the Three Population Test, which evaluates a “test” population for evidence of mixture. If the test population is a mixture of lineages related to the comparison populations in two different ways—as African Americans are a mixture of Europeans and West Africans—then the frequencies of the test population’s mutations are expected to be intermediate between those of the two comparison populations. In contrast, if mixture did not occur, there is no reason to expect the frequencies of mutations in the population to be intermediate. Thus the scenarios of mixture and no mixture yield two
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