This chapter examines several examples of genetic admixture in human populations and shows how both genetic data and cultural information are critical to understanding this phenomenon. Population geneticists use the term admixture to refer to the exchange of genes that occurs when populations come into contact that had hitherto been mostly separated for a long period of time. There are many examples of admixture in human history across the world. Although simplistic, admixture models allow us to roughly quantify the relative amounts of ancestry from two populations that encountered one another in the past and merged to produce an admixed descendant population. Admixture rates vary somewhat from population to population, which is expected given local differences in the history of contact and cultural factors affecting gene flow. The admixture estimates for African Americans refer to estimates derived from entire population samples and thus give estimates of average admixture by community.