Fig. 4.
The decay of heterozygosity plotted against geographic distance between populations and a possible origin of expansion. (A) Heterozygosity in the HGDP-CEPH populations against distance from Addis Ababa, Ethiopia (9N, 38E). Distances were corrected for large bodies of water. The equation of the regression line is heterozygosity = 0.7682 - (6.52 × 10-6) × (distance from Addis Ababa). R2 = 0.7630. (B) Simulation results of the decay of heterozygosity with distance using a model of a serial founder effect. The simulation is based exclusively on mutation at a realistic rate and drift, as described in more detail in Supporting Text. The parameter values generating the simulation were chosen so as to fit the observed ΔH of A. The number of bottlenecks is n = 100, and the number of founders per bottleneck, Nb, is 250, which approximates the effective population size of a population of hunter-gatherers (35, 36). Other pairs of values of n and Nb in the same ratio would fit the data equally well, because their ratio is the main quantity affecting the slope. The equation of the fitted line is heterozygosity = 0.8761 - 0.0012 × (distance from the parental colony). R2 = 0.8587.