Fig. 2.
Haplotype-based estimates of genetic sharing between Europe and Africa show a significant latitudinal gradient where the highest sharing is in the Iberian Peninsula. Genetic sharing between geographic regions is represented as a density map of WEA estimates for 30 European populations where haplotypes are IBD with (A) Sub-Saharan Africa, (B) North Africa and (C) the Near East. The Canary Islands are shown in the Lower Left. (D) To determine the relationship between latitude and mean IBD count (WEA) within Europe, we regressed WEA on log(sin(latitude)). The sine of the latitude was used to obtain distance-appropriate vertical values; then we log-transformed these value to obtain the expected decay of allele sharing in 2-dimensional habitats (52). The P value of the regression for IBD shared between North Africa and Europe is 7.4 × 10−8.