Gonder Mary Katherine, Mortensen Holly M, Reed Floyd A, de Sousa Alexandra, Tishkoff Sarah A
Department of Biology, University of Maryland, MD, USA.
Mol Biol Evol. 2007 Mar;24(3):757-68. doi: 10.1093/molbev/msl209. Epub 2006 Dec 28.
Studies of human mitochondrial (mt) DNA genomes demonstrate that the root of the human phylogenetic tree occurs in Africa. Although 2 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, and 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 with 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 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.
对人类线粒体（mt）DNA基因组的研究表明，人类系统发育树的根源在非洲。尽管两个起源于非洲的mtDNA谱系（单倍群M和N）是所有非非洲单倍群的祖先，但大的单倍群L（包括单倍群L0-L6）仅限于撒哈拉以南非洲地区。几个L单倍群谱系在东非最为常见（例如L0a、L0f、L5和L3g），但有些则特定于某些族群，如单倍群谱系L0d和L0k，此前几乎只在南非“咔嗒”语使用者中发现。很少有研究纳入属于在东非和南非出现但在其他地方罕见或不存在的单倍群的多个mtDNA基因组样本。东非缺乏这样的样本使得难以推断mtDNA单倍群之间的关系，也难以研究人类历史早期发生的事件。我们对来自不同种族的坦桑尼亚人、南非科伊桑语使用者和巴科拉俾格米人的62个完整mtDNA基因组进行了测序，并将它们与226个mtDNA基因组的全球样本库进行了比较。由此，我们推断了mtDNA单倍群之间的系统发育关系，并估计了单倍群谱系的最近共同祖先时间（TMRCA）。这些数据表明，坦桑尼亚人具有高度的遗传多样性，拥有古老的mtDNA单倍群，其中一些在非洲其他地区要么罕见（L0d和L5）要么不存在（L0f）。我们提出，东非一直存在着一个庞大且多样化的人类群体，并且东非可能一直是现代人类在非洲内外扩散的古老源头。
