Causes of Population Stratification
The basic cause of population stratification is nonrandom mating between groups, often due to their physical separation (e.g., for populations of African and European descent) followed by genetic drift of allele frequencies in each group. In some contemporary populations there has been recent admixture between individuals from different populations, leading to populations in which ancestry is variable (as in African Americans). Over tens of generations, random mating can eliminate this type of stratification. In some parts of the globe (e.g., in Europe), population structure is best modeled by isolation-by-distance, in which allele frequencies tend to vary smoothly with location.
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Famous quotes containing the word population:
“The paid wealth which hundreds in the community acquire in trade, or by the incessant expansions of our population and arts, enchants the eyes of all the rest; the luck of one is the hope of thousands, and the bribe acts like the neighborhood of a gold mine to impoverish the farm, the school, the church, the house, and the very body and feature of man.”
—Ralph Waldo Emerson (1803–1882)