透过线粒体全基因组看非洲俾格米人的部落历史

熊荣川 译

摘要

俾格米人是目前少数几个生活在亚撒哈拉非洲地区的狩猎聚居部落之一。根据他们现在的地理分布，主要可以分为东、西两大部落。它们散布在中非腹地，周围是和他们有着复杂的社会、经济联系的班图语农耕部落。为了探究俾格米人的部落种群历史，使用了一种种群分析方法对来自10个中非部落的总计205个线粒体全基因组进行了分析。结果两个俾格米部落之间并未观察到重叠的母系支系，西部部落作为一个共享单倍型L1c，而绝大部分东部俾格米支系分布在亚支系（地位次于单倍型）L0a、L2a及L5。基于贝叶斯综合模拟的种群发育分析推断俾格米人两个部落及图班语农耕部落的母系祖先早在70000年前就发生分化。有证据表明班图语农耕部族的祖先从65000年前开始种群数量有所扩张，时间上早于班图语的扩散。然后，俾格米祖先的有效种群大小在接下来的27000年内保持稳定，和Last Glacial Maximum的证据一致。东西俾格米部落之后发生分化，有证据表明分化后只有西部部落和班图语农耕部落发生了迁徙。西部俾格米部落有在4000-650年前发生瓶颈效应的迹象，伴随着班图语的扩散，而东部俾格米部落则经历了一次更早的种群数量减少事件（20000-4000年前）。综上所述，作为首次在部落种群水平上分析亚撒哈拉非洲地区的线粒体全基因组序列的探索，结果不仅支持了之前的发现而且也对俾格米部落的人口学史提出了新的视野，为研究非洲大陆的古代人口分布研究提供了基础。

关键词：线粒体基因组，非洲俾格米人 联合模拟 人口统计学 系统发育地理学 

原文

Insights into the Demographic History of African Pygmies from Complete Mitochondrial Genomes

Abstract

Pygmy populations are among the few hunter-gatherers currently living in sub-Saharan Africa and are mainly represented by two groups, Eastern and Western, according to their current geographical distribution. They are scattered across the Central African belt and surrounded by Bantu-speaking farmers, with whom they have complex social and economic interactions. To investigate the demographic history of Pygmy groups, a population approach was applied to the analysis of 205 complete mitochondrial DNA (mtDNA) sequences from ten central African populations. No sharing of maternal lineages was observed between the two Pygmy groups, with haplogroup L1c being characteristic of the Western group but most of Eastern Pygmy lineages falling into subclades of L0a, L2a, and L5. Demographic inferences based on Bayesian coalescent simulations point to an early split among the maternal ancestors of Pygmies and those of Bantu-speaking farmers (;70,000 years ago [ya]). Evidence for population growth in the ancestors of Bantu-speaking farmers has been observed, starting ;65,000 ya, well before the diffusion of Bantu languages. Subsequently, the effective population size of the ancestors of Pygmies remained constant over time and~27,000ya, coincident with the Last Glacial Maximum, Eastern and Western Pygmies diverged, with evidence of subsequent migration only among the Western group and the Bantu-speaking farmers. Western Pygmies show signs of a recent bottleneck 4,000–650 ya, coincident with the diffusion of Bantu languages, whereas Eastern Pygmies seem to have experienced a more ancient decrease in population size (20,000–4,000ya). In conclusion, the results of this first attempt at analyzing complete mtDNA sequences at the population level in sub-Saharan Africa not only support previous findings but also offer new insights into the demographic history of Pygmy populations, shedding new light on the ancient peopling of the African continent.

Key words: mitochondrial genome, African Pygmies, coalescent simulations, demography, phylogeography

参考文献