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Selective breeding (also called artificial selection) is the process by which humans use animal breeding and plant breeding to selectively develop particular phenotypic traits (characteristics) by choosing which typically animal or plant males and females will sexually reproduce and have offspring together.
The existence of limits in artificial selection experiments was discussed in the scientific literature in the 1940s or earlier. [1] The most obvious possible cause of reaching a limit (or plateau) when a population is under continued directional selection is that all of the additive-genetic variation (see additive genetic effects) related to that trait gets "used up" or fixed. [2]
The red junglefowl (Gallus gallus), often believed to be an ancestor of the domestic chicken.. Most animals are tuned to modern life by artificial selection. This is either due to the pressure of early hunter-gatherers' attempts to stabilise the food supply, which resulted in the existence of domesticated farm animals, or domestication of pets which are useful to humans. [2]
A highly indicative test of changes in allele frequencies is the QTL sign test, and other tests include the Ka/Ks ratio test and the relative rate test. The QTL sign test compares the number of antagonistic QTL to a neutral model, and allows for testing of directional selection against genetic drift . [ 11 ]
The process of artificial selection has had a significant impact on the evolution of domestic animals. For example, people have produced different types of dogs by controlled breeding. The differences in size between the Chihuahua and the Great Dane are the result of artificial selection.
Unwittingly, humans have carried out evolution experiments for as long as they have been domesticating plants and animals. Selective breeding of plants and animals has led to varieties that differ dramatically from their original wild-type ancestors. Examples are the cabbage varieties, maize, or the large number of different dog breeds.
Here, simulations of evolution using evolutionary algorithms and artificial life started with the work of Nils Aall Barricelli in the 1960s, and was extended by Alex Fraser, who published a series of papers on simulation of artificial selection. [10] Artificial evolution became a widely recognised optimisation method as a result of the work of ...
The level of gene flow among populations can be estimated by observing the dispersal of individuals and recording their reproductive success. [4] [11] This direct method is only suitable for some types of organisms, more often indirect methods are used that infer gene flow by comparing allele frequencies among population samples.
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