Cerný V, Hájek M, Cmejla R, Brůzek J, Brdicka R
Department of Anthropology & Environment, Institute of Archaeology, Czech Academy of Sciences, Czech Republic.
Ann Hum Biol. 2004 Sep-Oct;31(5):554-69. doi: 10.1080/03014460412331287182.
No mitochondrial DNA (mtDNA) sequences from Chadic-speaking peoples have yet been reported, even though these populations inhabit a vast territory from eastern Nigeria to central Chad. This paper deals with the mtDNA sequences of four Central Chadic populations (Hide, Kotoko, Mafa and Masa) from northern Cameroon, biological samples from which were collected during anthropological research in the area of their homeland.
The main goals of this article are to report new mtDNA sequences of Chadic-speaking populations, to analyse their genetic diversity and to establish their relationships within the peri-Saharan area in respect of geography and languages.
The analyses are based on 104 mtDNA haplotypes, which can be localized into four different areas of northern Cameroon. Data collection was based on a strict geographical sampling strategy; the ethnonyms are retained here only for comparative purposes.
None of the examined Chadic populations displays a departure from the normal mismatch distribution pattern, and the null hypothesis of the expansion event cannot be rejected. Analyses of molecular variance and F(ST) genetic distances revealed that the Chadic-speaking groups of northern Cameroon share more similarities with the populations of the Upper and Middle Nile Valley and East Africa than with populations from Central Africa. The results show geographical clustering to be more important than the correlation of linguistic affiliations with molecular genetic data.
The observation that the Chadic group reveals some affinities to East Africans is extremely surprising giving the present-day geographical distance (around 2000 km) between them. These observations complement recent linguistic and archaeological findings, which consider the Chadic branch in the Afro-Asiatic phylum to be of eastern origin. A continuous, well-defined, geographic sampling strategy of the different genetic polymorphisms of the native populations of sub-Saharan Africa is further needed as the only way of understanding the differentiation of the mtDNA sequences at a micro-regional scale.
尽管乍得语族人群居住在从尼日利亚东部到乍得中部的广阔区域，但尚未有该语族人群线粒体DNA（mtDNA）序列的报道。本文研究了来自喀麦隆北部的四个中乍得语族人群（希德、科托科、马法和马萨）的mtDNA序列，这些生物样本是在其家乡地区的人类学研究中收集的。
本文的主要目标是报告乍得语族人群新的mtDNA序列，分析其遗传多样性，并根据地理和语言情况确定他们在撒哈拉周边地区的关系。
分析基于104个mtDNA单倍型，这些单倍型可定位到喀麦隆北部的四个不同区域。数据收集基于严格的地理采样策略；这里保留族名仅用于比较目的。
在所研究的乍得语族人群中，没有一个偏离正常的错配分布模式，扩张事件的零假设不能被拒绝。分子方差分析和F(ST)遗传距离显示，喀麦隆北部讲乍得语的群体与尼罗河上游和中游流域以及东非的人群比与中非的人群有更多相似之处。结果表明，地理聚类比语言归属与分子遗传数据的相关性更重要。
考虑到乍得语族群体与东非人群目前约2000公里的地理距离，观察到乍得语族群体与东非人群有一些亲缘关系是极其令人惊讶的。这些观察结果补充了最近的语言和考古发现，这些发现认为亚非语系中的乍得语族起源于东部。作为在微观区域尺度上理解mtDNA序列分化的唯一方法，进一步需要对撒哈拉以南非洲本地人群的不同基因多态性采用连续、明确的地理采样策略。
