The expansion of modern humans out of Africa within the past 100 Kya sampled only a subset of the variation in the African gene pool. As humans migrated farther from Africa and then expanded locally to occupy all of Eurasia, even more drift accumulated because the subsets of the local gene pools carried forward by migrants became successively more homogeneous. The result is a general clinal pattern of decreasing heterozygosity and increasing linkage disequilibrium with increasing distance from Africa, but with a marked founder effect associated with the expansion out of Africa. Not shown are the ever-present small-scale migrations among groups or the recent migrations between regions.