Variation of female and male lineages in sub-Saharan populations: the importance of sociocultural factors.
In this paper, we present a study of genetic variation in sub-Saharan Africa, which is based on published and unpublished data on fast-evolving (hypervariable region 1 of mitochondrial DNA and six microsatellites of Y chromosome) and slow-evolving (haplogroup frequencies)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 Nupsilon is substantially higher in food producers than in hunter-gatherers as determined by fast-evolving polymorphisms (1.76 versus 0.11). This finding indicates that the two population groups differ substantially in female and male migration rate and/or effective size. The difference also persists when linguistically homogeneous populations are used and outlier populations are eliminated (1.78 vs 0.19) or when the jacknife procedure is applied to a paired population data set (1.32 to 7.84 versus 0.14 to 0.66). The higher ratio of mtDNA to Y-chromosome Nnu in food producers than in hunter-gatherers is further confirmed by the use of slow-evolving polymorphisms (1.59 to 7.91 versus 0.12 to 0.35). To explain these results, we propose a model that 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 that is revealed through the analysis of mitochondrial and Y-chromosomal intrapopulational variation.
Destro-Bisol
Giovanni
G
Department of Animal and Human Biology, University "La Sapienza," Rome, Italy. destrobisol@uniroma1.it
Donati
Francesco
F
Coia
Valentina
V
Boschi
Ilaria
I
Verginelli
Fabio
F
Caglià
Alessandra
A
Tofanelli
Sergio
S
Spedini
Gabriella
G
Capelli
Cristian
C
D017954:Africa South of the Sahara; D041322:Chromosomes, Human, Y / Q000235:genetics*; D003466:Cultural Characteristics; D004272:DNA, Mitochondrial / Q000235:genetics*; D005006:Ethnicity / Q000235:genetics; D019143:Evolution, Molecular; D005260:Female; D014644:Genetic Variation; D005828:Genetics, Population; D006239:Haplotypes; D006801:Humans; D008297:Male; D018895:Microsatellite Repeats; D008957:Models, Genetic; D012931:Social Environment
D004272:DNA, Mitochondrial