= Population genomics
<Population genomics> studies variation across many genomic regions in sampled <biological populations>. It connects <genome> measurements to ancestry, <gene flow>, demographic history and <natural selection>. Whereas one <genetic locus> gives one partly stochastic history, many loci provide repeated but potentially correlated evidence. <Talking Glossary of Genomic and Genetic Terms by NHGRI>[Genomics and Genome-Wide Association Studies entries]{ref}
For example, comparing <allele frequencies> among populations can reveal broad ancestry patterns while highlighting unusually differentiated regions. Such an outlier is a candidate for explanation, not proof of local adaptation: sampling, linked variation and demographic events also affect the comparison. A sampling design must specify who was included, and reference-dependent sequencing errors can imitate biological differences if they differ systematically between groups.
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