Figure 1.—

The probability of misclassifying an African allele detected in a European population as Europe specific (and thus of outside-African origin). We considered only those African alleles that were not detected in at least one African population. The probability was calculated as

where r is the number of sites analyzed, n_i is the number of African populations lacking allele i, m is the total number of populations, and k is the number of populations considered. Note that this equation assumes independence among sites and does not account for sampling heterogeneity. Low variability fragments (▪) comprise six fragments that show very little (one segregating singleton at most) or no variation in Europe. Normal variability fragments (□) comprise six fragments that are not markedly reduced in variability in the European population.