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Female and Male Lineages in Sub-Saharan Populations:

Molecular Biology and Evolution
Variation of Female and Male Lineages in Sub-Saharan Populations: The Importance of Socio-Cultural Factors
Giovanni Destro-Bisol et al.
Abstract
In this paper, we present a study regarding genetic variation in sub-Saharan Africa, which is based on published and unpublished data concerning fast-evolving (hypervariable region 1 of mitochondrial DNA and six microsatellites of Y-chromosome) and slow-evolving (haplogroup frequencies) polymorphisms of mtDNA and Y-chromosome. Our study reveals a striking difference in the genetic structure of food-producer (Bantu and Sudanic speakers) and hunter-gatherer populations (Pygmies, !Kung and Hadza). In fact, the ratio of mtDNA to Y-chromosome N is substantially higher in food-producers than in hunter-gatherers using fast evolving polymorphisms (1.76 vs 0.11). This indicates that the two population groups differ substantially in female and male migration rate and/or effective size. The difference also persists when using linguistically homogeneous populations and eliminating outlier populations (1.78 vs 0.19) or applying the jacknife procedure to a paired population dataset (1.32-7.84 vs 0.14-0.66). The higher ratio of mtDNA to Y-chromosome N in food-producers than in hunter-gatherers is further confirmed by the use of slow evolving polymorphisms (1.59-7.91 vs 0.12-0.35). To explain these results, we propose a model which integrates demographic and genetic aspects and incorporates ethnographic knowledge. In such a model the asymmetric gene flow, polyginy and patrilocality play an important role in differentiating the genetic structure of sub-Saharan populations. The existence of an asymmetric gene flow is supported by the phylogeographic features of mtDNA and Y-chromosome haplogroups found in the two population groups. The role of polyginy and patrilocality is sustained by the evidence of a differential pressure of genetic drift and gene flow on maternal and paternal lineages of food-producers and hunter-gatherers which is revealed through the analysis of mitochondrial and Y-chromosomal intra-populational variation.

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