Artificial selection refers to genetic changes in populations that result from human choice. Artificial selection resembles natural selection in these ways:

- It is a process that occurs in populations.

- The population must have genetic variability from which selection, natural or artificial, can choose.

- As a result of their genetic characteristics, some individuals in the population reproduce more than other individuals.

- As a result of differential reproduction of individuals, the characteristics of the population change.

In natural selection, the individuals that reproduce the best are those that are best suited to the natural conditions of their habitat, and the social conditions of their populations. In artificial selection, success depends entirely on human will.

Charles Darwin used artificial selection as a model for natural selection. Some writers have claimed that artificial selection was just a metaphor for natural selection, but it was more. Natural populations contain genetic variability, on which either natural or artificial selection can act. It was artificial selection that allowed Darwin to demonstrate that this variability did, in fact, exist. His most striking example was the domestic pigeon. Different breeds of domestic pigeon had different outlandish characteristics:

Some had inflatable throats; some had ornate feathers; others could tumble in the air while flying. Darwin cited the historical fact that all of these pigeons had been bred, within recent centuries, from wild rock doves (Columba livia). Crossing any two of the domesticated breeds of pigeons produced offspring that resembled the wild rock dove. Artificial selection proved what extreme changes were possible, starting with just the genetic variability that exists in wild populations.

Artificial selection can have practical value or appear almost whimsical. Artificial selection was entirely responsible for producing the many species of crop plants and livestock animals from wild ancestors. Silviculturists have bred trees that rapidly produce strong wood, and horticulturists have bred garden flowers, bushes, and fruit and ornamental trees that are very useful in the human landscape. Some crop and garden plants have been so altered by artificial selection that they cannot survive in the wild. Garden tomatoes, for example, cannot even hold their heavy fruits off of the ground, where they rot if left unattended. Seedless fruits, from oranges to watermelons, can reproduce only through cuttings, which would seldom occur without human intervention. Some livestock animals, and many pets, have been bred into outlandish forms. Tiny hairless dogs and cats are an extreme example. . .

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