Genomic studies in African populations provide unique opportunities to understand
disease aetiology, human diversity and population history. In the largest study of its
kind, comprising genome-wide data from 6,400 individuals, and whole-genome
sequences from 1,978 individuals from rural Uganda, we find evidence of
geographically-correlated fine-scale population substructure. Historically, the ancestry
of modern Ugandans is best represented by a mixture of ancient East African
pastoralists. We demonstrate the value of the largest sequence panel from Africa to
date as an imputation resource. Examining 34 cardiometabolic traits, we show
systematic differences in trait heritability between European and African populations,
probably reflecting the differential impact of genes and environment. In a multi-trait
pan-African GWAS of up to 14,126 individuals, we identify novel loci associated with
anthropometric, haematological, lipid and glycemic traits. We find that several
functionally important signals are driven by Africa-specific variants, highlighting the
value of studying diverse populations across the region.