The combination of the various population-genetic factors with the pragmatic factors affecting the choice of study populations has uniquely favored European populations in GWA studies. These factors provide part of the explanation for two outcomes: (1) European GWA studies have produced many successes that can be replicated in different sets of individuals from the same European population as that in which the association was originally detected; (2) associations in one population of European descent are often replicable in other European populations, sometimes in groups that are quite geographically distant within the European continent.
