Rosa Alexandra, Ornelas Carolina, Jobling Mark A, Brehm António, Villems Richard
Department of Evolutionary Biology, Estonian Biocentre, Riia 23, Tartu, Estonia.
BMC Evol Biol. 2007 Jul 27;7:124. doi: 10.1186/1471-2148-7-124.
The geographic and ethnolinguistic differentiation of many African Y-chromosomal lineages provides an opportunity to evaluate human migration episodes and admixture processes, in a pan-continental context. The analysis of the paternal genetic structure of Equatorial West Africans carried out to date leaves their origins and relationships unclear, and raises questions about the existence of major demographic phenomena analogous to the large-scale Bantu expansions. To address this, we have analysed the variation of 31 binary and 11 microsatellite markers on the non-recombining portion of the Y chromosome in Guinea-Bissau samples of diverse ethnic affiliations, some not studied before.
The Guinea-Bissau Y chromosome pool is characterized by low haplogroup diversity (D = 0.470, sd 0.033), with the predominant haplogroup E3a*-M2 shared among the ethnic clusters and reaching a maximum of 82.2% in the Mandenka people. The Felupe-Djola and Papel groups exhibit the highest diversity of lineages and harbor the deep-rooting haplogroups A-M91, E2-M75 and E3*-PN2, typical of Sahel's more central and eastern areas. Their genetic distinction from other groups is statistically significant (P = 0.01) though not attributable to linguistic, geographic or religious criteria. Non sub-Saharan influences were associated with the presence of haplogroup R1b-P25 and particular lineages of E3b1-M78.
The predominance and high diversity of haplogroup E3a*-M2 suggests a demographic expansion in the equatorial western fringe, possibly supported by a local agricultural center. The paternal pool of the Mandenka and Balanta displays evidence of a particularly marked population growth among the Guineans, possibly reflecting the demographic effects of the agriculturalist lifestyle and their putative relationship to the people that introduced early cultivation practices into West Africa. The paternal background of the Felupe-Djola and Papel ethnic groups suggests a better conserved ancestral pool deriving from East Africa, from where they have supposedly migrated in recent times. Despite the overall homogeneity in a multiethnic sample, which contrasts with their social structure, minor clusters suggest the imprints of multiple peoples at different timescales: traces of ancestral inhabitants in haplogroups A-M91 and B-M60, today typical of hunter-gatherers; North African influence in E3b1-M78 Y chromosomes, probably due to trans-Saharan contacts; and R1b-P25 lineages reflecting European admixture via the North Atlantic slave trade.
许多非洲Y染色体谱系的地理和民族语言分化为在泛大陆背景下评估人类迁徙事件和混合过程提供了契机。迄今为止，对赤道西非父系遗传结构的分析仍未明确其起源和关系，并引发了关于是否存在类似于大规模班图扩张的主要人口现象的疑问。为解决这一问题，我们分析了几内亚比绍不同族裔样本（其中一些此前未被研究过）Y染色体非重组部分的31个二元标记和11个微卫星标记的变异情况。
几内亚比绍的Y染色体库的特点是单倍群多样性较低（D = 0.470，标准差0.033），主要单倍群E3a*-M2在各民族群体中均有分布，在曼丁卡人群中占比最高，达82.2%。费卢佩-乔拉和帕佩尔群体表现出最高的谱系多样性，并且拥有扎根较深的单倍群A-M91、E2-M75和E3*-PN2，这些单倍群在萨赫勒地区更中部和东部地区较为典型。它们与其他群体的遗传差异具有统计学意义（P = 0.01），但并非由语言、地理或宗教标准导致。非撒哈拉以南地区的影响与单倍群R1b-P25以及E3b1-M78的特定谱系的存在有关。
单倍群E3a*-M2的优势和高度多样性表明赤道西部边缘地区存在人口扩张，可能受到当地农业中心的支持。曼丁卡和巴兰塔的父系群体显示出几内亚人中有特别显著的人口增长迹象，这可能反映了农耕生活方式的人口统计学影响以及他们与将早期耕种方式引入西非的人群的假定关系。费卢佩-乔拉和帕佩尔族裔群体的父系背景表明其源自东非的祖先群体保存得更好，推测他们是近期从那里迁移而来。尽管在多民族样本中总体具有同质性（这与其社会结构形成对比），但小群体表明在不同时间尺度上有多个群体留下的印记：单倍群A-M91和B-M60中存在祖先居民的痕迹，如今这些单倍群在狩猎采集者中较为典型；E3b1-M78 Y染色体中有北非影响，可能是由于跨撒哈拉接触；R1b-P25谱系反映了通过北大西洋奴隶贸易的欧洲混合血统。
