Artificial selection is a scientific term used to describe the breeding of plants and animals for desirable traits and not necessarily those that would allow the offspring to better survive in the wild. It is also known as selective breeding and unnatural selection. The process can be considered the antithesis of natural selection.
The artificial selection process is relatively easy to accomplish. A specific plant or animal is chosen because it has a specific heritable genetic trait that the breeder desires. The plant or animal is then bred with another of its kind with a similar trait, resulting in offspring with a higher potential to display the specific trait. This cycle can be repeated with the offspring until the specific trait is achieved at the desired level.
Inbred offspring are one of the potential dangers of too much artificial selection. Some traits are so rare that they may only exist in one or two family lines. If the trait is recessive, two members of the same line (relatives) may have to be bred together in order for the trait to be visible (expressed). In animals, this can result in genetic defects and other serious problems.
The results of artificial selection are easy to see. The domestication cycle of dogs (canines) being bred by their owners in order to emphasize less-aggressive traits has gone on for thousands of years, and has resulted in hundreds of different breeds that look almost nothing like their grey wolf ancestors. Dairy cattle are bred in hopes of producing more milk, but some lines now suffer from increased infections and fertility problems. Persian cats that are bred for extremely flat faces often develop respiratory problems and may have trouble eating. All of the listed traits that are bred for do not help the animals survive in the wild, but do make them more desirable to their owners.
Charles Darwin used the term artificial selection twice in his book, On the Origin of Species. In the first reference, he wrote about the complex and beautiful things he believes that humans can create through the process. In the second reference, he used the term to describe the reasons for differences in animal breeds in countries with different development levels. Darwin, however, did not clearly define the term in his book.
