the origin and spread of humans to the rest of Africa and the world.

Whole mtDNA Genome Sequence Analysis of Ancient African Lineages

Mary Katherine Gonder, Holly M. Mortensen, Floyd A. Reed, Alexandra de Sousa and Sarah A. Tishkoff

Molecular Biology and Evolution Accepted for publication December 12, 2006.

Abstract: Studies of human mtDNA genomes demonstrate that the root of the human phylogenetic tree occurs in Africa. Although two mtDNA lineages with an African origin (haplogroups M and N) were the progenitors of all non-African haplogroups, macrohaplogroup L (including haplogroups L0-L6) is limited to sub-Saharan Africa. Several L haplogroup lineages occur most frequently in eastern Africa (e.g., L0a, L0f, L5, L3g), but some are specific to certain ethnic groups, such as haplogroup lineages L0d and L0k that previously have been found nearly exclusively among southern African "click" speakers. Few studies have included multiple mtDNA genome samples belonging to haplogroups that occur in eastern and southern Africa but are rare or absent elsewhere. This lack of sampling in eastern Africa makes it difficult to infer relationships among mtDNA haplogroups or to examine events that occurred early in human history. We sequenced 62 complete mtDNA genomes of ethnically diverse Tanzanians, southern African Khoisan speakers and Bakola Pygmies and compared them to a global pool of 226 mtDNA genomes. From these, we infer phylogenetic relationships amongst mtDNA haplogroups and estimate the time to most recent common ancestor (TMRCA) for haplogroup lineages. These data suggest that Tanzanians have high genetic diversity and possess ancient mtDNA haplogroups, some of which are either rare (L0d and L5) or absent (L0f) in other regions of Africa. We propose that a large and diverse human population(s) has persisted in eastern Africa and that eastern Africa may have been an ancient source of dispersion of modern humans both within and outside of Africa.

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