Natural selection is the differential survival and reproduction of individuals with particular phenotypes, the physical manifestation of genotypes. Natural selection works only on the phenotypes of individuals. Natural selection produces adaptation when the phenotype is heritable. Natural selection is the most important cause of biological evolution.

Charles Darwin was the creator of the concept of evolution by natural selection. In his 1859 book, On the Origin of Species, the most important book on evolution, Darwin put forth his argument and supported it with multiple examples. Darwin's idea of natural selection was heavily influenced by an essay on human population growth written in 1798 by English economist Thomas Malthus. Malthus pointed out that every organism has the ability to produce more individuals than the environment can support, and that many individuals die without reproducing. Darwin recognized that variation among individuals is always present, and that some individuals with particular...