Human genetic variation and the dispersal of Bantu-speaking populations

The expansion of Bantu-speaking agropastoralist populations had a significant impact on the genetic, linguistic, and cultural variation of sub-Saharan Africa. Bantu languages originated in an area close to the present-day border between Cameroon and Nigeria not earlier than 5000 years ago. From their homeland, these languages spread south and east through most of sub-Saharan Africa becoming by far the largest African linguistic family. Even though it is generally accepted that this dispersal was the result of the migration of people, there are still many unanswered questions about the dynamics of this process. The demic consequences of this dispersal are reflected in the relatively high genetic homogeneity observed across most of sub-Saharan Africa populations but its implications on the genetic diversity of the continent are not fully appreciated yet. Incorporating African populations’ genome-wide data available from Prof. Capelli’s research group with previously published data, this thesis addresses and tries to answer some of the questions related to the genetic impact of this dispersal. I start by addressing the process of admixture between the migrating Bantu speakers and previous inhabitants in south-east Africa. Rejecting the hypothesis of a potentially pre-Bantu component found in south-east African Bantu-speaking populations as the result of extensive gene flow, I highlight the importance of the demographic dynamics associated with the Bantu dispersal in shaping the genetic diversity of these communities. I then focus on the analysis of the genetic variation observed in sub-Saharan Niger-Congo populations, highlighting the impact of admixture events and the existence of population structure within Bantu speakers, often considered as a genetically homogeneous group. Lastly, I attempt to mask the admixture events I found and reconcile genetics, geography, and linguistics in order to reconstruct the relationships among the Bantu-speaking populations across the continent. Overall, my results emphasize the diversity observed in Bantu-speaking populations and the impact their rapid dispersal and contact with other communities had on the genetic variation they show.