The slave-trade and beyond: the genetics of recent African migrations

Human genetic variation commonly exhibits geographic structuring as a consequence of demographic history (such as population subdivision, migration, and admixture or replacement), as well as locus-specific forces such as selection, mutation and recombination. Thus, dissecting the patterns of this variation is important for the reconstruction of human evolutionary history, and can contribute to the understanding of the genetic basis of phenotypic adaptation and complex disease.

Drawn by the knowledge of high levels of genetic diversity and low levels of linkage disequilibrium (which have important implications for the mapping of disease susceptibility loci), geneticists are increasingly turning their attention to Africa, the continent of origin of our species. The African Genome Variation Project has enhanced our understanding of the genetic variation in West, West-central and East Africa, and started to reveal the influence of pre-historical and historical large-scale migrations and expansions on the distribution of the genetic diversity across the continent.

Here, we propose to complement these studies with a detailed genomic study of our own collection of samples, and to provide a detailed characterization of the timing and extent of important recent migrations that occurred within Africa and from Africa to the Americas. Firstly, the student will combine public African datasets with our samples from Southwest and Southeast Africa to model the significant demographic shift in Sub-Saharan Africa that took place during the Bantu expansion. Secondly, they will combine this extended contemporary African dataset with ancient DNA (aDNA) analyses of human remains recovered from slave cemeteries located in the main receiving ports in Northeast and Southeast Brazil, and modern DNA analyses of descendants of enslaved Africans (Brazilians) collected in the same regions, to investigate the ethnic origins, demographic history and contemporary legacies of the trans-Atlantic slave trade. Given the historical evidence on different forced migratory routes from Africa to the Northeastern and Southeastern Brazilian ports, the shift in the relative importance of these routes through time, and the large number of slaves carried (ten times more than were carried to North America), the study of the African diaspora in Brazil provides a unique opportunity to understand the population dynamics of the trans-Atlantic slave trade. The student will apply both analytical and simulation-based methods to test different evolutionary scenarios, and to infer the main population parameters (such as population sizes, divergence times, migration rates, and timing and magnitude of recent admixture events) that gave rise to the contemporary diversity of European and European-derived populations. By using such a complete dataset and state-of-the-art techniques, the project will be able to shed light on the demographic history of Africa and of populations influenced by African migrations, and on the fundamental processes of human migration.

Finally, pairing this genomic data with ecological, historical, linguistic and other socio-economical variables, as well as with morphological and biomedical trait values such as skin colour, body mass index and blood pressure, the student will be able to interpret a range of genetic and non-genetic dimensions of African variation, including disease susceptibility, morphologic variation, linguistic differentiation, and cultural and social practices.

Applications should be made via the link: http://www2.le.ac.uk/departments/genetics/postgraduate/phd-studentships