Migration of Chadic speaking pastoralists within Africa based on population structure of Chad Basin and phylogeography of mitochondrial L3f haplogroup.
Migration of Chadic speaking pastoralists within Africa based on population structure of Chad Basin and phylogeography of mitochondrial L3f haplogroup.
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DOI：
10.1186/1471-2148-9-63
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发表时间：
2009-03-23
影响因子：
3.4
通讯作者：
Pereira L
中科院分区：
文献类型：
--
作者：
Cerný V;Fernandes V;Costa MD;Hájek M;Mulligan CJ;Pereira L
乍得盆地位于非洲萨赫勒地区的双向走廊内，是当今撒哈拉以南非洲人口最多的地区之一。其定居点的起源似乎与距今约10，000年（YBP）开始的全新世气候改善（水生资源）有关。虽然尼罗-撒哈拉语系和刚果-刚果语系在这里都有，但最多样化的是属于亚非语系的乍得语分支。在这篇文章中，我们研究了提出的古代迁移的乍得牧民从东非的语言数据和测试的遗传痕迹，这种迁移在现存的乍得语人口。我们对16个L3 f单倍型进行了全线粒体基因组测序，重点是几乎只发生在乍得盆地讲乍得语的人中的进化枝L3 f3。这些数据支持了L3 f系统发育树的重建和所有内部分支到最近共同祖先的时间的计算。估计L3 f3单倍群的年代约为8，000 YBP，这与讲乍得语的牧民的迁移以及他们与东非其他亚非群体的语言差异非常一致。总体而言，亚非语系呈现出较低的群体结构，92.4%的mtDNA变异存在于群体内，只有3.4%的变异可以归因于语言分支之间的多样性。讲乍得语的人口形成了一个相对同质的群体，比其他亚非分支（柏柏尔人、闪米特人和库希特人）表现出较低的多样化。我们的研究结果支持东非起源的线粒体L3 f3进化枝，目前几乎完全在乍得讲乍得盆地的人生活。基于全基因组序列的年代测定显示，祖先单倍群L3 f一定是在非洲外迁移后不久（约57，100 ± 9，400 YBP）出现的，但“Chadic”L3 f3分支的内部变异要少得多，这表明在全新世时期约8，000 ± 2，500 YBP的扩张。考古、语言和气候数据表明，乍得盆地的这一时期特别有利于来自非洲东北部的牧民的扩张。
Chad Basin, lying within the bidirectional corridor of African Sahel, is one of the most populated places in Sub-Saharan Africa today. The origin of its settlement appears connected with Holocene climatic ameliorations (aquatic resources) that started ~10,000 years before present (YBP). Although both Nilo-Saharan and Niger-Congo language families are encountered here, the most diversified group is the Chadic branch belonging to the Afro-Asiatic language phylum. In this article, we investigate the proposed ancient migration of Chadic pastoralists from Eastern Africa based on linguistic data and test for genetic traces of this migration in extant Chadic speaking populations. We performed whole mitochondrial genome sequencing of 16 L3f haplotypes, focused on clade L3f3 that occurs almost exclusively in Chadic speaking people living in the Chad Basin. These data supported the reconstruction of a L3f phylogenetic tree and calculation of times to the most recent common ancestor for all internal clades. A date ~8,000 YBP was estimated for the L3f3 sub-haplogroup, which is in good agreement with the supposed migration of Chadic speaking pastoralists and their linguistic differentiation from other Afro-Asiatic groups of East Africa. As a whole, the Afro-Asiatic language family presents low population structure, as 92.4% of mtDNA variation is found within populations and only 3.4% of variation can be attributed to diversity among language branches. The Chadic speaking populations form a relatively homogenous cluster, exhibiting lower diversification than the other Afro-Asiatic branches (Berber, Semitic and Cushitic). The results of our study support an East African origin of mitochondrial L3f3 clade that is present almost exclusively within Chadic speaking people living in Chad Basin. Whole genome sequence-based dates show that the ancestral haplogroup L3f must have emerged soon after the Out-of-Africa migration (around 57,100 ± 9,400 YBP), but the "Chadic" L3f3 clade has much less internal variation, suggesting an expansion during the Holocene period about 8,000 ± 2,500 YBP. This time period in the Chad Basin is known to have been particularly favourable for the expansion of pastoralists coming from northeastern Africa, as suggested by archaeological, linguistic and climatic data.
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