Genetic evolution refers to the change in gene frequency, which is the frequency of alleles in a breeding population from generation to generation. This term is used by population genetics for a more specific definition than the one given for the term evolution (?descent with modification over the generations?). Any factor that contributes to such a change can be considered a mechanism for genetic evolution. Those mechanisms include natural selection, mutation, random genetic drift, and gene flow. The first mechanism, natural selection, remains the best explanation for genetic evolution. Once gene frequencies change and adaptation through natural selection occurs, traits that have proven to be most adaptive will be selected again and again through directional selection, or long?term selection of the same trait(s). The second mechanism of genetic evolution is mutation, which occurs spontaneously and regularly and provides new biochemical forms on which natural selection operates. The third genetic evolution mechanism is random genetic drift, which is the change in allele frequency that results from chance and is most common in small populations. The fourth and final genetic evolution mechanism is gene flow, which is more or less the exchange of genetic material between populations species.
References
Kottak, Conrad Phillip. Window on Humanity: A Concise Introduction to Anthropology. New York: The McGraw?Hill Companies, Inc, 2005.
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