D Statistics
We performed D-statistic-based tests on the SNP chip data from the restricted Greenlandic data set combined with HapMap samples. First, we estimated the allele frequency in each genotyped site separately for the population in each location. Then, we estimated the D statistics asD(H1,H2;H3,H4)=∑i=1M(fiH3−fiH4)(fiH1−fiH2)∑i=1M(fiH3+fiH4−2fiH3fiH4)(fiH1+fiH2−2fiH1fiH2),where H1, H2, H3, and H4 represent populations in the tree (((H1, H2), H3), H4), where H4 is the outgroup, M is the number of sites included, and fiH1 is the allele frequency for population H1 at site i.30 Only sites with information for all four populations were included. Z scores were obtained from the D statistics with SEs based on a “delete m jackknife for unequal m” procedure31 for 5 Mb regions weighted according to the number of SNPs in each block.