George Busby | Search bioRxiv

bioRxiv2016

Complex ancient genetic structure and cultural transitions in southern African populations.

The characterization of the structure of southern Africa populations has been the subject of numerous genetic, medical, linguistic, archaeological and anthropological investigations. Current diversity in the subcontinent is the result of complex episodes of genetic admixture and cultural contact between the early inhabitants and the migrants that have arrived in the region over the last 2,000 years. Here we analyze 1,856 individuals from 91 populations, comprising novel and available genotype data to characterize the genetic ancestry profiles of 631 individuals from 51 southern African populations. Combining local ancestry and allele frequency analyses we identify a tripartite, ancient, Khoesan-related genetic structure, which correlates with geography, but not with linguistic affiliation or subsistence strategy. The fine mapping of these components in southern African populations reveals admixture dynamics and episodes of cultural reversion involving several Khoesan groups and highlights different mixtures of ancestral components in Bantu speakers and Coloured individuals.

Genomics↗

bioRxiv2016

Admixture into and within sub-Saharan Africa

Understanding patterns of genetic diversity is a crucial component of medical research in Africa. Here we use haplotype-based population genetics inference to describe gene-flow and admixture in a collection of 48 African groups with a focus on the major populations of the sub-Sahara. Our analysis presents a framework for interpreting haplotype diversity within and between population groups and provides a demographic foundation for genetic epidemiology in Africa. We show that coastal African populations have experienced an influx of Eurasian haplotypes as a series of admixture events over the last 7,000 years, and that Niger-Congo speaking groups from East and Southern Africa share ancestry with Central West Africans as a result of recent population expansions associated with the adoption of new agricultural technologies. We demonstrate that most sub-Saharan populations share ancestry with groups from outside of their current geographic region as a result of large-scale population movements over the last 4,000 years. Our in-depth analysis of admixture provides an insight into haplotype sharing across different geographic groups and the recent movement of alleles into new climatic and pathogenic environments, both of which will aid the interpretation of genetic studies of disease in sub-Saharan Africa.

Genomics↗