APOL1 and chronic kidney disease: We observe examples where certain population-specific variants significantly associated with complex traits: examples include the African specific Duffy null variant rs2814778 alone accounts for 15–20% of variability in white blood cell counts among AAs [4,46], and the trypanolytic APOL1 G1/G2 alleles conferring an estimated ~20% lifetime risk of developing chronic kidney disease [47,48].