Darwin proposed artificial selection to persuade the most skeptical individuals by using the process of selection performed by humans in the domestication of animals to illustrate the mechanism of natural selection in evolution.
How artificial selection or selective breeding Works
The fundamental principle of artificial selection is to choose and breed individuals that possess traits preferred by humans. Firstly, individuals that exhibit desired traits are selected, while those that do not meet expectations are completely excluded. Their offspring inherit these desired traits, and the above selective process is repeated. As a result of multiple rounds of selection, the desired traits become increasingly prevalent throughout the population until subspecies are produced that meet human preferences. The significant difference between artificial selection and natural selection is the human favored traits and completed elimination of undesired traits. So the purpose of selective breeding is very clear and the process is very fast.
Artificial selection example: selective breeding goldfish
Goldfish are freshwater ornamental fish originated from China. Any type of goldfish can produce fertile offspring when crossbred with wild carp, indicating that goldfish and carp do not experience reproductive isolation. They are different subspecies. In ancient times, carp naturally mutated red scales in the wild to make them more noticeable and easily captured. Later, due to the practice of releasing fish for religious reasons among Buddhists, some people would buy red carp from markets and release them into temple ponds, initiating their semi-domestication.
Subsequently, the emperor of the Southern Song Dynasty built a royal garden in Hangzhou to collect red carp from all over the country, which was then imitated by nobles and officials. The red carp became thoroughly domesticated by artificial feeding and selection. Those with beautiful colors and patterns were selectively bred. During this period, red carp displayed a wider range of colors and patterns, such as orange, gold, white, black and white patches, red and white patches, etc. Their differences from wild carp became even more pronounced. However, they were not yet considered true goldfish because they lacked a tail with more than two branches.
In the Ming Dynasty, the transition from large ponds to pottery tanks and wooden basins allowed people to conveniently control their traits. One notable change was that people began to select red carp with multiple branched tails and bloated body while completely eliminating normal streamlined fish. As the goldfish gracefully swam in water, it tail swung in a mesmerizing rhythm, resembling the ethereal gown of a princess swirling across the ball, which transformed the red carp into true goldfish. During this period, some lost their dorsal fins, some developed red or orange fleshy growths on their heads, and others have large bubbles below their eyes, or protruding eyes. Their colors, patterns and body shape became completely distinct from wild carp.
In the following years, goldfish with different characteristics were crossbred to obtain even more diverse combinations. By the end of the Ming Dynasty, missionaries had brought goldfish from China to various parts of the world.