We reasoned that the difference in DMRs linked to global and local ancestry can be explained both biologically and statistically. Biologically, DNA methylation is more influenced by local genetic variations. Statistically, local ancestry is more variable than global ancestry, which results in a higher power to detect DNA methylation differences and smaller s.d. values in the estimated effect size (Supplementary Fig. 28 and Supplementary Data 8). Even so, we found a significant correlation between local and global ancestry-associated DMRs (Supplementary Fig. 29). Functional enrichment analysis of local ancestry-associated DMRs showed significant enrichment for immune functions across brain regions (hypergeometric, FDR < 0.05; Fig. 5b and Supplementary Data 9), consistent with ancestry-associated DEGs.
