Admixture in human populations
The inter-breeding amongst the two or more populations which were previously isolated from each other for the geographical or the cultural reasons. Population admixture can be a source of the spurious connection between diseases and alleles which are both more common in one ancestral population than the others. Though, populations which have been admixed for numerous generations might be useful for mapping the disease genes, because of the spurious associations tend to be dissipated much more rapidly than true associations in consecutive generations of random mating.